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2013 STE-QUEST WORKSHOP BOOK OF ABSTRACTS 22-23 May 2013 ESTEC, room Newton Keplerlaan 1, Noordwijk - The Netherlands http://sci.esa.int/ste-quest-ws2013 1 Einstein’s theory of general relativity is a cornerstone of modern physics. It is used to describe the flow of time in presence of gravity, the motion of bodies from satellites to galaxy clusters, the propagation of electromagnetic waves in the presence of massive bodies, and the dynamics of the universe as a whole. Although very successful so far, general relativity, as well as numerous other alternative or more general theories of gravitation, are classical theories. As such, they are fundamentally incomplete as they do not include quantum effects. A theory solving this problem would represent a crucial step towards the unification of all fundamental forces of Nature. Several approaches have been proposed and are currently under investigation (e.g. string theory, quantum gravity, extra spatial dimensions) and all of them tend to lead to tiny violations of basic principles. Therefore, a full understanding of gravity will require observations or experiments able to determine the relationship between gravity and the quantum world. This topic is a prominent field of activity and includes the current studies of dark energy. Space-Time Explorer and QUantum Equivalence Space Test (STE-QUEST, http://sci.esa.int/ste-quest) is a mission conceived to test the different aspects of the Einstein Equivalence Principle by using high-stability and accuracy atomic sensors. Submitted in reply to the 2010 Call for Medium-size Missions for the Cosmic Vision plan, STE-QUEST was recommended by the ESA advisory structure and finally selected for an assessment study. Scope of the workshop is to present and discuss with the scientific community the STE-QUEST science case and the progress achieved in the frame of the mission and instruments studies. The STE-QUEST Study Science Team Kai Bongs Philippe Bouyer Luigi Cacciapuoti Luciano Iess Arnaud Landragin Philippe Jetzer Ernst Rasel Stephan Schiller Uwe Sterr Guglielmo Tino Philip Tuckey Peter Wolf Birmingham University, United Kingdom Institut d'Optique, France ESA, The Netherlands Università "La Sapienza", Italy Observatoire de Paris, France Zurich University, Switzerland Universität Hannover, Germany Heinrich-Heine-Universität Düsseldorf, Germany PTB, Germany Firenze University, Italy Observatoire de Paris, France Observatoire de Paris, France 2 Scientific Program 22 May 2013 08:30 Registration STE-QUEST Science I (Chair: P. Wolf) 09:30 STE-QUEST and the Einstein Equivalence Principle (S. Schiller) 10:00 Extended Theories of Gravity and Fundamental Physics (S. Capozziell o, p.14) 10:30 Coffee Break 11:00 The Cosmological Context (P. Binetruy, p.59) 11:30 Quantum Mechanics at the Interface with Gravity (W. Schleich, p.26) 12.00 On the Potential of STE-QUEST Clocks for Relativistic Geodesy (R. Bondarescu, p.27) 12:20 Lunch Break Mission Design and Instruments I (Chair: U. Sterr) 13:50 Mission Design (M. Gehler) 14:10 The Atomic Clock (P. Tuckey) 14:40 STE-QUEST Differential Atom Interferometer (E. Rasel, p.32) 15:10 Time and Frequency Transfer Links (P. Wolf) 15:30 Coffee Break 16:00 Features of the STE-QUEST S/C Design with Focus on Instrument Interfaces, Telecommand & Data Handling, and Science Links (F. Beck, p.55) 16:20 STE-QUEST: TAS Assessment Study Main Outcomes (A. Ferri, p.57) 16.40 Programmatic Aspects (A. Parmar) 17.00 Space clocks and Fundamental Tests (C. Salomon) 17:30 Posters Session 19:00 Bus to Hotels 3 23 May 2013 STE-QUEST Science II (Chair: P. Jetzer) 09:00 Tests of Lorentz Symmetry with STE-QUEST (J. Tasson, p.25) 09:30 Quantum Mechanics and the Equivalence Principle (D. Giulini, p.62) 10.00 Spacecraft Clocks and General Relativity (R. Angelil, p.20) 10:20 STE-QUEST - Geodetic Mission for Terrestrial and Celestial Reference Frame Realization (D. Svehla, p.61) 10.40 Coffee Break Mission Design and Instruments II (Chair: E. Rasel) 11:00 Fundamental Physics Tests by Atom Interferometry (M. Kasevich) 11.30 Atom Interferometry in Free Fall (A. Landragin) 12.00 STE-QUEST Mission: Atom Interferometer Performance Assessment and Error Estimations (C. Schubert, p.36) 12:20 Frequency Comb on a Sounding Rocket. Technology demonstration and Prototpye LPI Test (R. Holtzwarth) 12.50 Lunch Break 14.00 Open Discussion Chaired by the STE-QUEST Study Science Team Mission Design and Instruments III (Chair: S. Schiller) 15.00 MOLO: A Microwave from Optical Local Oscillator (U. Sterr) 15.20 Optical Frequency Divider based on Passively Mode-locked Diodepumped Solid-state Laser Technology (S. Lecomte, p.18) 15.40 Coffee Break 16.00 Development of Atomic Clocks and Frequency Transfer Techniques at Three Laboratories around Tokyo Area (Y. Hanado, p.53) 16.30 The Yb Lattice Clock (and others!) at NIST for Space-Based Applications (C. Oates, p.38) 17.00 Towards Precision Measurements in Space with Clocks and Atom Interferometers (N. Yu, p.13) 17.30 Closing Remarks 4 Posters Session Name Institution Chen, X. Peking University, China 1 Mueller, H. UC Berkeley, US 2 Yu, N. Bulyzhenkov, I. Stefanov, A. Laurent, P. Schärer, A. Gaaloul, N. Zhang, S. Hartwig, J. Arnold, A. Bawamia, A. Chen, Q-F Chen, Q-F Schuldt, T. Krutzik, M. Schediwy, S. Ernsting, I. Delva, P. Roura, A. Chiodo, N. Jet Propulsion Laboratory, US Lebedev Physics Institute, Russian Federation University of Bern, Institute of Applied Physics, Switzerland LNE-SYRTE, Observatoire de Paris, France Institute for Theoretical Physics, University of Zürich, Switzerland IQO, Leibniz University, Hanover, Germany National Time Service Center, Chinese Academy of Science, China IQO, Leibniz University, Hanover, Germany University of Strathclyde, UK Ferdinand-BraunInstitut, Germany Heinrich-HeineUniversität Düsseldorf, Germany Heinrich-HeineUniversität Düsseldorf, Germany DLR-Institute of Space System, Germany Humboldt- Universität zu Berlin, Germany University of Western Australia, Australia Heinrich-HeineUniversität Düsseldorf, Germany SYRTE / Observatoire de Paris / UPMC, France University of Ulm, Germany SYRTE / Observatoire de Paris / UPMC, France Board n. Abstract Title Proposal for Atom Cooling Approach in Space and a Cold Atom Experimental System in Chinese Space Station – p.11 Testing Lorentz Invariance and Einstein’s Equivalence Principle – p.12 Towards Precision Measurements in Space with Clocks and Atom Interferometers – p.13 Continuous Material Space with Local Equivalency of Inertial and Gravitational Mass Densities can be Justified by Precise Clocks – p.15 3 4 5 Microwave Clock Cavity Simulation for the STE-QUEST Mission – p.16 6 PHARAO: A Cold Cesium Clock for Space Applications p.23 7 Testing Chameleon Scalar Fields With STE-QUEST – p.24 8 Chip-based BEC Interferometry in Microgravity – p.28 9 Introduction of Time and Frequency Package for China Space Station Project – p.30 10 Atom Interferometry for Inertial Sensing and Fundamental Physics at the IQO – p.31 11 Grating Chips for Quantum Technologies – p.33 Compact Semiconductor Laser Modules Designed for Precision Quantum Optical Experiments in Space – p.35 Tests of Irradiation Robustness of a Fabry Perot Resonator Comprising High-finesse Fused Silica Mirrors and a ULE Spacer – p.41 12 13 14 Development of a Robust Demonstrator for an Ultra-stable Optical Cavity for the STE-QUEST Mission – p.42 15 STE-QUEST Atom Interferometer (ATI) Payload Overview – p.44 Laser System for Dual Species Interferometry with 87Rb and 85Rb on STE-QUEST – p.46 An Optical Link for the ACES and STE-QUEST Missions in Western Australia –p. 48 16 17 18 Microwave Generation from Optical Frequency Combs – p.50 19 Time and frequency transfer with the ESA/CNES ACESPHARAO mission – p.51 20 Overcoming loss of contrast in atom interferometry due to gravity gradients – p.52 21 Towards a Free Space Satellite to Ground Coherent Optical Link – p.56 5 Feldmann, T. Gill, P. Schubert, C TimeTech GmbH National Physical Laboratory IQO, Leibniz University, Hanover, Germany Microwave Link Design and Optical Link Design for Future Scientific Space Missions – p.58 Towards a Space-qualified High-finesse Cavity for Optical Clocks – p.60 22 23 STE-QUEST Mission: Atom Interferometer Performance Assessment and Error Estimations – p. 36 24 6 List of Registered Participants Name Aben, Guido Email [email protected] Institution AARNet p/l Country Australia Angelil, Raymond [email protected] ITP, University of Zurich Switzerland Arnold, Aidan [email protected] University of Strathclyde United Kingdom Bawamia, Ahmad [email protected] Ferdinand-Braun-Institut Germany Beck, Felix [email protected] ASTRIUM Germany Binetruy, Pierre [email protected] APC, Universite Paris Diderot France Bondarescu, Mihai [email protected] Universitatea de Vest Romania Bondarescu, Ruxandra [email protected] University of Zurich Switzerland Bongs, Kai [email protected] [email protected] r University of Birmingham United Kingdom LP2N - IOGS France Bouyer, Philippe Bulyzhenkov, Igor [email protected] Cacciapuoti, Luigi [email protected] Moscow Institute of Physics and Technology European Space Agency Capozziello, Salvatore [email protected] Università di Napoli Federico II Italy Carraz, Olivier [email protected] ESA - ESTEC - EOP/SF Netherlands Carvalho, Carla Sofia Chiodo, Nicola [email protected] Delva, Pacôme [email protected] Duev, Dmitry [email protected] CAAUL, University of Lisbon Heinrich-Heine-Universität Düsseldorf Peking University SYRTE, CNRS UMR8630, UPMC.Observatoire de Paris Observatoire de Paris / UPMC Joint Institute for VLBI in Europe Portugal Chen, Xuzong [email protected] [email protected] [email protected] Dufour, Carole carole.dufour@thalesaleniaspace. com Thales Alenia Space France Ernsting, Ingo [email protected] Feldmann, Thorsten [email protected] antonella.ferri@thalesaleniaspace. com Chen, Qun-Feng Ferri, Antonella Gaaloul, Naceur [email protected] Gehler, Martin [email protected] Giese, Enno [email protected] Gill, Patrick [email protected] Giulini, Domenico [email protected] Hanado, Yuko Hartwig, Jonas [email protected] Guerlin, Christine Gürlebeck, Norman Thales Alenia Space IQO, Leibniz University, Hanover, Germany ESA Institut für Quantenphysik, Universität Ulm National Physical Laboratory ZARM Bremen and University of Hannover davide.granasomministrato@thalesaleniaspace .com [email protected] [email protected] [email protected] Granà, Davide Heinrich-Heine-Universität Düsseldorf TimeTech GmbH 7 Russian Federation Netherlands Germany China France France Netherlands Germany Germany Italy Germany Netherlands Germany United Kingdom Germany Wintime SpA Italy LKB France ZARM, University Bremen Germany NICT Japan Institute for Quantumoptics Germany Hauth, Matthias [email protected] Humboldt-Universität zu Berlin Germany Heske, Astrid ESA ESTEC Netherlands ASTRIUM Germany Holzwarth, Ronald [email protected] Gerald.Hechenblaikner@astrium. eads.net [email protected] Menlo Systems GmbH Germany Iess, Luciano [email protected] Università La Sapienza Italy Jetzer, Philippe [email protected] University of Zurich Switzerland Kasevich, Mark Stanford University United States Humboldt-Universität zu Berlin Germany Le Goff, Roland [email protected] [email protected] [email protected] Sodern France Lambiase, Gaetano [email protected] University of Salerno Italy Landragin, Arnaud [email protected] SYRTE, Observatoire de Paris France Lecomte, Steve [email protected] CSEM Switzerland Leon Hirtz, Sylvie [email protected] France Lundgren, Andrew [email protected] CNES Albert Einstein Institut Hannover Thales Alenia Space Italy Italy ZARM, University of Bremen Germany ESA Netherlands UC Berkeley Institut für Experimentalphysik Heinrich-Heine-Universität Düsseldorf National Institute of Standards and Technology Joint Institute for VLBI in Europe (JIVE) Leibniz University Hannover United States University of Ulm Laboratoire Kastler Brossel, Ecole Normale Supérieure, Paris University of Western Australia Heinrich-Heine-Universität Düsseldorf Institut für Quantenphysik, Universität Ulm Gottfried Wilhelm Leibniz Universität Hannover DLR - Institute of Space Systems Germany Thales TRT France Institute for Theoretical Physics Switzerland National Physical Laboratory University of Bern, Institute of Applied Physics Physikalisch-Technische Bundesanstalt United Kingdom Hechenblaikner, Gerald Krutzik, Markus Miquel Espana, Cesar alessandra.marcer@thalesaleniasp ace.com [email protected] [email protected] Mueller, Holger [email protected] Nevsky, Alexander [email protected] Oates, Chris [email protected] Pogrebenko, Sergei [email protected] Rasel, Ernst Maria [email protected] Roura, Albert [email protected] Salomon, Christophe [email protected] Schediwy, Sascha [email protected] Schiller, Stephan [email protected] Schleich, Wolfgang [email protected] Schubert, Christian [email protected] Schuldt, Thilo [email protected] Marcer, Alessandra Milke, Alexander Schärer, Andreas [email protected] m [email protected] Shemar, Setnam [email protected] Stefanov, Andre [email protected] Sterr, Uwe [email protected] Svehla, Drazen [email protected] Tasson, Jay [email protected] Schwartz, Sylvain Germany Germany United States Netherlands Germany France Australia Germany Germany Germany Germany Switzerland Germany Germany Carleton College 8 United States Dipartimento di Fisica, LENS, Università Firenze LNE-SYRTE, Observatoire de Paris LaserLaB VU university Tino, Guglielmo M. [email protected] Tuckey, Philip [email protected] Vassen, Wim [email protected] Waller, Pierre [email protected] [email protected] [email protected] [email protected]. net Wicht, Andreas Wille, Eric Williams, Michael Wolf, Peter [email protected] Yu, Nan [email protected] Zhang, Shougang [email protected] Zelan, Martin [email protected] France Netherlands ESA/ESTEC Netherlands Ferdinand-Braun-Institut Germany ESA Netherlands Astrium Ltd. United Kingdom Observatoire de Paris - LNE CNRS - UPMC Jet Propulsion Laboratory National Time Service Center, Chinese Academy of Science SP Technical Research Institute of Sweden 9 Italy France United States China Sweden Abstracts 10 Proposal for Atom Cooling Approach in Space and a Cold Atom Experimental System in Chinese Space Station Xuzong Chen Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China [email protected], Homepage:http://iqe.pku.edu.cn/ Abstract. The talk introduces the proposal for atom cooling approach in space and a cold atom experimental system in Chinese space station. In the first part, the talk analyzes the relation between the critical temperature for quantum gas with the trap frequency, and proposes two approaches to cool the quantum gas to pK temperature in space. In the second one, the talk introduces the design for the cold atom experimental system on Chinese space station, which is planned to be launched in 2018, the challenges for the technology of lasers and electronics system are commented,. In the third one, the talk introduces the six foundamental physics experiments based on quantum gas will be carried in the cold atom plateform in the Chinese space station. REFERENCES Xinxing Liu, Xiaoji Zhou，Wei Xiong, Thibault Vogt, and Xuzong Chen, Rapid nonadiabatic loading in an optical lattice, Phys. Rev. A 83, 063402 (2011). Bo Lu, Thibault Vogt, Xinxing Liu, Xu Xu, Xiaoji Zhou, and Xuzong Chen, Cooperative scattering measurement of coherence in a spatially modulated Bose gas, Phys. Rev. A 83, 051608(R) (2011). Xinxing Liu, Xiaoji Zhou, Wei Zhang, Thibault Vogt, Bo Lu, Xuguang Yue, and Xuzong Chen, Exploring multiband excitations of interacting Bose gases in a one-dimensional optical lattice by coherent scattering, Phys. Rev. A 83, 063604 (2011). Thibault Vogt, Bo Lu, XinXing Liu, Xu Xu, Xiaoji Zhou, and Xuzong Che, Mode competition in superradiant scattering of matter waves, Phys. Rev. A 83 053603 (2011) Jun Duan, Xianghui Qi, Xiaoji Zhou, and Xuzong Chen, Detection of saturated absorption spectroscopy at high sensitivity with displaced crossovers, Opt. Lett. 36,561 (2011). 