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Observing Radiation Pressure Shot Noise on a Solid Object Cindy Regal Tom Purdy Bob Peterson Ben Yu KITP, QuControl, 2013 0.5 mm Boulder, CO, USA Orientation and outline • (Quantum) Cavity Optomechanics Measure and control motion of objects in interferometers near quantum limits • One degree of freedom • larger – size, mass • complex? Ligo.caltech.edu 0.5 mm x Outline • Experiment presented: Observation of radiation pressure shot noise (RPSN) • Backaction branch of quantum-limited continuous position measurement (fixed meas. time) • (Quantum) Cavity Optomechanics Measure and control motion of objects in interferometers near quantum limits P / P SQL Ligo.caltech.edu 0.5 mm Outline • Experiment presented: Observation of radiation pressure shot noise (RPSN) • Backaction branch of quantum-limited continuous position measurement • Physical object: Very thin vibrating membrane • Si3N4 (50 nm by mm-scale) (fixed meas. time) • (Quantum) Cavity Optomechanics Measure and control motion of objects in interferometers near quantum limits P / P SQL Ligo.caltech.edu 0.5 mm Outline • (Quantum) Cavity Optomechanics Measure and control motion of objects in interferometers near quantum limits • Experiment presented: Observation of radiation pressure shot noise (RPSN) • Backaction branch of quantum-limited continuous position measurement • Physical object: Very thin vibrating membrane • Si3N4 (50 nm by mm-scale) GHz l L • Quantum information applications • Mechanically mediated interactions • Microwave - Optical Ligo.caltech.edu MHz metal 0.5 mm C dielectric Electromechanics: Lehnert Group (JILA) Introduction Heisenberg uncertainty and precision measurement Heisenberg Microscope: Always some physical origin Heisenberg’s book, 1930… Free mass limit Measure to Dx at time t Momentum uncertain to Dp ³ / 2Dx At later time… Dx(t ') = Dx(t) + (t '- t) 2mDx(t) See for example: Braginsky and Thorne, Science (1980) Walls and Milburn, Quantum optics Our version Movable End Mirror Detector lots of photons (108) Shot noise harmonic oscillator N Shot noise of radiation pressure drives up mirror Full answer – modern quantum optics Standard Quantum Limit Shot noise Imprecision White Sz RPSN Backaction White SF Szimp SFba ³ Our measurements focus on behavior at resonance w m Zero Point Motion PSQL Measurement strength, laser power Frequency Frequency c m (w ) SF (w ) 2 Frequency Standard Quantum Limit Shot noise Imprecision White Sz Thermal motion Technical noise Optical power limits … Our measurements focus on behavior at resonance w m RPSN Backaction White SF Zero Point Motion PSQL Measurement strength, laser power Frequency Frequency c m (w ) SF (w ) 2 Frequency Subset of spectrum of optomechanics experiments Optomechanics Electromechanics Effectively moving mirrors Moving capacitor plate trapped atoms Kippenberg, EPFL Lehnert/Simmonds, Boulder Piezoelectrics Painter, Caltech Gravitational wave detectors Cleland/Martinis UCSB Closely related optomechanics experiments Optomechanics Electromechanics Effectively moving mirrors Moving capacitor plate Kippenberg, EPFL Lehnert/Simmonds, Boulder “Laser” cooling to near the mechanical ground state (combined with cryogenic cooling) Painter, Caltech Frequency Observation of sideband asymmetry, Painter group Frequency Closely related optomechanics experiments trapped atoms Observation of RPSN heating with atom gas And ponderomotive squeezing Stamper-Kurn group, Berkeley Frequency Closely related optomechanics experiments Experimental studies of classical analogs: Heidmann group, Paris Frequency Gravitational wave detectors Our optomechanical device (2,2) drum mode • Stoichiometric silicon nitride* sits in optical standing wave near end of cavity • 50 nm thick drum - highly