11 Testing Lorentz Invariance and Einstein’s Equivalence Principle Michael A. Hohensee and Holger Müller Physics Department, University of California, Berkeley, CA 94720 The Einstein equivalence principle holds that the influence of gravity is the same for all systems, e.g. protons, neutrons, or electrons, be they normal matter or antimatter [1]. The quantum weak equivalence principle (QWEP) project will test the equivalence principle by matter-wave interferometry, making use of a microgravity environment to attain high sensitivity. We will discuss theoretical and experimental aspects of this experiment. While the equivalence principle has been verified with high precision using normal matter [2], direct experimental tests for antimatter are ongoing. We work in the context of the standard model extension, an effective field theory that describes multiple paths by which the equivalence principle can be violated. This theory specifically includes a ‘hidden’ limit, where the equivalence principle holds for free particles of normal matter, but not for their antimatter counterparts [3]. We find that such hidden violations can nevertheless be detected using normal matter by observing the motion of bound systems of particles, in direct proportion to the bound kinetic energy within such systems [4,5]. We show that QWEP would not only improve existing limits on EEP-violation for normal matter, but could also improve indirect limits on antimatter-specific EEP-violation. The accuracy of atom interferometers is directly determined by its ability to suppress systematic effects. This can be achieved through judicious choice of interferometer geometry and the atom-optics used. We will compare geometries based on Raman transitions, Bragg diffraction, double diffraction, and Bloch oscillations, and new technologies that have been developed recently by us. REFERENCES [1] [2] [3] [4] [5] C.W. Misner, K.S. Thorne, and J.A. Wheeler, Gravitation, (W.H. Freeman and Company, New York, USA, 1973). C.M. Will, Theory and Experiment in Gravitational Physics, (Cambridge University Press, Cambridge, U.K.; New York, USA. 1993), 2nd edition. V.A. Kostelecky and J.D. Tasson, Phys. Rev. D 83, 016013 (2010). M.A. Hohensee, S. Chu, A. Peters, and H. Müller, Phys. Rev. Lett. 106, 151102 (2011). M.A. Hohensee and H. Müller, to be published. 12 Towards Precision Measurements in Space with Clocks and Atom Interferometers Nan Yu Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA [email protected] Abstract. Space provides a unique experimental environment to explore the fundamental physics and quantum phenomena that are not possible in terrestrial research labs. The favorable space conditions include microgravity and low vibrations that are particularly attractive for cold atom based experiments. The space platforms also permit investigations of physical phenomena over large spatial, velocity, and gravitational variations. In this talk, we will summarize our efforts in developing and maturing relevant technologies for spacebased fundamental physics experiments. We have been focusing our research and development activities in two main topical areas – advanced frequency standards and atom interferometers. In the area of clocks, we will briefly describe Hg+ ion clocks, the ground LITS clocks and their participation of the ACES ground clock network, and the more compact space clock for deep space. We will then present our approaches on a miniature optical clock and a coherent optical transponder for optical frequency link. In the atom interferometer area, we will report our progress in developing the transportable gravity gradiometer. We will also briefly introduce the CAL project, an ultra-cold atom facility on ISS, its science objectives and implementation. 13 Extended Theories of Gravity and Fundamental Physics S. Capozziello,G. Lambiase 1 Universita' di Napoli "Federico II" Complesso Universitario di Monte S. Angelo Via Cinthia, Ed. N I-80126 Napoli - Italy [email protected] Abstract. Extended theories of gravity are formulated with the aim to address problems like Dark Energy and Dark Matter at infrared scales and the problem of quantization of gravity at ultraviolet scales. The paradigm consists in adding high order terms in curvature invariants and/or scalar fields in the Hilbert-Einstein action with the goal to cure shortcomings of standard general relativity. We discuss connections of these theories with fundamental physics, in particular, in view of testing the equivalence principle at quantum level. STE-QUEST could provide the experimental tools to probe viable models. 14 Continuous Material Space with Local Equivalency of Inertial and Gravitational Mass Densities can be Justified by Precise Clocks I. Bulyzhenkov Moscow Institute of Physics & Technology and Lebedev Physics Institute RAS, [email protected], [email protected] Abstract. Non-empty space paradigm for reality can be described in mathematical terms of Einstein’s General Relativity (GR), but with continuous inertial masses integrated into the very spatial structure of their gravitational fields. Joint geometrization of the continuous particle and its GR field reveals the physical meaning of 1902 Ricci scalar R ≡ gµνRµν = 8πG(µp + µa)/c2 as the scalar mass density of material space, which is the flat 3D section of the curved 4D pseudo-Riemann manifold. Such a material space is continuously filled everywhere by equal passive (inertial µp) and active (gravitational µa) mass-densities causing local metric stress, goo≠1, or the gravitational potential W(x)≡ - c2ln(1/√goo) = - c2ln[1+ (Gm1/ c2|x-a1 |) +…+ (Gmn/ c2|x-an |)]. The Principle of Equivalence µp ≡(∇W)2 /4πG c2 =∇2W /4πG≡ µa provides an additional equation for metric component goo that makes GR of nonempty space a self-contained theory without needs in the Newton weak-field reference. The emptyspace GR predicts Schwarzschild time dilation (dτ-dt)/dt≡√goo -1=φ(1- φ/2c2)/ c2 in negative weak potential φ, while non-empty space relativistic physics corresponds to another time dilation, φ(1+ φ/2c2)/c2. The Newton potential φ is time-varying in the Earth-Sun-Moon system and precise clocks can distinguish non-empty space reality from the empty space model with non-physical delta-operator density of particles. Would time-dilation measurements justify the non-empty space paradigm in practice, than 3D space keeps strictly Euclidean subinterval (due to inherent 4D metric symmetries) in the pseudo-Riemann metric formalism of Einstein’s gravitation. Such a flat space in strong fields is required for quantization and for further unification of metric gravity with other forces in the quantum world. REFERENCES Einstein, A., Infeld, I., and B. Hoffmann, Ann. Math. 39, 65 (1938). Hilbert, D., Nachrichten K. Gesellschaft Wiss. Gøttingen, Math-Phys. Klasse, Heft 3, 395 (1915). Mie, G., Ann. Phys. (Berlin) 37, 511 (1912); Ann. Phys. (Berlin) 39, 1 (1912); Ann. Phys. (Berlin) 40, 1 (1913). Schwinger, J., in Quantum, Space and Time - The Quest Continues, Ed. by A. O. Barut, A. Van der Merwe, and J.P. Vigier (Cambridge Univ. Press, Cambridge, 1984), pp. 620-627. Tonnelat, M.-A., Les Principles Theorie Electromagnetique et Relativite (Masson, Paris, 1959). Schwinger, J., in Quantum, Space and Time - The Quest Continues, Ed. by A. O. Barut, A. Van der Merwe, and J.P. Vigier (Cambridge Univ. Press, Cambridge, 1984), pp. 620-627. Bulyzhenkov, I. E., Int. J. Theor. Phys. 47, 1261-1269, 2008. Bulyzhenkov, I. E., J. Supercond. Nov. Magn. 22, 723-727, 2009. Bulyzhenkov, I. E., J. Supercond. Nov. Magn. 22, 627-629, 2009. Bulyzhenkov, I. E., Applied Physics (in Russian N6, 205-212 (2011). Bulyzhenkov, I. E., Engineering Physics (in Russian) N7, 3-9 (2011). Bulyzhenkov, I. E., J. Modern Physics, 3, N.10, 1465-1478 (2012). 15 Microwave Clock Cavity Simulation for the STE-QUEST Mission A. Stefanov1 1 University of Bern, Institute of Applied Physics, Sidlerstrasse 5, CH-3012 Bern [email protected] Abstract. One of the fundamental limitations on the accuracy of a microwave atomic clock is given by the non uniform distribution of the field within the microwave cavity. In an atomic standard with moving atoms, the atoms interact twice with the microwave in a cavity. Due to the residual divergence of the atomic beam, the interaction is not guaranteed to occur twice at the very same position within the cavity. Thus in the presence of phase gradients, the atoms will be subjected to two interactions with a phase difference ∆φ. In a Ramsay interferometer, two dephased interactions at the clock transition frequency separated by a time T are interpreted as a frequency shift of ∆f = ∆φ /2πT. Hence a phase gradient leads directly to a frequency shift of the frequency standard as a function of the atomic trajectories, and the accuracy of the standard is ultimately limited by the knowledge of both the phase distribution and the atomic trajectories distribution. The first action to reduce this source of uncertainty is to design the microwave cavity such that the phase gradients are minimized. The remaining phase gradient needs then to be estimated for the final uncertainty budget. The phase of the field can however only be probed with sufficient accuracy by the atoms themselves. Therefore measurements of frequency shifts for varying the atomic trajectories have to be performed and a model of the phase gradients has to be used to fit those measurements. For thermal beam Cs standards, the phase gradients due to losses in the cavity walls are minimized by designing the cavity such that the atoms are subjected to two travelling waves coming from opposite directions [1]. The end-to-end cavity phase shift resulting from a cavity difference due to an asymmetry of the cavity can be evaluated by reversing the atomic beam [2]. In vertical atomic fountains the evaluations of the phase gradient have been done based on the theory developed in [3] and [4]. Recent measurements on vertical atomic fountains showed good agreement with this theory [5–7]. One can distinguish two types of phase gradients, the ones originating from an imperfection of the cavity construction and the ones intrinsic to the design. The first ones cannot be numerically evaluated and can only be revealed by experiment. The second category of phase gradients can be evaluated analytically only for very simple geometries and in general require numerical computations. We present here a full 3D Finite Element Method (FEM) computation of the phase gradient for a cavity close to the one planned to be used for the clock of the STE-QUEST mission. The simulations are done using the RF module of the COMSOL software. In the first part we present simulations done for cylindrical geometries, which can be compared with already published results from numerical simulations and analytical evaluations. The purpose is to validate the simulation method. In a second part we present results for the design of the STE-QUEST cavity, both for eigenmode simulations of the cavity only and for port excitation computations (figure 1). 16 FIGURE 1. Map of the norm (links) and of the phase (right) of the longitudinal component of the H field when excited at resonance by the input port slit at the top of the cavity. The phase spans a range of spans 0.13 mrad. ACKNOWLEDGMENTS This research was supported by the Swiss Space Office. REFERENCES [1] A. de Marchi, J. Shirley, D. J. Glaze, and R. Drullinger, “A new cavity configuration for cesium beam primary frequency standards,” IEEE Transactions on Instrumentation and Measurement, vol. 37, no. 2, pp. 185–190, Jun. 1988. [2] C. Audoin and J. Vanier, The quantum physics of atomic frequency standards. Adam Hilger, 1989. [3] R. Li and K. Gibble, “Phase variations in microwave cavities for atomic clocks,” Metrologia, vol. 41, no. 6, pp. 376–386, Dec. 2004. [4] R. Li and K. Gibble, “Evaluating and minimizing distributed cavity phase errors in atomic clocks,” Metrologia, vol. 47, no. 5, pp. 534–551, Oct. 2010. [5] J. Guéna, R. Li, K. Gibble, S. Bize, and A. Clairon, “Evaluation of Doppler Shifts to Improve the Accuracy of Primary Atomic Fountain Clocks,” Physical Review Letters, vol. 106, no. 13, pp. 1–4, Apr. 2011. [6] R. Li, K. Gibble, and K. Szymaniec, “Improved accuracy of the NPL-CsF2 primary frequency standard: evaluation of distributed cavity phase and microwave lensing frequency shifts,” Metrologia, vol. 48, no. 5, pp. 283–289, Oct. 2011. [7] S. Weyers, V. Gerginov, N. Nemitz, R. Li, and K. Gibble, “Distributed cavity phase frequency shifts of the caesium fountain PTB-CSF2,” Metrologia, vol. 49, no. 1, pp. 82–87, Feb. 2012. 17 Optical Frequency Divider based on Passively Mode-locked Diode-pumped Solid-state Laser Technology S. Lecomte, S. Kundermann, E. Portuondo-Campa, G. Buchs Centre Suisse d’Electronique et de Microtechnique, Jaquet-Droz 1, 2000 Neuchâtel, Switzerland [email protected] Abstract. In order to improve the frequency stability of the STE-QUEST cold atom atomic clock system over the PHARAO clock system of the ACES (Atomic Clock Ensemble in Space) mission, a microwave optical local oscillator (MOLO) will replace the quartz-based local oscillator. Key elements of the MOLO are a cavity-stabilized continuous-wave laser and an optical frequency comb. Here we present an optical frequency comb based on passively mode-locked diode-pumped solid-state laser (DPSSL) technology which appears to be very promising for fulfilling the mission constraints. Optical frequency combs are usually based on Ti:Sapphire or fiber laser technology. Because of its complex pump laser system and low power efficiency, Ti:Sapphire is a prohibitive technology for space applications. Fiber lasers are therefore more attractive. For self-referenced fiber lasers (at 1 or 1.5 µm), an architecture based on fiber oscillator plus fiber amplifier is necessary. However, a major concern for space-qualification of fiber lasers is the radiation hardness of the doped fiber which is a well-known challenge [1]. So far no appropriate solution has been demonstrated for solving this problem. In order to get an optical frequency comb fully compatible with space constrains, we investigate an alternative technology based on passively mode-locked diode-pumped solid-state laser (DPSSL) technology. Such lasers are pumped with the same diode type as fiber lasers. These pump diodes are Telcordia-qualified with impressive robustness and mean-time-to-failure (MTTF). The laser gain medium is based on Yb- or Er-doped crystals or glasses, and mode-locking is achieved passively with a semiconductor saturable absorber mirror (SESAM). Finally the laser cavity is made of mirrors with free-space beam propagation (see for example ref [2]). These lasers are inherently low noise because of the low loss / low gain laser cavity (similar to Ti:sapphire lasers but opposite to fiber lasers which show high-gain / high loss) that limits the impact of fundamental noise coming from spontaneous emission [3]. Typical laser performances are output powers above 100 mW, clean transform-limited soliton pulses in the 100 - 200 fs range and repetition rates in the order of 10’s to 100’s of MHz. Because of the high power level directly available from the oscillator the fiber amplifier can be avoided, hence simplifying the system architecture. CSEM investigated several key aspects of this technology for space qualification. Proton radiation hardness of different gain media has been tested and no detrimental effect has been detected. Pulse timing jitter of such free-running lasers has been measured with sub-100 attoseconds integrated jitter [from 10 kHz to 5 MHz] as well as relative intensity noise below -156 dBc/Hz validating the very lownoise operation. Furthermore, state-of-the-art ultra-low phase-noise microwave generation has been demonstrated [4]. Also, vibration tests have been performed and showed promising results. Indeed, the laser (which is not engineered for space) already successfully passed a demanding Ariane-5 launch acceptance test. All these results will be presented at the workshop as well as the planned tests to be performed until the end of the assessment study. So far this approach appears to be an ideal solution for a space-qualified optical frequency comb. ACKNOWLEDGMENTS The authors would like to thank Rüdiger Paschotta from RP Photonics for collaboration in the timing jitter measurements. Financial support from the Canton of Neuchâtel, the Swiss Space Office and the Prodex office is acknowledged. 18 REFERENCES [1] Lezius M., Predehl K., Stöwer W., Türler A., Greiter M., Hoeschen Ch., Thirolf P., Assmann W., Habs D., Prokofiev A., Ekström C., Hänsch T. W., and Holzwarth R., Radiation Induced Absorption in Rare Earth Doped Optical Fibers, IEEE Transactions on nuclear science 59, 425-433 (2012). [2] Spühler G. J., Krainer L., Innerhofer E., Paschotta R., Weingarten K. J., and Keller U., Soliton mode-locked Er:Yb:glass laser, Opt. Lett. 30, 263-265 (2005). [3] Paschotta R., Noise of mode-locked lasers. Part II: Timing jitter and other fluctuations, Appl. Phys. B 79, 163173 (2004). [4] Meyer S., Fortier T. M., Lecomte S., Diddams S. A., A frequency-stabilized Yb :KYW femtosecond laser frequency comb and its application to low-phase noise microwave generation, to appear in Appl. Phys. B. 19 Spacecraft Clocks and General Relativity R. Angélil, P. Saha Institute for Theoretical Physics, University of Zurich Winterthurerstrasse 190 8057 Zurich Switzerland [email protected] Abstract. Most discussion of relativity and STE-quest has focused on gravitational time dilation, which is the first relativistic correction, well-known from GPS satellites. But gravity has several more subtle effects on spacecraft clocks. Gravity affects not just time, but space also - modifying the clock's trajectory in curious ways. STEquest is a freely falling clock; and sending tick signals to be compared with another clock on Earth allows for the recovery of the clock's 4D worldline through space-time. If systematics can be sufficiently taken care of, STE-quest will manage to perform a plethora of tests of general relativity: All the classic tests, tests of higher-order gravitational time dilation, higher-order space curvature, frame-dragging, and possibly even the never-measured-before spin-squared effects. STE-quest timing is sensitive to GR perturbations in two ways - firstly through influences acting on the spacecraft's orbit itself, and secondly by curving the tick-signals as they travel from the satellite, through the Earth's gravitational field, to the waiting observer-clock on the Earth. We have performed numerical calculations which add relativistic perturbations to the orbit trajectory, as well as to the tick-signal trajectories. The satellite falls freely around the Earth on a relativistic orbit. The onboard clock 'ticks' in equal intervals of proper time, and broadcasts the fact, sending them on trajectories to the observer, who has a second clock. This clock is used to record the times-of-arrival of the remote clock's ticks. FIGURE 1. A clock orbits (black line) the Earth on an eccentric relativistic orbit. As it orbits, it sends ticks to a second clock located on the Earth (blue marker). These tick signals propagate on relativistic trajectories (not shown) to the Earth-based clock. To calculate the timing shift due to each effect, whether on the orbit or on the signal paths, we calculate the rate at which the clocks disagree first with the effect present, and then without. The difference is the redshift signal due to this effect. This abstract explores seven effects. Four are effects on the orbit, and three on signal paths. 20 Leading-order gravitational time dilation: One of the earliest predictions of General Relativity, a consequence of the Einstein Equivalence Principle, and routinely taken into account by GPS satellites. This has been well-tested. It affects the orbit only, not the signals. Space curvature: This is the first correction which bends space beyond the classical. Orbits are no longer conic sections, they precess. This has been observed on Mercury's orbit around the Sun, and in binary pulsar systems. Tick-signal trajectories are now bent – the photons do not move in straight lines. The contribution to timing is sometimes referred to as the Shapiro delay. Both these effects are easily with STE-quest's range. Frame-dragging: Earth's angular momentum causes a 'dragging' of space and time around the Earth. This is a consequence from the Kerr metric. Not only does the orbit precess, but the clock itself experiences a time dilation. It has been measured around the Earth by Gravity Probe B. It affects the orbit well as signals. Still within STE-quest's design capabilities. Spin-squared effects: Another set of predictions from the Kerr metric; a multitude of various effects enter the game here, all proportional to the square of the Earth's spin parameter. Orbits and signals have counterintuitive trajectories. This has never been tested before. They are within STE-quest's range in optimistic scenarios. FIGURE 2. Redshift (or derivative of time delay) signals from a variety of GR effects. The satellite has been allowed to orbit the Earth three times. The redshift residuals in the left column are due to the presence of a specific type of space-time curvature acting on the orbit, while those in the right column are the same curvature, yet acting on the tick signal propagation paths. 21 Given the amplitudes of some of these effects on the redshift (figure 2), if STE-quest aims to achieve a one-part-in-a-million recovery of the leading-order gravitational time dilation signal (first plot in figure 2), other relativistic perturbations cannot be ignored. Fortuitously, this means all of the alreadyperformed geodesic tests of general relativity, as well as a few more, may be possible with the STEquest experiment, provided the systematics can be handled. ACKNOWLEDGMENTS R.A. is supported by the Swiss National Science Foundation. 22 PHARAO: A Cold Cesium Clock for Space Applications P. Laurent1, M. Abgrall1, I. Morici1, P. Lemonde1, G. Santarelli1, A. Clairon1, S. Bize1, D. Rovera1, J. Guena1, C. Salomon2, F. Picard3, O. Grosjean3, C. Delaroche3, J-F. Vega3, B. Leger3, M. Saccoccio3, I. Zenone3, B. Faure3, C. Sirmain3, D. Massonnet3, S. Leon3, S. Beraud3, F. Buffe3, P. Lariviere3, C. Escandes3, N. Ladiette3, B. Vivian3, D. Blonde3, M. Chaubet3, C. Luitot3, P. Chatard4,C.M. De Graeve4, C. Maces5, S. Thomin5, J.P. Lelay5, T. Potier6, Y. Cossart6, T. Nauleau7, A. Granget8 LNE-SYRTE, 61 av. de l’Observatoire, 75014 PARIS, France. Laboratoire Kastler-Brossel, CNRS, 24 rue Lhomond, 75231 PARIS, France. CNES, 18 avenue Edouard Belin, 31401 TOULOUSE cedex, France Sogeti, 57 avenue du G. Decrouttes , 31100 Toulouse, France. Sodern, 20 Avenue Descartes,B.P. 23, 94451 LIMEIL-BREVANNES Cedex, France. THALES, 2 avenue Gay-Lussac, 78851 ELANCOURT cedex, France CS SI, ZAC de la Plaine – Rue Brindejonc des Moulinais, – BP 5872, 31506 TOULOUSE cedex 5, France EREMS, Chemin de la Madeleine, ZI, 31130 FLOURENS, France. Abstract. SYRTE and CNES are developing a primary frequency standard, called PHARAO, which is specially designed for space applications. The clock signal is referenced on the frequency measurement of the hyperfine transition performed on a cloud of cold cesium atoms (~1µK). The transition is induced by an external field feeding a Ramsey cavity. In microgravity the interaction time inside the cavity can be adjusted over two orders of magnitude by changing the atomic velocity in order to study the ultimate performances of the clock. An engineering model has been assembled to validate the architecture of the clock. This model has been fully tested on ground for operation faults. Of course the clock performances are reduced by the effect of the gravity on the moving atoms. The main results are a frequency stability of 3.3x10-13t-1/2. The main systematic effects have been analyzed and their frequency uncertainties contributions is 1.3x10-15. The clock has been compared with the PFS mobile fountain of SYRTE. The mean frequency shift is lower than 2.10-15. The mechanical and thermal space qualifications have been carried out by testing a representative mechanical model of the clock and by using refined calculations. The design of the clock has been improved and now the flight model is being assembled. The PHARAO clock is a key instrument of the European ESA space mission called ACES. This mission is dedicated to perform space-time measurements and test some fundamental physics aspects. The expected performances of PHARAO will be 10-13t-1/2 in frequency stability and lower than 3x10-16 in frequency accuracy. 23 Testing Chameleon Scalar Fields With STE-QUEST A. Schärer1, R. Bondarescu1, P. Jetzer1, A.P. Lundgren2 1 Institute for Theoretical Physics, University of Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland 2 Albert Einstein Institut, Callinstr. 38, 30167 Hannover, Germany [email protected] Abstract. STE-QUEST provides a unique possibility to constrain chameleon scalar field models where the coupling to matter depends on the surrounding matter density. In dense environments such as on the surface of the Earth the effective mass of the scalar particle becomes very large, suppressing the fifth force mediated by the field. In space, the small background density allows a positive detection of such a fifth force at a level that already has been excluded by experiments on Earth. If the scalar field couples differently to different species of matter, this causes a violation of the universality of free fall. In this poster, we show how STE-QUEST can constrain chameleon models which couple differently to the two Rb isotopes used in the atom interferometer on-board the satellite. Additionally, the presence of such a scalar field causes the gravitational red shift to deviate from the one expected in general relativity. Therefore the accurate tracking of the satellite on its elliptical orbit together with the atomic clock can further constrain chameleon models. 24 Tests of Lorentz Symmetry with STE-QUEST Jay D. Tasson1, Brett Altschul2, Quentin G. Bailey3 1 2 Physics and Astronomy Department, Carleton College, Northfield, MN 55057 Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208 3 Physics Department, Embry-Riddle Aeronautical University, Prescott, AZ 86301 [email protected] Abstract. The experimental investigation of Lorentz and CPT symmetries could provide a window into previously unprobed interactions—perhaps related to quantum gravitational effects at the Planck scale. The general effective field theory that incorporates Lorentz and CPT violation is the Standard-Model Extension (SME). Hence the SME provides a theoretical framework for analyzing and reporting results of experiments having the ability to test Lorentz and CPT symmetry. The STE-QUEST mission transports sensitive experiments among a wide range of Lorentz frames providing an extremely advantageous platform for testing Lorentz and CPT symmetries. This talk will provide an overview of the SME and a summary of the Lorentz-Symmetry tests that could be performed by the STE-QUEST mission. Clock experiments performed by the mission would result in sensitivities to up to 25 coefficients in the proton sector, with sensitivity levels ranging from 10−21 down to 10−28. A further 18 electron-sector coefficients may be constrained by these tests with potentially 10−19 to 10−27 level sensitivities. Lorentz violation also results in effective Weak Equivalence Principle (WEP) violation with a signature qualitatively different from other sources of WEP violation. The WEP tests planed for STE-QUEST would provide sensitivities to an additional 8 combinations of coefficients for Lorentz violation reaching levels ranging from 10−11 to 10−14. For most of these coefficients, these are unprecedented levels of sensitivity. 25 Quantum Mechanics at the Interface with Gravity Wolfgang P. Schleich Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, D-89069 Ulm, Germany [email protected] Abstract. Waves are uniquely suited to probe gravity. Tests of this kind not only include electromagnetic waves but also matter waves. We start our talk by briefly reviewing early proposals to test metric gravity using ringlaser gyroscopes. These ideas were later extended by employing matter wave interferometers such as the Kasevich-Chu (KC) interferometer. We provide a representation-free description of the KC interferometer and show that the phase shift is a consequence of the acceleration of the atom relative to the acceleration of the laser phases. The proper time difference between the two paths in the KC interferometer vanishes. This observation is in contrast to the Colella-OverhauserWerner neutron interferometer where the total phase shift is a consequence of a non-vanishing proper time difference. In this context the recent proposal by Zych et al. is interesting since it proposes an operational way to measure proper time differences by clocks. We briefly discuss these ideas. ACKNOWLEDGMENTS As part of the QUANTUS collaboration, this project is supported by the German Space Agency DLR with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant no. DLR 50WM0837. REFERENCES Schleich W., and Scully, M.O., “General Relativity and Modern Optics” in: New Trends in Atomic Physics, Proceedings of the Les Houches Summer School, Session XXXVIII, 1982, Eds.: R. Stora and G. Grynberg, North Holland, Amsterdam, 1984, p. 995-1124 Schleich, W.P., Greenberger, D.M., and Rasel, E.M., “The redshift controversy in atom interferometry: Representation dependence of the origin of phase shift”, Phys. Rev. Lett. 110, 010401 (2013) Schleich, W.P., Greenberger, D.M., and Rasel, E.M, “A representation-free description of the Kasevich-Chu interferometer: a resolution of the redshift controversy”, New J. Phys. 15, 013007 (2013) Greenberger, D.M., Schleich, W.P., and Rasel, E.M., “Relativistic effects in atom and neutron interferometry and the differences between them”, Phys. Rev. A 86, 063622 (2012) Zych, M., Costa, F., Pikovski I., and Brukner, C., “Quantum Interferometric visibility as a witness of general relativistic proper time”, Nature Communications 2:505, doi:10.1038/ncomms1498 (2011) 26 On the Potential of STE-QUEST Clocks for Relativistic Geodesy R. Bondarescu1, M. Bondarescu2, G. Hetenyi3, L. Boschi3, P. Jetzer1, J. Balakrishna4 1 Institute for Theoretical Physics, University of Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland 2 Universitatea de Vest, Vasile Parvan 4 Blvd, Timisoara, Romania 3 ETH Zurich, Sonneggstr. 5, 8092, Zurich, Switzerland 4 Harris-Stowe State University, St. Louis, MO 63103, USA [email protected] Abstract. Portable atomic clocks such as the ones built for STE-QUEST open many new possibilities in relativistic geodesy. They provide local, direct measurements of changes in the geopotential that can be used to determine the small-scale structure of the geoid (the geoid is the equipotential surface of the Earth that approximates the mean sea level and accounts for all subsurface density variations). Satellite missions carry out distance measurements at the location of the satellite and map the geoid over the entire globe. However, they require calibration and extensive computations including integration of derivatives of the potential, which is a non-unique operation. Additionally, these maps have low spatial resolution with the distance between the satellite and Earth being an important limiting factor. Local geoid measurements may be used to calibrate satellite maps and add detail to these maps in desired regions. Clocks have different depth sensitivity than gravimeters and may be combined with gravimetric surveying and/or other existent geophysical methods to provide a better understanding of the local substructure of the Earth. Clocks that measure a frequency change ∆f/f ~ 10-18 would be sensitive to geoid perturbations caused by a buried sphere of radius of ~1 km with 20% density anomaly (Bondarescu et al. 2012). Many areas in geophysics may benefit from such measurements including volcanology and seismology. In particular, I will describe the potential use of clocks for improving our understanding of volcanoes (Bondarescu et al. 2013; in preparation). REFERENCES Bondarescu, R. et al. 2012, Geophysical Applicability of Atomic Clocks: Direct Continental Geoid Mapping, Express Letter, Geophysical Journal International 191 pp. 78-82. Bondarescu, R et al. 2013, On the Applicability of Atomic Clocks to Volcanology, In Preparation. 