stressed, nm=1 MHz • Increases oscillator energy compared to thermal scales while keeping dissipation similar Q ~ 10 6 -10 7 Transmission Cavity resonance shifts with membrane position Laser Frequency *Introduced to optomechanics: Harris group at Yale, Thompson et al. Nature 2008 A cryogenic, three-element Fabry-Perot cavity 0.5 mm Challenge: • Stability and alignment of cryogenic device Membrane Mirror Piezoelectric Actuator Invar Spacer Membrane Optical Mode Cryogenic optomechanical device device Cryogenic optomechanical Experiment at 4 kelvin – simple in many ways RPSN experiment setup PD Membrane Signal Beam PD PBS PBS Mirror Mirror Meter Beam “Signal Beam (S)” High Power On resonance RPSN Optical force readout “Meter Beam (M)” Low Power Red detuned Optical damping/cooling Displacement readout T. P. Purdy, et al., Science (2013) P. Verlot, et al., PRL (2009) Observing radiation pressure shot noise heating Meter Beam Dominant damping Domin 4He Cryostat T0 = 5 K G M =1.4 kHz Three heat baths at different temperatures coupled to the resonator with differing strengths Signal Beam RPSN G 0 = 0.5 Hz T0 G 0 + TM G M + TS G S Teff = G0 + GM + GS Equilibrium Temperature Radiation pressure shot noise heating RPSN C 1 ~ Frequency Thermal nth 1+ ( kw/2m ) 2 100 Thermal Motion 10 Zero Point Motion SQL 1 0.01 0.1 1 10 100 Parameters for seeing RPSN heating RPSN C 1 ~ Frequency Thermal nth 1+ ( kw/2m ) 2 Cooperativity photon number coupling 4Ng 2 C= kG 0 cavity damping mechanical damping Thermal phonons (4 K bath) nth = kbT0 wm Meter beam damping: • Plays no role in this ratio • (Very important) convenience Radiation pressure shot noise heating kHz Device A Q0=3X106 Frequency (MHz) 100 Device B Q0=1.4X107 10 Thermal Motion 1 10 100 Check for physical heating 3 (2,2) mode well coupled 2 1 (4,4) mode poorly coupled 0 0 1 2 3 4 Signal beam: Record of optical force Meter PD Membrane 1.54 1.55 1.56 Signal PD PBS Mirror Mirror 1.54 1.55 1.56 Frequency (MHz) • AM quadrature - shot noise intensity fluctuations - record of the optical force on the resonator Two beam cross correlation Cross correlation between meter & signal 10-26 0.15 10-28 Contributions: • RPSN to thermal 40% • Loss (ports, path, QE) 40% 10-30 1.54 1.55 Frequency (MHz) 1.56 Two beam cross correlation Test for trivial correlations Mechanical Transducer Excess Membrane Motion PZT White Noise 10-26 10-15 10-28 10-16 10-30 1.54 1.55 1.56 Frequency (MHz) 1.54 1.55 1.56 Frequency (MHz) Classical intensity noise limit Intensity Modulator Excess Intensity Noise White Noise 10-24 10-26 10-28 10-30 1.54 1.55 1.56 Frequency (MHz) Consistency with quantum noise Vacuum Noise from the input port in phase Classical Laser Noise phase shift Vacuum Noise from the output port classical noise (mostly) quantum noise 270 180 90 1.54 1.55 1.56 Frequency (MHz) Microwave to optical quantum link GHz l L C MHz metal dielectric Electromechanics: Lehnert Group (JILA) Analogous experiments: UCSB See for ideas: J. Zhang…S. L. Braunstein, PRA (2003) C. A. Regal and K. W. Lehnert, J. Phys. Conf. Series (2011) A. Safavi-Naeini…O. Painter, New J. Phys. (2011) J. Taylor et al., PRL (2011) T. Palomaki…K. W. Lehnert, Nature in press (2013) 4Ng2 C= > nth kG 0 Transfer rate between phonons and (itinerant) photons exceeds rate at which single phonon leaves to environment Conclusions and directions • To do − Standard quantum limit for continuous position measurement • There is a lot of quantum optics to pursue in these systems, optical squeezing, backaction evasion,… • Elucidating to study these with physical object in interferometer driven by quantum noise Collaborators: Konrad Lehnert Group, JILA Ray Simmonds Group, NIST Group members: Optomechanics Bob Peterson Ben Yu Thomas Purdy Single neutral atoms Adam Kaufman Brian Lester