27 Chip-based BEC Interferometry in Microgravity N. Gaaloul, W. Ertmer and E. M. Rasel, for the QUANTUS team QUEST, Institute of Quantum Optics - Leibniz University, Hanover, Germany [email protected] Abstract. A central goal of modern physics is to test fundamental principles of nature with ever increasing precision. Atomic quantum sensors are a key-technology for the ultra-precise monitoring of accelerations and rotations. These sensors evolved to a new kind of optics based on matter waves rather than light waves. Matter wave optics is still a young, but rapidly progressing science which recently generated sensational Nobel-prize awarded inventions. It allows for example to compare the free fall of two atomic clouds of different species, thus testing the weak equivalence principle in the quantum domain. In a weightless environment the precision of such sensors can be considerably increased by increasing the free propagation time of the atoms in the interferometer. In this poster, we present three projects where atom interferometers are realized in compact and autonomous apparatus suited to operate in µ-gravity environments. At the heart of the three experiments, atom chips are the key ingredient that allows for an unprecedented miniaturization of BEC machines. Atom chips have proven to be excellent sources for the fast production of ultra-cold gases due to their outstanding performance in fast evaporative cooling. The first generation of experiments consists in a Bragg-type interferometer on a chip operated with 87 Rb atoms in the thermal or Bose-Einstein condensed regime [1]. With the help of delta-kick cooling [2,3], implemented via the atom chip, we can further slow the expansion of the atoms down. With this toolbox we could extend the observation of a BEC of only 104 atoms up to two seconds. Benefiting from the extended free fall in the ZARM drop-tower in Bremen, we could operate an asymmetric Mach-Zehnder interferometer over hundreds of milliseconds (over 700 ms) to study the coherence and to analyze the delta-kick cooling with the help of the observed interference fringes [4]. A novel generation of atom chips allows improving the performance of these flexible devices. We have developed a novel loading scheme that allowed us to produce Bose-Einstein condensates of a few 105 87 Rb atoms every two seconds. The apparatus is also designed to be operated in microgravity at the drop tower in Bremen, where even higher numbers of atoms can be achieved in the absence of any gravitational sag. Using the drop tower’s catapult mode, our setup will perform atom interferometry during nine seconds in free fall. Thus, the fast loading scheme allows for interferometer sequences of up to seven seconds – interrogation times which are inaccessible for ground based devices. Moreover, differential interferometry will be performed on the same device with the additional production of a Potassium quantum degenerate source. As a next step towards the transfer of such a system in space, either on board the ISS or as a dedicated satellite mission, a chip-based atom interferometer operating on a sounding rocket is currently being built. The success of this project would mark a major advancement towards a precise measurement of the equivalence principle with a space-born atom interferometer. ACKNOWLEDGMENTS The QUANTUS cooperation comprises the group of C. Lämmerzahl (Univ. Bremen), A. Wicht (FBH) A. Peters (Humboldt Univ. Berlin), T. Hänsch/J.Reichel (MPQ/ENS), K. Sengstock (Univ. Hamburg), R. Walser (TU Darmstadt), and W.P. Schleich (Univ. Ulm). This project is supported by the German Space Agency Deutsches Zentrum für Luft- und Raumfahrt (DLR) with funds provided by the Federal Ministry of Economics and Technology (BMWI) under grant number DLR 50 WM 0346. We thank the German Research Foundation for funding the Cluster of Excellence QUEST Centre for Quantum Engineering and Space-Time Research. REFERENCES [1] T. van Zoest et al., Science 328, 1540 (2010). 28 [2] S. Chu, J. E. Bjorkholm, A. Ashkin, J. P. Gordon, and L.W. Hollberg, Opt. Lett. 11, 73 (1986). [3] H. Amman and N. Christensen, Phys. Rev. Lett. 78, 2088 (1997). [4] H. Müntinga et al., Phys. Rev. Lett. 110, 093602 (2013). 29 Introduction of Time and Frequency Package for China Space Station Project S. Zhang1, T. Liu1, L. Liu2, J. Chen1 1 2 National Time Service Center, Chinese Academy of Sciences, Xi'an 710600, P.R. China Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, P.R. China Abstract. As planed the china’s manned space station will be launched in 2020. The scientific research platform can support versatile science and technology experiment in low gravity environment. As an essential part of fundamental scientific research, time and frequency package will be devoted to develop new technology for space application and provide service for space and ground users. The main scientific objects include international comparison of atomic clocks, verification of relativity, mapping of the absolute gravitation equipotential surface and so on. The time and frequency package is composed of two main parts, the atomic clock assemble and the time and frequency transfer link. The atomic clock assemble include a Hydrogen maser, a Cs atomic beam clock and a Sr lattice clock. The Hydrogen maser and the Cs atomic beam clock will be launched in the early phase to provide a good-for-use frequency standard to fulfill the parts requirement of some application. Aiming at the highest precision people could achieve, the optical clock will be launched mostly in the later launching opportunity. Presently a microwave frequency link and a laser time link are included to provide the space-ground time and frequency link. The time and frequency package is assumed to be able to produce a high-precision time and frequency signal with a short-term stability better than 2×10-15/s, and accuracy better than 1×10-17. And the time and frequency signal can be transferred between the space station and the ground stations with a fidelity of 0.3ps@300s and 6ps@1day. Presently more than ten research groups in the field of time and frequency in China are involved in this huge research and engineering project. National time service center (NTSC) is the chairman research unit and responsible for coordinating. NTSC is a national research institute assuming the tasks of national standard time generating, keeping and transmitting. Presently NTSC is devoted in the development of high-precision atomic clocks and time and frequency transfer technique, including Cs fountain clocks, Sr lattice clocks, Two-Way Satellite Time and Frequency Transfer, fiber time and frequency transfer and quantum time transfer. 30 Atom Interferometry for Inertial Sensing and Fundamental Physics at the IQO J.Hartwig1, D.Schlippert1, H.Albers1, J.Matthias1, S.Abend1, G.Tackmann1, P.Berg1, C.Schubert1, E.M.Rasel1, W.Ertmer1 1 Institute for Quantum Optics- Leibniz University of Hannover [email protected] Abstract. The use of devices based on atom interferometry as inertial sensors and tools of fundamental physics is a fast progressing field of study. In the Institute for Quantum Optics in Hannover we operate two dedicated lab based experiments in the most common configurations as an atomic gyroscope and gravimeter respectively. Both experiments are in their own right of scientific interest, but also lay the foundation for our efforts in pushing the technology into more critical environments. Based on the operational experience and systematic analyses of this experiments miniaturized and fully mobile sensors are in the progress of implementation to operate in the Drop Tower of Bremen, Sounding Rocket Missions and as tools for geodesy. Similar to the STE-QUEST equivalence principle measurement scheme the presented atomic gravimeter can be operated simultaneously with two different atomic species. In this lab based experiment we aim for a comparison of the gravitational acceleration of 39K and 87Rb in the near future. In principle this choice of species can be adjusted to compare all of the potassium and rubidium isotopes. The flexibility of the experimental setup allows for a systematic study of experimental and physical constraints on core issues of such a differential measurement. Up to date the rubidium gravimeter is fully operational and was used to analyze the expected performance of a comparison measurement. During a 42h measurement campaign a vibrational noise limited sensitivity of about 3.9*10-8 m/s2 with 4.9*104 s integration time was demonstrated. Based on this result an analysis of the expected noise sources in the differential measurement leads to an inferred sensitivity of 4.3*10-8 g/Hz1/2. We will report on the progress in implementing the second species. The second experiment presented is an atomic gyroscope measuring earth rotation by simultaneous measurement of two contrapropagating 87Rb clouds. The summed signal is proportional to the rotationrate while accelerations, vibrations and offsets are suppressed. Similar to a gravity gradiometer this is an example for a differential measurement of two atom interferometers with the same atomic species differentiated by external degrees of freedom. In contrast to a gradiometric measurement in this case both atomic clouds pass through the exactly same environment just separated by time. The resulting techniques developed in the scope of this experiment to compensate for differential effects are of great interest for future atom interferometric sensors employing co-located clouds. The lab based experiment was able to demonstrate sensitivity to rotations at the level of 20 nrad/s after 5000 s of Integration. We will report on the performance of the sensor and used mitigation techniques for spurious rotational noise. ACKNOWLEDGMENTS The work of J.Hartwig is supported by the German Space Agency Deutsches Zentrum für Luft- und Raumfahrt (DLR). REFERENCES M.Zaiser, J.Hartwig, D.Schlippert, U.Velte, N.Winter,V.Lebedev,W.Ertmer and E.M.Rasel “Simple method for generating Bose-Einsetein condensates in a weak hybrid trap” Phys.Rev.A. 83 , 035601(2011). T.Müller, M.Gilowski, M.Zaiser, P.Berg, Ch.Schubert, T.Wendrich, W.Ertmer and E.M.Rasel., “A compact dual atom interferometer gyroscope based on laser cooled rubidium” Eur.Phys.J.D.53, 273-281(2009). G.Tackmann, P..Berg, Ch.Schubert, S.Abend, M.Gilowski, W.Ertmer and E.M.Rasel., “Self-alignment of a compact large-area atomic Sagnac Interferometer” New J.Phys. 14 , 015002(2012). 31 STE-QUEST Differential Atom Interferometer E. M. Rasel, for the STE-QUEST consortium QUEST, Institute of Quantum Optics - Leibniz University, Hanover, Germany [email protected] Abstract. STE-QUEST ATI aims for a test of General Relativity through testing the Universality of Free Fall with a dual species atom interferometer on a satellite. This test is based on measuring the differential acceleration of two test bodies assumed to be zero by Einstein's Equivalence Principle (EP). The Eötvös ratio derived from the differential signal will be determined with an accuracy of parts in 1015 beyond state-of-the-art precision of 10-13 established by Lunar laser ranging and torsion balances. Quantum degenerate ensembles of 87Rb and 85Rb will act as test bodies in the dual species interferometer testing the EP in the Quantum domain. Thanks to the weightlessness conditions in space these test masses will be simultaneously prepared and interrogated with a free evolution time of 10 s. Within a single cycle of 20 s a shot-noise limited sensitivity to accelerations of 3 10-12 m/s2 is anticipated. The simultaneous interferometry is carried out in double diffraction Mach-Zehnder geometry. Challenges in this mission lie both in suppressing noise and bias terms as well as in the accommodation to the limited resources of a satellite. In the talk the measurement principle will presented, an overview of the preliminary payload design will be given, and the estimated error budget will be discussed. ACKNOWLEDGMENTS The STE-QUEST consortium consists of leading European groups in the field of Atom Interferometery and space sciences. This instrument team was founded to respond to the proposal for an M3 mission in the frame of the Cosmic Vision program of ESA. This assessment phase is supported by the German Space Agency Deutsches Zentrum für Luft- und Raumfahrt (DLR). 32 Grating Chips for Quantum Technologies C. C. Nshii1, M. Vangeleyn1, J. P. Cotter2, P. F. Griffin1, E. A. Hinds2, C. N. Ironside3, P. See4, A. G. Sinclair4, E. Riis1 and A. S. Arnold1* 1 Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK 2 Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Rd, London SW7 2BW, UK 3 Rankine Building, School of Engineering, University of Glasgow, Glasgow G12 8LT, UK 4 National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK *[email protected] Abstract. We have developed and demonstrated [1] a microfabricated chip based on planar, diffractive optics, that enables a single beam of light impinging on it to produce all the light beams required to form a magneto-optic trap (MOT). This simplifies the integration of laser cooling into compact and ultimately portable devices. In such a MOT, with a 1cm3 beam overlap volume, we have trapped up to 6×107 87Rb atoms - comparable to the population of a conventional MOT with the same trapping volume. By contrast, the largest microfabricated pyramid MOT [2] has a much smaller trapping volume and hence four orders of magnitude fewer atoms. The planar diffractive gratings are manufactured as quarter-wavelength deep grooves (1D gratings) or indentations (2D gratings) etched in a semiconductor surface and coated with gold or aluminium. Figure 1 shows an example with three 1D gratings arranged in a triangle to produce a tetrahedral configuration of beams, i.e. to form a 4beam MOT [3]. The grating period is chosen to produce only first-order diffracted beams. With a circularly polarised input beam the purity of the polarisation in the diffracted orders is surprisingly high (>96%) and with the correct orientation, which enables the formation of the MOT with no additional optics. The grating shown in Figure 1 has a slightly smaller overlap volume than some of your 2D geometries and consequently traps a maximum of 1.8×107 87 Rb atoms. However, by adjusting the reflectivity of the coating applied to this grating it is possible to match the upward force from the diffracted beams to that of the incoming beam. This has allowed the realisation of balanced optical molasses and the observation of sub-Doppler temperatures (50 μK). FIGURE 1. Fig. 1. Scanning electron microscope image of a triangular grating consisting of three 1D gratings, each with a period of 1400 nm (diffraction angle 34° relative to normal at 780 nm). This produces a tetrahedral set of MOT beams from a single input beam. As all reflected beams are generated by the same diffractive optical element there is a fixed phase relationship between them at any given point and hence together with the input beam they will form a phase-stable optical lattice. The performance and simplicity of this setup combined with good optical access for probing and observation makes this a promising technology for portable measurement devices such as atomic clocks and magnetometers. 33 REFERENCES 1 C.C. Nshii, M. Vangeleyn, J.P. Cotter, P.F. Griffin, E.A. Hinds, C.N. Ironside, P. See, A.G. Sinclair, E. Riis and - See for A.S. Arnold, Nature Nanotechnology (2013) http://dx.doi.org/10.1038/NNANO.2013.47 Acknowledgments 2 S. Pollock, J.P. Cotter, A. Laliotis, & E.A. Hinds, Opt. Express 17, 14109 (2009); S. Pollock, J.P. Cotter, A. Laliotis, F. Ramirez-Martinez, & E. A. Hinds, New J. Phys. 13, 043029 (2011). 3 M. Vangeleyn, P.F. Griffin, E. Riis & A.S. Arnold, Opt. Express 17, 13601 (2009); M. Vangeleyn, P.F. Griffin, E. Riis & A.S. Arnold, Opt. Lett. 35, 3453 (2010). 34 Compact Semiconductor Laser Modules Designed for Precision Quantum Optical Experiments in Space Ahmad Bawamia1*, Max Schiemangk1,2, Anja Kohfeldt1, Erdenetsetseg Luvsandamdin1, Christian Kuerbis1, Alexander Sahm1, Andreas Wicht1, Goetz Erbert1, Achim Peters1,2, and Guenther Tränkle1 1. Ferdinand-Braun Institut, Leibniz Institut fuer Hoechstfrequenztechnik, Berlin, Germany 2. Humboldt-Universitaet zu Berlin, Germany * [email protected] Abstract. We review the major technological considerations related to the development of high power, narrow-linewidth, hybrid diode laser systems for quantum optics experiments in space. We concentrate on GaAs-based laser chips engineered for emission at 780 nm, which meet the electrooptical requirements set forth by the STE-QUEST mission proposal. We discuss different chip concepts that are available, i.e. distributed feedback lasers, ridge waveguide amplifiers, tapered amplifiers, and phase modulator chips and we assess the TRL of the GaAs laser chip technology. We discuss different laser module concepts (master oscillator power amplifier module concept, low power local oscillator module, high power dual stage amplifier module) and compare them w.r.t. electro-optical performance, power and mass budget, and form factor. We use a micro-integration approach to integrate the laser chips together with beam forming optics and the electrical interface into a compact and robust laser module. The micro-integration technology is described and its space adequacy and TRL are assessed. The laser concepts as well as the chip and micro-integration technology suggested for STE-QUEST are currently being used in BEC experiments carried out at the ZARM drop tower and will be tested in space during sounding rocket missions that are scheduled for 2013 and 2014 within the framework of projects funded by the German Space Agency DLR. ACKNOWLEDGMENTS This work is supported by the German Space Agency DLR with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant numbers 50WM0940, 50WM1134 and 50WM1141. 35 STE-QUEST Mission: Atom Interferometer Performance Assessment And Error Estimations C. Schubert1 for the STE-QUEST ATI team 1 Institute for Quantum Optics- Leibniz University of Hanover [email protected] Abstract. The STE-QUEST ATI aims for performing a quantum test of Einstein’s Equivalence principle by probing the universality of the free propagation of matter waves on a satellite. A dual species atom interferometer will measure the differential acceleration of Bose-Einstein condensates of 87 Rb and 85Rb assumed to be zero if the inertial mass coincides with the gravitational mass. The Eötvös ratio for two species A and B can be rewritten for a space borne environment as η(A,B)=|aA-aB|/g with aA and aB being the acceleration of the respective species and g the local gravitational acceleration. This ratio derived from the differential signal Δa=a87-a85 shall be determined with an accuracy of parts in 1015 beyond state-of-the-art precision of 10−13 established by lunar laser ranging and torsion balances. The choice of 87Rb and 85Rb as test bodies will allow for a high common-mode suppression ratio and the low velocity spread inherent to the BECs will preserve the interferometer contrast. A single measurement cycle consists of a simultaneous generation of the two BECs of 106 atoms lasting 10 s and followed by the propagation in the interferometer. During the latter phase, both isotopes will be simultaneously interrogated by a double diffraction pulse sequence π/2 – π – π/2 with a free evolution time of T = 5 s between two consecutive pulses. Subsequently, both atom interferometer signals will be read-out leading to a total cycle time of 20 s. These long evolution times for atoms in free fall are solely possible in a space-borne environment and go beyond earth-based zero g simulators. Anticipating the shot-noise limit, the sensitivity to differential accelerations per cycle will be 3·10−12 m/s2. During the 5-year mission duration the target sensitivity will be reached by integration. The STEQUEST ATI will operate in science mode during the perigee pass of the highly elliptical orbit, where the local gravitational acceleration is above 3 m/s2, yielding a sensitivity to the Eötvös ratio of ~5·10−14 per orbit. The atom source is required to produce a mixture of 87Rb and 85Rb BECs of 106 atoms each and an effective temperature of 70 pK in less than 10 s. The condensation is reached in a 40 Hz optical dipole trap while the interactions are tuned with an external magnetic field (168 G) around the Feshbach resonance of 85Rb. This leads to 106 atoms of each isotope with an effective temperature of 1 nK. After a short expansion time, a delta-kick cooling pulse is further applied lowering the effective temperature to the anticipated 70 pK. This temperature is motivated by the velocity selectivity of the beam splitting process and velocity dependent phase shifts which could cause a dephasing over the atomic ensemble and consequently a reduction of the interferometer contrast. The kick parameters also allow tuning of the differential expansion rates between the two isotopes. It is targeted to lock the expansion rates at a level of 0.1% which relaxes significantly the requirements on the differential wave-front curvature of the beam splitter lasers. Using 87Rb and 85Rb as test bodies enables matching the scaling factors and the pulse timings of both atom interferometers. With an effective wave-vector matching of 10-9, a Rabi frequency match of 10-4, and switching the beam splitter light field for both isotopes at exactly the same time, the expected common-mode suppression ratio for spurious accelerations of the spacecraft, certain bias terms related to gravity gradients, and spurious rotations is 2.5·10−9. Remaining bias terms linked to gravity gradients and spurious rotations depend on the spatial overlap and the differential velocity of the two isotopes. Constraints on the distance are on the nm level, while the velocity requirements are on a level of 0.3 nm/s. A bias to the second order Zeeman shift will be mitigated for by alternating the interferometer input states for subsequent cycles. Contributions of remaining mean field energy are expected to be far below the target accuracy. Additional gravity gradients arising from the payload are under investigation. 36 In the poster the measurement principle will be presented, an overview of the simultaneous generation of the two BECs will be given, and the estimated error budget will be discussed. ACKNOWLEDGMENTS This assessment phase is supported by the German Space Agency – Deutsches Zentrum für Luft- und Raumfahrt (DLR). REFERENCES ESA STE-QUEST mission homepage: http://sci.esa.int/ste-quest Wagner, T.A., and Schlamminger, S., and Gundlach, J.H., and Adelberger, E.G., “Torsion-balance tests of the weak equivalence principle,” Class. Quantum Grav. 29, 184002 (2012) Müller, J., and Hofmann, F., and Biskupek, L., “Testing various facets of the equivalence principle using lunar laser ranging,” Class. Quantum Grav. 29, 184006 (2012) Williams, J.G., and Turyshev, S.G., and Boggs, D.H., “Lunar laser ranging tests of the equivalence principle,” Class. Quantum Grav. 29, 184004 (2012) Lévèque, T., and Gauguet, A., and Michaud, F., and Pereira Dos Santos, F., and Landragin, A., “Enhancing the Area of a Raman Atom Interferometer Using a Versatile Double-Diffraction Technique,” Phys. Rev. Lett. 103, 080405 (2009) van Zoest, T., et al., “Bose-Einstein Condensation in Microgravity,” Science 328, 1540 (2010) Müntinga, H., et al., “Interferometry with Bose-Einstein Condensates in Microgravity,” Phys. Rev. Lett. 110, 093602 (2013) 37 The Yb Lattice Clock (and others!) at NIST for Space-Based Applications C. Oates, J. Sherman, N. Hinkley, N. Phillips, M. Schioppo, R. Fox, K. Beloy, J. Olson, and A. Ludlow Time and Frequency Division National Institute of Standards and Technology 325 Broadway Boulder, Colorado, USA 80303 [email protected] Abstract. As part of our continuing efforts to realize the SI second to its fullest extent, the Time and Frequency Division at the National Institute of Standards and Technology in Boulder, Colorado has a variety of ongoing research activities to support development of timing technology for the present and future. Of particular relevance to proposed space-based projects are the NIST microwave time scale (ultimately anchored by two Cs fountain clocks) and the optical atomic clock program, which consists of research in both ion and neutral atom clocks. These optical clocks are part of a world-wide effort to develop revolutionary new timing systems with unprecedented stability and accuracy. I will survey the efforts on this research with emphasis on new results with the Yb optical lattice clock, which has recently demonstrated extremely low levels of frequency instability. The microwave and optical clocks will be connected to space experiments (e.g., to the International Space Station) through a microwave link (and perhaps one day also through an optical link) to a Ground Station presently under construction. This link is in support of the ACES Project as part of a NASA/ESA collaboration. A platform that is compatible with existing ESA microwave link hardware is well under way here at NIST, and we anticipate installation of the ESA hardware in 2014. The various optical clocks at NIST (including the state-of-the-art Sr lattice clock in Jun Ye’s Group at JILA) are connected to each other and to the microwave clocks here by means of fs-laser frequency combs, which have demonstrated 10-19 fractional frequency transfer fidelity. Such connections would also presumably serve well to make the necessary connections to space clocks via our space link hardware. NIST has two Cs fountain primary standards, F1 and F2, which are used to calibrate a microwave clock ensemble that together comprise the NIST Time Scale. The room temperature standard, F1, has an evaluated absolute fractional frequency uncertainty of 3 x 10-16, while the newer, cryogenic standard, F2, will officially come online soon with a still smaller uncertainty (due to a greatly reduced BBR shift). As for the optical clocks, NIST has two trapped ion clock systems, based on Hg+ and Al+ (two versions), which have demonstrated uncertainties of 1.8 x 10-17 and 8.9 x 10-18, respectively, the most accurate to date, and have been used to put stringent limits on present day drifts in fundamental constants and to demonstrate possibilities for relativistic geodesy. Additionally, NIST has neutral atom lattice clocks, based on Sr and Yb, which have demonstrated fractional frequency instabilities of ~ 3 x10-16 τ-1/2. These systems have been evaluated at the 10-16 uncertainty level, with good prospects to reach the low 10-17’s in the near future.Furthermore, due to the large number of atoms they employ, these systems have been able to demonstrate unprecedented levels of frequency stability. Finally, there is a compact Ca system based on a thermal atomic beam, which has good prospects for high stability (~10-15 @ 1 s) with a single laser system. Although it has limited capabilities for high accuracy, it could be well suited for experiments requiring high stability, and could be much more easily put in a transportable package than its more accurate counterparts. In addition to the Ca clock, in our neutral atom clock lab we have been focusing on the Yb lattice clock, which, along with the Sr lattice clock, is one of the two systems identified by the ESA Space Optical Clock (SOC) Program as prime candidates for future clocks-in-space programs. As part of a NASA Program in support of the SOC Program, we are pushing the Yb system to maturity for space science applications in three ways: (1) we are improving the accuracy of the Yb clock to meet the 10-17 accuracy specification required for the SOC, (2) we are putting together the minimum power/laser requirements for a Yb lattice clock, and (3) we are demonstrating a compact, robust, fiber-based fslaser frequency comb to connect the Yb clock laser light to other parts of the visible spectrum for possible free-space transmission. A key part of this effort has been to bring online a second Yb lattice 38 total Allan deviation clock system (Yb2), so we can make clock-clock comparisons to help optimize and verify clock performance. The two clocks each use several thousand Yb atoms that are confined in a 1-D fardetuned optical standing wave. We excite an extremely narrow transition at 578 nm in these atoms with highly pre-stabilized laser light, and use the resulting signals to fix the laser frequency on that of the atomic transition. Recently “Yb2” has become operational, and here we will report some of the first results from our Yb1-Yb2 clock comparisons. In Figure 1, we show the measured stability for the clocks. This plot highlights the advantages of optical clocks in general, which can be 1-2 orders of magnitude more stable than the best microwave clocks, and of lattice clocks in particular, which are able to reach precisions of 1 part in 1017 in less than 2000 seconds of averaging time. This level of stability has enormous implications not only for efficient evaluation of various systematics, but also for providing high precision timing signals for applications ranging from global positioning to tests of fundamental physics. 10-16 10-17 1 10 100 1000 averaging time (s) FIGURE 1. Allan Deviation for a single Yb optical lattice clock (red circles). The stability averages down with a slope of 4.5 x 10-16τ-1/2. Note that these data reflect a factor of √2 that has been divided from the Allan Deviation of the difference frequency signal between Yb1 and Yb2. ACKNOWLEDGMENTS The authors gratefully acknowledge support from NIST, the National Aeronautics and Space Agency’s ESA/NASA ACES Program, and the DARPA QuASAR Program. We also acknowledge tremendous assistance with the Yb work from Nathan Lemke and Yanyi Jiang, and with the fs-comb work led by Scott Diddams and co-workers. We thank our colleagues throughout the Division and at NIST (too numerous to list here) whose work on microwave and optical clocks will be included in the presentation. REFERENCES Fox, R. W., Sherman, J. A., Douglas, W., Olson, J. B., Ludlow, A. D., and Oates, C. W., “A High Stability Optical Frequency Reference Based On Thermal Calcium Atoms,” Proceedings of 2012 IEEE International Frequency Control Symposium, Baltimore, MD, May 21-24, 2012, pp. 404-406. Heavner, T. P., Parker, T. E., Shirley, J. H., Kunz, P., and Jefferts, S. R., “NIST F1 and F2,” Proceedings of 42nd Annual Precise Time and Time Interval (PTTI) Meeting, Reston, VA, Nov. 15-18, 2010, pp. 457-462. Lemke, N., Ludlow, A. D., Barber, Z., Fortier, T., Diddams, S. A., Jiang, Y., Jefferts, S. R., Heavner, T. P., Parker,T. E., and Oates, C. W., “A Spin-1/2 Optical Lattice Clock,” Phys. Rev. Letters 103, 063001 (2009). 39 Ma, L.-S., Bi, Z., Bartels, A., Robertsson, L., Zucco, M., Windeler, R. S., Wilpers, G., Oates, C. W., Hollberg, L., and Diddams, S. A., “Optical Frequency Synthesis and Comparison at the 10-19 Level,” Science 303, 1843 (2004). Nicholson, T. L., Martin, M. J., Williams, J. R., Bishof, M., Swallows, M. D., Campbell, S. L. and Ye, J., “Comparison of Two Independent Sr Optical Clocks with 1×10-17 Stability at 103 s,” Phys. Rev. Letters 109, 230801 (2012) Rosenband, T., Hume, D. B., Schmidt, P. O., Chou, C. W., Brusch, A. Lorini, L., Oskay, W. H., Drullinger, R. E., Fortier, T. M, Stalnaker, J. E., Diddams, S. D., Swann, W. C., Newbury, N. R., Itano, W. M., Wineland, D. J., and Bergquist, J. C., “Frequency Ratio of Al+ and Hg+ Single-Ion Optical Clocks; Metrology at the 17th Decimal Place,” Science 319, 1808-1812 (2008). 40 Tests of Irradiation Robustness of a Fabry–Pérot Resonator Comprising Highfinesse Fused Silica Mirrors and a ULE Spacer Q.-F. Chen1, A. Nevsky1, S. Schiller1, E. Portuondo Campa2, S. Lecomte2, O. Karger3, B. Hidding3, G. Pretzler3, D. Parker4, 5 Th. Legero , S. Häfner5, U. Sterr5 1 Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany 2 Centre Suisse d'Electronique et Microtechnique SA, 2002 Neuchâtel, Switzerland 3 Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany 4 School of Physics and Astronomy, University of Birmingham, B15 2TT Birmingham, United Kingdom 5 Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany E-Mail: [email protected] Abstract. In the STE-QUEST mission, an atomic clock will orbit in space on a highly elliptic orbit for a duration of up to 5 years. The ultra-stable microwave local oscillator for probing the atomic hyperfine transition of cold Cs atoms will be derived from an ultrastable laser via a femtosecond frequency comb. The ultra-stable laser will be obtained by locking a Nd:YAG laser optical frequency to a high-finesse optical cavity. The space particle radiation incident the spacecraft may influence and downgrade the cavity properties (e.g. its linewidth, in-coupling efficiency, and long-term length drift). Until now, there has been no reported research on the influence of radiation on the linewidth and the throughput of a high-finesse Fabry-Perot cavity, to the best of our knowledge. Previously, a low-finesse cavity has been spacequalified by the company TESAT and is used in their Nd:YAG space laser product [1]. In this work we studied the influence of electron and proton radiation on the linewidth and throughput of high-finesse cavities. We find no measurable degradation of the finesse of high-finesse (> 100 000) mirrors at the proton radiation levels of the STE-QUEST 5-year duration orbit behind 10 mm aluminum shielding. Moreover, the incoupling efficiency remains at a good level. Preliminary electron irradiation was also performed, using MeV electron generated in a laser plasma. Preliminary results are consistent with absence of strong degradation. To obtain the influence of ionizing radiation on the complete cavity, a small cavity made from ultralow expansion glass of length 20 mm and diameter 14 mm with optically contacted mirrors was constructed. A system was set up to determine the length, the frequency stability and the coefficient of thermal expansion of the cavity by observing its resonance frequency in comparison to an optical frequency standard. These measurements will be then be repeated after irradiation. ACKNOWLEDGMENTS The research leading to these results has received funding from the Bundesministerium für Wirtschaft und Technologie (Germany) under project no. 50OY1201. REFERENCES [1] Heine, F., Lange R., Schieber K., Windisch S., Smutny B., “Coherent Seed Laser for the AEOLUS Mission”, 14th Coherent Laser Radar Conference, Snowmass, CO, USA, 2007. 41 Development of a Robust Demonstrator for an Ultra-stable Optical Cavity for the STE-QUEST Mission Q.-F. Chen1, M. Cardace1, I. Ernsting1 A. Nevsky1, S. Schiller1, Th. Legero2, S. Häfner2, U. Sterr2 1 Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany 2 Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany E-Mail: [email protected] Abstract. For the STE-QUEST mission [1] an ultra-stable and ultra-low-noise microwave radiation is required to interrogate the Cs hyperfine transition at 9.2 GHz of the onboard Cs atomic clock. The relative frequency instability of the microwave is specified at lower than 3.5 x 10-15 for integration times between 1 and 100 s, after linear drift removal. The phase noise of the microwave radiation has to satisfy the following upper limits: PSD (dBrad2/Hz) -90 -110 -115 -120 -120 Frequency (Hz) 1 10 100 1000 10000 Table 1. Phase noise requirements for the microwave radiation The microwave radiation will be generated by stabilizing the frequency of a monolithic Nd:YAG laser at 1064 nm to an ultra-stable high-finesse cavity and then converting the laser frequency to the required microwave frequency by using a femtosecond frequency comb. This poster describes the development of a robust demonstrator of an ultrastable cavity for the STEQUEST mission within the ongoing MOLO project funded by DLR. The 10 cm long ULE cavity with fused silica mirrors and ULE compensation rings [2] possesses a finesse of 500 000 (Fig. 1 left) and is supported at 10 "magic" points in a semi-rigid frame in order to achieve a low vibration sensitivity and tolerate a rocket launch. The cavity and the frame are placed inside a compact aluminum vacuum chamber with the size of approx. 14 x 14 x 25 cm3 (Fig. 1 right). A compact and robust optical setup for laser frequency stabilization including home-made miniature motorized kinematic mirror mounts for beam alignment optimization into the cavity, and an acousto-optic modulator for laser power stabilization is assembled on a miniature breadboard and attached to the vacuum chamber. The laser radiation is led to the breadboard using a single-mode optical fiber. Fig. 1. Left – the MOLO cavity. Right – the vacuum chamber for the MOLO cavity with the attached compact optical setup for laser frequency stabilization 42 A Nd:YAG laser is stabilized to the cavity using the Pound-Drever-Hall technique. Two additional similar cavities, with increased length of 30 cm, will be used to characterize the frequency stability of the MOLO cavity by means of the "three-cornered-hat" method [3]. All cavities will be placed on active vibration isolation supports. A vibration test of the MOLO cavity setup is planned to be performed at ZARM, Bremen. The robustness of the MOLO system will also be tested in the temperature range of – 20 to +50°C. ACKNOWLEDGMENTS We thank D. Iwaschko and P. Dutkiewicz for electronics development and A. Uhde for providing the mechanical parts. The research leading to these results has received funding from the Bundesministerium für Wirtschaft und Technologie (Germany) under project no. 50OY1201. REFERENCES 1. STE-QUEST Mission http://sci.esa.int/ste-quest 2. T. Legero, T., Kessler, T. and Sterr, U., "Tuning the thermal expansion properties of optical reference cavities with fused silica mirrors," J. Opt. Soc. Am. B 27, 914 (2010). 3. A. Premoli and P. Tavella, "A revisited three-cornered hat method for estimating frequency standard instability", IEEE Trans. Instrum. Meas. 42, 7 (1993). 43 STE-QUEST Atom Interferometer (ATI) Payload Overview T. Schuldt1,2 for the STE-QUEST ATI team 1 DLR-Institute of Space Systems, 28359 Bremen, Germany 2 ZARM, University Bremen, 28359 Bremen, Germany [email protected] Abstract. The STE-QUEST Weak Equivalence Principle test is based on a differential measurement between two atom interferometers, operating with Rb85 and Rb87, respectively, where the accelerations of the two atom clouds under the influence of the Earth’s gravity field are compared simultaneously. As both atom interferometers are operated at the same time, also using the same optical components, a high common-mode rejection is achieved. The instrument design is based on the expertise of the consortium, which includes the DLR-funded cold atom experiments QUANTUS (QUANTengase Unter Schwerelosigkeit) and MAIUS (Materiewelleninterferometrie Unter Schwerelosigkeit), both operated in drop-tower experiments, and the CNES-funded experiment I.C.E. (Interférométrie Cohérente pour l'Espace) operated in zero-g parabola flights. For STE-QUEST, BoseEinstein- Condensates (BECs) are prepared on an atom chip, which is beneficial with respect to power, mass and dimensions. The atom interferometer is subdivided into three units Physics Package (PP), Laser System (LS) and Electronics. The physics package is subdivided into the atomic source, the science chamber (including detection unit), the vacuum pump system and the magnetic shielding. The coherent matter wave source consists of the dispensers (heated reservoir) and a 2D-MOT. The science chamber features a dodecagon design housing the three-layer atom chip. A 3D-MOT and an optical dipole trap (ODT) are implemented. The 3D-MOT uses two counter-propagating laser beams parallel to the atom chip and an additional laser beam reflected by the chip surface with an angle of 45°. The ODT uses two laser beams with an angle of 22.5° between them. The homogeneous magnetic fields for the experiment are created using three pairs of coils in Helmholtz configuration. The STE-QUEST atom interferometer will utilize a Raman double diffraction scheme with three laser pulses in π/2 – π – π/2 configuration. All laser beams – also for Rb85 and RB87 – are applied through the same optical fibers. The three laser pulses are separated by the free evolution time of 5 s. The first π/2 laser coherently splits the atomic ensemble, the second π-pulse redirects the movements of the atomic ensembles and the last π/2 pulse recombines the two ensembles. For detection, the atom interferometer will use the fluorescence signal from the atoms which are illuminated by a pair of counter-propagating laser beams of equal intensity. The fluorescence signal is imaged on a CCD. Absorption detection is additionally foreseen for sanity check and characterization. The vacuum pump system needs to establish a vacuum at the 10-11 mbar level. A combination of a passive getter pump and an ion getter pump is foreseen. As external magnetic stray fields need to be suppressed by a factor >10.000, a three layer mu-metal shielding is foreseen around the physics package. The magnetic shielding for STE-QUEST is based on the experience in the QUANTUS and MAIUS projects and needs to be capable to withstand internal fields up to 160 G without permanent damage. The magnetic field is monitored using specific magnetometers. The laser system consists of several subsystems with well-defined interfaces. The reference and the optical dipole trap laser are based on telecommunication components, i.e. fiber technology. The reference laser will operate at a wavelength of 1560 nm using a commercial ECDL (External Cavity Diode Laser) in combination with an EDFA (Erbium Doped Fiber Amplifier). Part of the 5 W output is frequency doubled using a PPLN (Periodically Poles Lithium Niobate) crystal, delivering the laser beams for the spectroscopy module. The main part of the EDFA output is used as input for the optical dipole trap, using AOMs for intensity control. 44 The spectroscopy module includes the optical setup for Doppler-free spectroscopy of either Rb87 or Rb85. The corresponding reference laser is frequency stabilized to a hyperfine transition. The optical setup will be based on the experience in the MAIUS project. A diode laser based laser system provides the laser beams for beam manipulation, cooling, trapping and detection. In the current baseline microintegrated ECDL laser modules, provided by the FerdinandBraun-Institut für Höchst- frequenztechnik, Berlin, are foreseen, in combination with dedicated MOPA (Master Oscillator Power Amplifier) modules. The output powers at the atoms are ~ 0.5 W. The switching and frequency shifting of the laser beams, together with power monitoring and laser pulse generation for the experimental sequence is carried out on the switching module. The current baseline is an adoption of the MAIUS design using a Zerodur baseplate and AOMs for fast switching in combination with mechanical shutters. The distribution module carries out the overlapping and the redistribution of the cooling and repumping light from the switching module using a fiber integrated splitter. The laser beams with different frequencies are overlapped in the Offset Lock module using a fiber splitting unit and focused onto a photodiode for phase-lock. The electronics consists of the following five functional units: (i) Digital Management Unit (DMU) controlling all other electronics units and the overall payload, (ii) Magnetics Drive providing the low noise current drivers for magnetic field generation, (iii) Low-noise RF Generation providing the signals at 6.8 GHz and 3 GHz corresponding to the hyperfine transition in Rb87 and Rb85, respectively, as well as a stable 100 MHz reference signal, (iv) Laser Control providing the low noise current supplies for the lasers, (v) Ion Getter Pump Supply providing the high voltage for the ion getter pump. For the atom interferometer a total mass budget of 265 kg, an average power of 680 W, a peak power of 900 W and a telemetry budget of 110 kbps is allocated (numbers with 20% component contingency and 20% system margin). 45 Laser System for Dual Species Interferometry with 87Rb and 85Rb on STEQUEST M. Krutzik1 for the STE-QUEST team 1 Humboldt-Universität zu Berlin [email protected] Abstract. In this poster we present the overall design, technological details and redundancy architecture of the laser system for the STE-QUEST dual species atom interferometer [1]. It combines a fiber technology based reference and optical dipole trap laser with microintegrated, high power diode laser modules. Laser beam manipulation and switching are realized in Zerodur optical bench technology while fiber optical splitter systems provide the capability for precise distribution of the laser light. The reference laser is based on telecommunication components and frequency doubling technologies. Using frequency modulation spectroscopy (FMS), an error signal is generated and used for feedback on the laser diode for stabilization. The modulation is realized with an all-fibered phase modulator being integrated between the erbium doped fiber amplifier (EDFA) stage and the periodically poled lithium niobate (PPLN) waveguide so that the reference laser must not be current-modulated itself. The same EDFA is used for generating the dipole trap light, see figure 1. The laser sources for cooling, coherent manipulation and detection of 85Rb and 87Rb are microintegrated ECDL-MOPAs (µECDL-MOPAs), since they will combine a micro-integrated, extended cavity diode laser (µECDL) as a master oscillator and a power amplifier (PA) on two microoptical benches (MioB) interconnected with a single-mode optical fiber. They will provide small linewidths and high output power levels at the same time. The µECDL-MOPAs are shifted to their required frequencies as specified by means of offset lock stabilization For switching, combining and distribution the light from the µECDL-MOPAs is guided to one consolidated switching module based on Zerodur optical bench technology. It will control the laser intensity and frequency for the 87Rb- and 85Rb-MOT, for Raman-interferometry, for detection and manipulation of the atoms. The switching and intensity control are realized with a combination of Acousto-optical modulators (AOMs) and mechanical shutters. Finally, fiber optical splitter systems precisely distribute the different laser beams as required by the physics package. Figure 1: Schematic of the laser system (LS) for the STE QUEST dual species atom interferometer (ATI). It is divided into three subsystems: The reference laser and optical dipole trap module (ATI-LSROS), the diode laser package module (ATI-LS-DLP) and the switching and distribution module (ATILS-SAD). All interfaces shown here are pm single mode optical fibers. 46 REFERENCES [1] ESA STE-QUEST mission homepage: http://sci.esa.int/ste-quest 47 An Optical Link for the ACES and STE-QUEST Missions in Western Australia S. Schediwy1, A. Luiten1,2, J. Anstie1,2, A. Griffin3, J. McFerran1, M. Tobar1. 1 2 School of Physics, University of Western Australia, Crawley WA 6009, Australia Institute for Photonics and Advanced Sensing (IPAS) and School of Chemistry & Physics, The University of Adelaide, Adelaide SA 5005, Australia 3 Australia’s Academic and Research Network (AARNet), Kensington WA 6151, Australia [email protected] Abstract. Western Australia is becoming the premier southern hemisphere hub for high-precision ground-space timing missions. The University of Western Australia (UWA) is currently building a state-of-the-art optical atomic clock, and has been selected as the only southern hemisphere microwave-frequency ground station for the Atomic Clock Ensemble in Space (ACES) mission. A dedicated two-way satellite time and frequency transfer link exists between UWA and Australian legal time maintained by the National Measurement Institute. We plan to support the ACES European Laser Timing Experiment (ELT), the Space-Time Explorer and the Quantum Equivalence Principle Space Test (STE-QUEST) mission, by tying the atomic clocks and microwave links at UWA to a satellite laser ranging (SLR) station for ground-to-space time transfer. The Mobile Laser Ranging System (MOBLAS-5), is the most productive SLR station in the International Laser Ranging Service; it is located 330 km north of UWA and close to the perigee of the STE-QUEST satellite. MOBLAS-5 is co-located with the Western Australian Space Centre (WASC) which comprises other geodetic facilities as well as commercial satellite relay operators. Through Australia’s Academic and Research Network (AARNet), we have light-level access to an 820 km fibre link between the Square Kilometre Array (SKA) site and its associated supercomputing facility near UWA. Figure 1 shows that this fibre passes within only 60 km of WASC. We propose to connect WASC to this SKA fibre, and establish an ultra-precise timing link between UWA and WASC. The fibre will also support very-long baseline interferometry radio astronomy and geodesy earth science, as well as provide a high-speed data connection for the commercial and research organisations based at WASC. We plan to utilise a novel microwave-frequency dissemination technique (Schediwy, 2012) developed by Australian researchers as part of the National Time and Frequency Network (NTFN) research programme. This technique utilises the precision of optical-frequencies to sense optical path-length fluctuations of the fibre link, and applies the appropriate correction to stabilise a transmitted microwave-frequency signal. We have demonstrated the validity of this technique in laboratory experiments and are now deploying it across longer lengths of installed fibre networks. FIGURE 1. Map of Western Australia, showing the existing 820 km optical fibre between UWA and the SKA site (blue), as well as the proposed 60 km extension to the MOBLAS-5 satellite laser ranging facility at WASC (red). This optical fibre timing link between WASC and UWA will ensure Western Australia will become the southern hemisphere hub of all future high-precision clocks in space missions. ACKNOWLEDGMENTS This research was supported under Australian Research Council's Linkage Projects (LP110100270) and Future Fellowship (FT0991631) funding schemes. 48 REFERENCES Schediwy, S.W., Luiten, A., Aben, G., Baldwin, K., He, Y., Orr, B., and Warrington, R.B., "Microwave Frequency Transfer with Optical Stabilisation" Proceedings of the 2012 European Frequency and Time Forum, 211-213 (2012). 49 Microwave Generation from Optical Frequency Combs U. Sterr1, B. Lipphardt1, T. Legero1, H. Schnatz1, I. Ernsting2, Q.-F. Chen2, A. Nevsky2, S. Schiller2, 1 2 Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany [email protected] Abstract. The STE-QUEST clock physics package will be based on the PHARAO cesium clock [1], currently being developed in the frame of the ACES mission. To reach a quantum projection limited frequency stability of 8 ⋅ 10 −14 τ and to allow for onboard evaluation of the clock, a low phase noise microwave signal with high stability will be needed, at a performance level exceeding the currently available room temperature microwave oscillators. To fulfil the requirements, the microwave signal will be generated from an ultrastable optical frequency using a femtosecond laser as frequency divider. The optical signal is generated from a 1064 nm Nd:YAG laser, which is frequency-stabilized to a ultrastable, rugged vibration insensitive optical resonator. Its instability is required to be below 3.5⋅10-15 between 1 s and 100 s of integration time after linear drift removal while variations of the drift need to be smaller than shall be smaller than 2⋅1016 /s in a time interval of 1000 s. This optical signal needs to be transferred to the microwave domain without introducing excess phase noise. To this goal, a femtosecond frequency comb based on erbium-doped fibers will be employed. To obtain the required phase noise of the 9.2 GHz signal of 90 dBrad/Hz at 1 Hz, dropping to 120 dBrad/Hz at 1 kHz carrier offset, we currently investigate two approaches. In the first approach, the repetition rate of the femtosecond fiber laser is locked with a wide bandwith intracavity electrooptical modulator to the optical carrier [2]. Here all fluctuations of the comb have to be removed by the servo system. In the second approach, the laser is only loosely locked laser to the optical carrier, with the laser acting as transfer oscillator [3], the remaining fluctuations are measured and mixed to a suitable harmonic of the repetition rate to create a microwave signal independent of the fluctuations. Advantages and disadvantages of the two approached will be presented and the setup for an evaluation of two systems will be described. ACKNOWLEDGMENTS The research leading to these results has received funding from the Bundesministerium für Wirtschaft und Technologie (Germany) under project no. 50OY1201. REFERENCES [1] P. Laurent, M. Abgrall, C. Jentsch, P. Lemonde, G. Santarelli, A. Clairon, I. Maksimovic, S. Bize, C. Salomon, D. Blonde, J. Vega, O. Grosjean, F. Picard, M. Saccoccio, M. Chaubet, N. Ladiette, L. Guillet, I. Zenone, C. Delaroche, and C. Sirmain, “Design of the cold atom PHARAO space clock and initial test results” , Appl. Phys. B 84, 683-690 (2006) [2] W. C. Swann, E. Baumann, F. R. Giorgetta, and N. R. Newbury, “Microwave generation with low residual phase noise from a femtosecond fiber laser with an intracavity electro-optic modulator”, Opt. Express 19, 24387-24395 (2011) [3] B. Lipphardt, G. Grosche, U. Sterr, C. Tamm, S. Weyers, and H. Schnatz, “The stability of an optical clock laser transferred to the interrogation oscillator for a Cs fountain”, IEEE Trans. Instrum. Meas. 58, 1258-1262 (2009) 50 Time and frequency Transfer with the ESA/CNES ACES-PHARAO Mission P. Delva, C. Guerlin, C. Le Poncin-Lafitte, P. Laurent, F. Meynadier, P. Wolf LNE / Syrte – Observatoire de Paris, CNRS, UPMC Univ Paris 06, UMR8630, F-75005, Paris, France Email: [email protected] Abstract. The Atomic Clocks Ensemble in Space (ACES-PHARAO mission1), which will be installed on board the International Space Station in 2016, will realize in space a time scale of very high stability and accuracy. This time scale will be compared to a ground clock network thanks to a dedicated twoway microwave link. For that purpose our team is developing advanced time and frequency transfer algorithms. The altitude difference between the ACES-PHARAO clock and ground clocks will allow to measure the gravitational redshift with unprecedented accuracy, as well as looking for a violation of Lorentz local invariance. Several ground clocks based on different atomic transitions will be compared to look for a drift of fundamental constants. Moreover, the mission will pave the way to a new type of geodetic measurement: the gravitational redshift will be used to measure gravitational potential differences between distant clocks, with an accuracy around 10 cm. 1 Salomon, C., Cacciapuoti, L., & Dimarcq, N. 2007, International Journal of Modern Physics D, 16, 2511 51 Overcoming Loss of Contrast in Atom Interferometry due to Gravity Gradients A. Roura1, W. Zeller1, W. P. Schleich1 1 Institut für Quantenphysik, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany [email protected] Abstract. Long-time atom interferometry in drop towers, sounding rockets and space missions is required for high-precision measurements of fundamental physical properties, including tests of the equivalence principle. Such measurements rely on the dependence of the phase shift between the two branches of a Mach-Zehnder interferometer as a function of the interrogation time and on the corresponding oscillations in the integrated atom density at each exit port. For long times, however, gravity gradients cause the classical trajectories associated with the two branches not to close in phase space, which leads to a spatially dependent phase shift between the two overlapping wave-packets at the exit ports and gives rise to a fringe-pattern density profile. This in turn implies a smaller amplitude of the oscillations in the total number of atoms at each port and a reduction of the interferometer's sensitivity. In fact, this effect alone leads to a 40% loss of contrast in the current plans for STE-QUEST. Here we present a mitigation strategy to overcome such loss of contrast which is very simple to implement. FIGURE 1. Contrast vs. half interferometer time (in seconds) for an expanding BEC in a Mach-Zehnder interferometer including the effects of the Earth's gravity gradient. Blue and red curves correspond to an effective temperature of 1 nK and 70 pK respectively. The contrast at long times is clearly higher when the mitigation strategy is employed (dashed lines) than otherwise (continuous lines). ACKNOWLEDGMENTS This project is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant number 50WM1136. 52 Development of Atomic Clocks and Frequency Transfer Techniques at Three Laboratories around Tokyo Area Y. Hanado1, F.-L. Hong2, H. Katori3,4 1 National Institute of Information and Communications Technology (NICT), 4-2-1, Nukuikita, Koganei, Tokyo, 184-8795, Japan 2 National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Central 3, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan 3 Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan 4 RIKEN, Quantum Metrology Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan [email protected] Abstract. Four laboratories around Tokyo area actively develop state-the-art optical clocks and related techniques. The group at the University of Tokyo and Riken develops Sr lattice clocks and Hg lattice clocks, National Metrology Institute of Japan (NMIJ) develops Yb lattice clock and Sr-Yb lattice clock, and National Institute of Information and Communications Technology (NICT) develops Ca+ clock, In+ clock, and Sr lattice clock. These laboratories are available to link with optical fiber or precise satellite time and frequency transfer, and collaborate together to join the ACES mission if its ground terminal comes in Japan. The group at the University of Tokyo and Riken has been developing optical lattice clocks with spinpolarized fermions in a 1D lattice and unity-occupation bosons in a 3D lattice to suppress atomic interactions and demonstrated frequency comparison of these two clocks to evaluate their performances [1]. By rejecting the Dick effect [2], the Allan standard deviation of 4×10-16/√τ/s was demonstrated [3] to allow exploring 1×10-17 uncertainty in τ ≈ 1,600 s, which corresponded to the QPN limit for N ≈ 1,000 atoms. This group has also been developing the optical lattice clocks with strontium atoms in a cryogenic environment and those with mercury atoms that have one order smaller magnitude of sensitivity to blackbody radiation than that of strontium. The current status of the clock comparison comprising of Sr (x2) and Hg (x2) clocks are being evaluated, both of which are planned to operate without dead time in the future. The frequency comparison of these clocks at 10-18 will allow us to investigate the constancy of fundamental constants with high precision. At NMIJ, two Cs atomic fountain clocks (NMIJ-F1 and NMIJ-F2), two optical clocks (171Yb optical lattice clock and Yb/Sr dual optical lattice clock) and precise frequency transfer systems are being developed. NMIJ-F1 has made the calibration of the International Atomic Time (TAI) 22 times between 2007 and 2011 with a combined uncertainty of 3.9 × 10-15. The construction of NMIJ-F2 has been continued toward an uncertainty of 10-16. As to the 171Yb lattice clock, absolute frequency was determined as 518 295 836 590 863.1(2.0) Hz relative to the SI second [4]. The 87Sr optical lattice clock project has also started for the measurement of the Yb/Sr frequency ratio with an uncertainty beyond the Cs limit [5, 6]. Fiber-based frequency combs with a multi-branch configuration are also developed, which can transfer both linewidth and frequency stability to another wavelength at the millihertz level [7, 8]. (This research related with optical clock receives support from the JSPS through its FIRST Program.) As for the international time and frequency transfer, dual frequency carrier phase GPS receiver is the main tool and the Two Way Satellite Time and Frequency Transfer (TWSTFT) facilities for Asia Pacific link and for Asia-European link are back-up tool. At NICT, two Cs atomic fountain clocks (NICT-CsF1 and NICT-CsF2) and two optical atomic clocks are developed. NICT-CsF1 [9] has been in operation since 2006 and contributes to the determination of TAI with a combined uncertainty of 2 × 10-15. NICT-CsF2 using a pure optical molasses is under development, and most systematic shifts are evaluated at a level below 5E-16 uncertainty. The remaining measurements for mw-related shifts are underway. As for the optical clocks, a single 40Ca+ clock and a 87Sr lattice clock have started operations in 2008, and 2011, respectively. The 40Ca+ and 87 Sr clock transition frequencies were measured with systematic uncertainties of 2.2×10-15 [10] and 5×10-16 [11], respectively.. As a new ion, we started a development of In+ clock. NICT is in charge of the generation and dissemination of JST, time and frequency transfers with PTB and USNO are 53 regularly performed by TWSTFT and GPS. The developments of an advanced TWSTFT technique [12] and optical fiber transfer have been actively conducted. Especially, the agreement of two Sr lattice clocks between NICT and University of Tokyo was confirmed by using this optical fiber noise canceling system [13]. In the presentation, the details of each activity are introduced. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] C. W. Chou, D. B. Hume, J. C. J. Koelemeij†, D. J. Wineland, and T. Rosenband, "Frequency Comparison of Two High-Accuracy Al+ Optical Clocks," Phys. Rev. Lett. 104, 070802 (2010). G. J. Dick, J. D. Prestage, C. A. Greenhall, and L. Maleki, " Local Oscillator Induced Degradation of Medium-Term Stability in Passive Atomic Frequency Standards," in 22nd PTTI Applications and Planning Meeting, p. 487, (1990). M. Takamoto, T. Takano, and H. Katori, "Frequency comparison of optical lattice clocks beyond the Dick limit," Nature Photon. 5, 288 (2011). M. Yasuda, H. Inaba, T. Kohno T. Tanabe, Y. Nakajima, Hosaka, D. Akamatsu, A. Onae, T.Suzuyama, M. Amemiya, and F.-L. Hong, "Improved Absolute Frequency Measurement of the 171Yb Optical Lattice Clock towards a Candidate for the Redefinition of the Second," Appl. Phys. Express, 5, 102401 (2012). D. Akamatsu, M. Yasuda, T. Kohno, K. Hosaka, and F.-L. Hong, "A compact light source at 461 nm using a periodically poled LiNbO3 waveguide for strontium magneto-optical trapping," Opt. Express 19, 2046 (2011). D. Akamatsu, Y.Nakajima, H. Inaba, K. Hosaka, M. Yasuda, A. Onae, and F.-L. Hong, "Narrow linewidth laser system realized by linewidth transfer using a fiber-based frequency comb for the magneto-optical trapping of strontium," Opt. Express 20, 16010 (2012). Y. Nakajima, H. Inaba, K. Hosaka, K. Minoshima, A. Onae, M. Yasuda, T. Kohno, S. Kawato, T. Kobayashi, T. Katsuyama, and F.-L. Hong, "A multi-branch, fiber-based frequency comb with millihertzlevel relative linewidths using an intra-cavity electro-optic modulator," Opt. Express 18, 1667 (2010). K. Iwakuni, H. Inaba, Y. Nakajima, T. Kobayashi, K. Hosaka, A. Onae, and F.-L. Hong, "Narrow linewidth comb realized with a mode-locked fiber laser using an intra-cavity waveguide electro-optic modulator for high-speed control," Opt. Express 20, 13769 (2012). M. Kumagai,H. Ito, M. Kajita, and M. Hosokawa "Evaluation of caesium atomic fountain NICT-CsF1," Metrologia 45 139 (2008). K. Matsubara, H. Hachisu, Y. Li, S. Nagano, C. Locke, A. Nogami, M. Kajita, K. Hayasaka, T. Ido, and M. Hosokawa, "Direct comparison of a Ca+ single-ion clock against a Sr lattice clock to verify the absolute frequency measurement," Opt. Express 20, 22034 (2012). A. Yamaguchi,N. Shiga, S. Nagano, Y. Li, H. Ishijima, H. Hachisu, M. Kumagai, and T. Ido."Stability Transfer between Two Clock Lasers Operating at Different Wavelengths for Absolute Frequency Measurement of Clock Transition in 87Sr," Appl. Phys. Express 5, 022701 (2012). M. Fujieda, T. Gotho, F. Nakagawa, R. Tabuchi, M. Aida, and J. Amagai, "Carrier-Phase-Based Two-Way Satellite Time and Frequency Transfer," IEEE TUFFC, 59, 12, 2625 (2012). M. Fujieda, M. Kumagai, S. Nagano, A. Yamaguchi, H. Hachisu, and T. Ido, "All-optical link for direct comparison of distant optical clocks,", Opt. Express 19 16498 (2011). 54 Features of the STE-QUEST S/C Design with Focus on Instrument Interfaces, Telecommand & Data Handling, and Science Links G. Hechenblaikner1, M-P Hess1, J Beck1, M. Williams2, Astrium Study Team1,2 1 2 Astrium GmbH, Satellites, 88039 Friedrichshafen, Germany Astrium Ltd., Gunnels Wood Road, Stevenage, SG1 2AS, United Kingdom [email protected] Abstract. Space-Time-Explorer-Quantum Equivalence Principle Space Test (STE-QUEST) is an Mclass mission candidate for launch in 2022/2024 in the ESA Cosmic Vision programme. It was selected by the European Space Agency for an assessment study until mid-2013, which started with an ESAinternal assessment, followed by ongoing mission assessment studies performed by competitive industrial teams. We report on preliminary results of the mission assessment under the lead of EADS Astrium. Some basic features of the mission design are discussed and specific design concepts of the spacecraft, science payload and time and frequency links are briefly reviewed. Starting with an overview over mission objectives and derived science requirements we discuss their impact on the mission and system design. A rough sketch of the baseline design of the spacecraft is given and the design choice for certain subsystems and operation strategies is discussed in light of the key requirements. Design aspects with particular relevance to the two instruments, the atom interferometer and the atomic clock, are given special emphasis. Among those payload relevant topics, instrument interfaces, payload accommodation, anticipated data rates and ground contact times are further elaborated. We conclude with a short summary of the science link and precise-orbit-determination design and review associated performance features. 55 Towards a free space satellite to ground coherent optical link N. Chiodo1, P. Wolf1, K. Djerroud1, O. Acef1, G. Santarelli1 E. Samain2, J. Paris2, B. Fleury3, J. Montri3, C. Petit3 1 2 LNE-SYRTE, Observatoire de Paris, CNRS, UPMC, Paris, France Géo-Azur, Observatoire de la Côte d’Azur, CNRS, Grasse, France 3 DOTA, ONERA, Chatillon, France [email protected] Abstract. Coherent links are based on the direct measurement of the optical phase rather than an amplitude modulation (pulses) as in conventional laser ranging. A limiting factor in this kind of links is the time variation of the refractive index of the terrestrial atmosphere due to the turbulence phenomenon that adds phase noise and intensity fluctuations both decreasing the performance of the link. Based on first results of a ground-ground coherent link1 with 5 km propagation through the turbulent atmosphere we estimate the potential performance of such links for ground to space frequency comparison of clocks, showing that significant improvement with respect to existing methods can be expected, potentially down to 10-17 in relative frequency in less than 1000 s integration time. Our next step towards this goal is the experimental realization of a link from a ground telescope to a low Earth orbit (LEO) satellite equipped with corner cube reflectors. We describe the requirements on the laser system for such a link (stability at the 10-13 level or below, whilst being tunable over 20 GHz) and present our solution for that challenge showing the performance of our laser system. We describe first (unsuccessful) experiments that took place in November 2012, January 2013 and March 2013 at the 1.5 m lunar ranging telescope of the Côte d’Azur Observatory in collaboration with ONERA (French aerospace lab) who provides the adaptive optics bench. We discuss the encountered challenges and difficulties, and the implemented or planned solutions. ACKNOWLEDGMENTS Helpful discussions with Sébastien Bize are greatfully acknowledged. This work was supported by CNES research grant (R-S09/SU-0001-021) DA 10069354, financing by LNE and by the Action Spécifique GRAM (INSU/INP/CNES). REFERENCES Djerroud K., et al., “Coherent Optical Link Through the Turbulent Atmosphere”, Opt. Lett. 35, 1479-1481 (2010). 56 STE-QUEST: TAS Assessment Study Main Outcomes A.Ferri1, C.Dufour2, L.Bonino1, A.Marcer1, M.Siccardi5 , D.Grana1 1 Thales Alenia Space Italy, Strada Antica di Collegno 253, 10146 Turin, Italy 2 Thales Alenia Space France, Boulevard du Midi, Cannes, France 5 M. Siccardi, SKK,Via XX Settembre, 30, 12100 Cuneo, Italy [email protected] Abstract. This paper presents the results of 1-year and a half assessment study performed by the THALES ALENIA SPACE Team for the European Space Agency on the STE-QUEST mission, a medium –class mission planned for the next decade to test the different aspects of Einstein’s Equivalence Principle using quantum sensors. This paper highlights the major complexities encountered during the study activities, which reflect the challenging scientific and technological aspects of the mission, and the proposed solutions (the drag free control, the solar array rotation and attitude control strategy, the impact of the environment, the implementation of the scientific link). Nonetheless, this demanding mission is deemed feasible, and a short summary of the major aspects of the S/C design is illustrated. Also, the activities performed on the End to End Performance Model are summarized with methods and results. The developed software models the typical behavior of the Scientific Links between the STE-QUEST spacecraft and the dedicated ground terminal, located in Turin, both in the radiofrequency and in the optical fields, assessing their accuracy and stability performances. The model takes into account the factors affecting the time and frequency transfer, in particular the effects which are not compensated by the two-way links’ structure, such as atmospheric influence on the different frequencies, orbit dynamics, hardware and thermal issues. 57 Microwave Link Design and Optical Link Design for Future Scientific Space Missions T. Feldmann, W. Schäfer TimeTech GmbH, Curiestr. 2, 70563 Stuttgart, Germany [email protected] Abstract. During the last years significant progress has been achieved in the field of optical atomic clocks, exceeding traditional microwave clocks and the capabilities of current time and frequency transfer via satellites by more than two orders of magnitude. The best optical frequency standards reach fractional frequency instabilities of a few parts in 10-17 after 1000 s integration time and fractional frequency uncertainties of few parts in 1018. This level of performance requires the introduction of new techniques for metrological time and frequency comparisons. Applications include relativistic geodesy and fundamental physics research. Consequently, high performance links and optical clocks have been proposed in the ESA Cosmic Vision program as key technology to probe fundamental laws of physics, like gravitational redshift measurements to detect violations of the Local Position Invariance (LPI) principle, light propagation tests including Shapiro delay, and other fundamental research, such as time variations of fundamental constants and scale dependent gravity. A technology development study has been performed by TimeTech GmbH, in cooperation with the national metrology laboratories of Germany (PTB), France (LNE-SYRTE), and UK (NPL), the German national aeronautics and space research centre (DLR), and the French aerospace lab (ONERA), with the aim of designing and developing a metrology link for high performance frequency comparisons of clocks between space and ground. The results of this activity are important both to support future ESA missions in the field of fundamental physics and to provide clocks on ground with the necessary means to connect them in a worldwide network. Emphasis was on the comparison of clocks through the turbulent atmosphere (space-to-ground link) with frequency uncertainty at the 10-18 level and frequency stability of 10-18 at 10000 s integration time. The achievable performance shall bridge the gap between recent clock developments and available time/frequency comparison and ranging techniques and it shall be sufficient to support future ESA missions in the field of fundamental physics, such as the proposed Space-Time Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. The relevant technical parameters and limitations were analyzed in detail and two prospective approaches were identified: Bi-directional optical link (OL) and bi-directional microwave link (MWL). The proposed links were investigated as candidate metrological systems for the STE-QUEST mission. The compliance with its requirements is feasible by building on experience with current systems together with moderate improvements in a few, well-defined technological areas. ACKNOWLEDGMENTS We would like to thank G. Grosche (PTB), D. Piester (PTB), H. Schnatz (PTB), P. Wolf (LNESYRTE), C. Robert (ONERA), D. Giggenbach (DLR), R. MataCalvo (DLR), M. Hoque (DLR), and J. Davis (NPL) for their contributions to the study and their outstanding cooperation. We acknowledge TESAT GmbH for valuable support. 58 The Cosmological Context P. Binétruy 1 APC, Université Paris Diderot, CNRS, CEA, Obervatoire de Paris and Sorbonne Paris Cité Paris, France Abstract. The era of precision measurement that cosmological observations have now reached constrains the models of fundamental physics that may explain some of the central concepts, in particular inflation and dark energy. This relationship will be illustrated on specific examples and it will be shown that, in many cases, this leads to violations of the Einstein equivalence principle. 59 Towards a Space-Qualified High-Finesse Cavity for Optical Clocks G. P. Barwood1, R. A. Williams1, S. A. Webster1,2 and P. Gill1 1 National Physical Laboratory, Hampton Road, Teddington, Middx TW11 0LW Present Address: M Squared Lasers Ltd, West of Scotland Science Park, Maryhill Rd, Glasgow, G20 0SP 2 [email protected] Abstract. A high finesse optical cavity targeted on space applications has been developed, comprising a compact cubic spacer (L = 50 mm) with low sensitivity to acceleration [Webster 2011]. In order to characterise the cavity, a pair of longer cavities (L = 300 mm) with parts in 1016 relative frequency stability is also being developed. Three YAG lasers at 1064 nm can be independently locked to these three cavities. Locking of a 1064 nm fibre laser to the cubic cavity has also been demonstrated. This poster will discuss the current status of both cavity types. The cubic cavity spacer has demonstrated the lowest passive sensitivity to acceleration to date with a maximum sensitivity along any of the three principal axes of 2.5 x 10-11/g (g = 9.81 m/s2). The cavity is mounted symmetrically via four hemispherical nylon supports in a tetrahedral configuration, pressured at up to 100 N. Whilst this mounting arrangement works well under conditions of low acceleration, consideration needs to be given to the conditions encountered during the non-operational phases of space launch and deployment, where transient accelerations of up to 80g could be experienced, together with temperature cycling of ~50°C. The existing cubic cavity spacer is manufactured from a ULE sample that was not specially selected for zero linear thermal expansion close to room temperature, and has fused silica mirrors; the measured thermal expansion is 25 MHz/K. Future cubic cavities with ULE material with a zero linear thermal expansion at more convenient temperatures will allow a frequency stability close to the ~1 x 10-15 thermal noise limit. In order to characterise the cubic cavity design, a pair of high finesse cavities with ~300 mm spacers has been developed, where a reduced thermal noise limit for the cavities is achieved via their long spacer lengths and fused silica mirrors [Notcutt 2006]. Use of silica mirrors increases the overall linear thermal expansion of the cavity and so a novel approach has been adopted to develop a thermally compensated cavity. This differs from the approach adopted by PTB [Legero 2010] by using a reentrant mirror design. Finite element modelling indicates that the temperature where the effective linear thermal expansion is zero should be 25°C, close to the measured crossover temperature of 24.4°C. Beat frequency measurements between two YAG lasers locked to independent 300-mm cavities demonstrate an Allan deviation of ~8 parts in 1016 (5.7 parts in 1016 single laser stability) at 1 s. ACKNOWLEDGMENTS This work is supported by the UK and European Space Agencies, the UK Technology Strategy Board and the National Physical Laboratory Strategic Research Programme. REFERENCES Legero, T. Kessler, T. and Sterr U, “Tuning the thermal expansion properties of optical reference cavities with fused silica mirrors”, J. Opt. Soc. Am. B 27, No. 5/May 2010 Notcutt M, Ma, L-S, Ludlow A.D, Foreman, S.M, Ye J. and Hall J.L., “Contribution of thermal noise to frequency stability of rigid optical cavity via Hertz-linewidth lasers” Phys Rev A, 73, 031804(R) (2006) Webster S.A. and Gill P., “Force-insensitive optical cavity”, Optics Letters, 36, 3572-3574 (2011) 60 STE-QUEST - Geodetic Mission for Terrestrial and Celestial Reference Frame Realization D. Svehla, M. Rothacher, A. Nothnagel, U. Hugentobler, P. Willis, R. Biancale, M. Ziebart, G. Appleby ETH Zurich, University of Bonn, TU München, Institut Physique du Globe de Paris, CNES, UCL London, NERC UK [email protected] The Space-Time Explorer and QUantum Equivalence Principle Space Test (STE-QUEST) is the Medium Class fundamental physics mission pre-selected for the M3 slot of the ESA Cosmic Vision Programme. If finally selected in 2013/2014, the highly elliptical orbit of STE-QUEST satellite can be used for the terrestrial reference frame (TRF) realization by means of onboard GNSS, SLR and VLBI radio source (microwave metrology link - compatible with VLBI2010). By upgrading the onboard GNSS receiver for DORIS tracking, the STE-QUEST mission will be equivalent to the GRASP mission proposal from JPL or a similar mission proposals followed by ETH Zurich and GFZ Potsdam for terrestrial reference frame realization. However, the highly elliptical orbit of STE-QUEST provides advantages for terrestrial and celestial reference frame determination (e.g. VLBI tracking in apogee), compared to the GRASP mission proposal limited to the LEO orbit only. We present science objectives of the STE-QUEST mission related to geodesy. In particular we will show how STE-QUEST can - meet the GGOS (Global Geodetic Observing System) goals for terrestrial reference frame of the Earth, i.e. 1 mm accuracy and 0.1 mm/yr stability of the TRF - significantly improve satellite altimetry and tide gauge records of global mean sea level rise by using highly accurate TRF from the STE-QUEST mission - contribute to mass transport in polar regions (ice mass loss) by referencing altimetry (Cryosat, ICESat) and gravity data (GRACE, GOCE) to the common TRF from the STE-QUEST mission - determine the long-wavelength variability in the gravity field of Earth (central term and J2) that are either not observed or poorly observed by GRACE (e.g. J2) - be used for the realization of both, the terrestrial and the celestial reference frame of the Earth with zenith pointing phased array GNSS antenna, observing GNSS (and VLBI) signals - improve orbit accuracy of GNSS satellites by one order of magnitude - contribute to the monitoring of the Earth rotation and orientation parameters making use of the highly elliptical orbit of the STE-QUEST mission (UT1 etc.) and VLBI tracking from the ground (quasars/GNSS satellites) - provide a common time scale for all space geodesy techniques (GNSS, DORIS, VLBI and SLR) - disseminate TRF and time anywhere on Earth or in space - be used for operational relativistic geodesy 61 Quantum Mechanics and the Equivalence Principle Domenico Giulini Institut für Theoretische Physik,Leibniz Universität Hannover Appelstrasse 1, D-30167 Hannover, Germany [email protected] Einstein's Equivalence Principle (EEP) has been expressed in a variety of ways, most of which using notions and idealisations from classical physics, which do not easily apply to Quantum Mechanics (QM). There seems to be some confusion in the literature as to whether QM either obeys, eludes, or even contradicts EEP. However, whatever the precise wording might be, the intended impact of any formulation of EEP must be that gravity can be absorbed into geometry. Keeping that in mind, the amount of confusion, I will argue, can be considerably reduced. Finally I apply this to the problem of gravitational self coupling in the semi-classical framework of the Einstein-Klein-Gordon system, which in the 1/c → 0 approximation results in the Schroedinger-Newton equation. Its gravitationally induced collapse behaviour will be illustrated. 62
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