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Quantum Physics & Ultra-Cold Matter Seth A. M. Aubin Dept. of Physics College of William and Mary December 16, 2009 Washington, DC Outline Quantum Physics: Particles and Waves Intro to Ultra-cold Matter What is it ? How do you make it ? Bose-Einstein Condensates Degenerate Fermi Gases What can you do with ultra-cold matter Quantum Physics Summary or “take home message”: 1. It’s weird defies everyday common sense. Quantum Physics Summary or “take home message”: 1. It’s weird defies everyday common sense. 2. LIGHT behaves as both a PARTICLE and a WAVE. Quantum Physics Summary or “take home message”: 1. It’s weird defies everyday common sense. 2. LIGHT behaves as both a PARTICLE and a WAVE. 3. Matter (i.e. atoms) behaves as both a PARTICLE and a WAVE. Quantum Physics Summary or “take home message”: 1. It’s weird defies everyday common sense. 2. LIGHT behaves as both a PARTICLE and a WAVE. 3. Matter (i.e. atoms) behaves as both a PARTICLE and a WAVE. 4. If something is in 2 PLACES AT ONCE, then it will INTERFERE. Quantum Physics Summary or “take home message”: 1. It’s weird defies everyday common sense. 2. LIGHT behaves as both a PARTICLE and a WAVE. 3. Matter (i.e. atoms) behaves as both a PARTICLE and a WAVE. 4. If something is in 2 PLACES AT ONCE, then it will INTERFERE. 5. Quantum physics is science’s most accurate theory. Quantum Physics Summary or “take home message”: 1. It’s weird defies everyday common sense. 2. LIGHT behaves as both a PARTICLE and a WAVE. 3. Matter (i.e. atoms) behaves as both a PARTICLE and a WAVE. 4. If something is in 2 PLACES AT ONCE, then it will INTERFERE. 5. Quantum physics is science’s most accurate theory. Quantum Accuracy Electron’s g-factor: ge = 2.002 319 304 362 12-digits Theory and experiment agree to 9 digits. [Wikipedia, 2009] Light as a wave LASER source Screen Light as a wave LASER source Screen Light as a wave LASER source Screen Light as a wave LASER source Light as a wave Intensity hA Pat th Pa LASER source B angle screen Also works for single photons !!! [A. L. Weiss and T. L. Dimitrova, Swiss Physics Society, 2009.] Experiment uses a CCD camera (i.e. sensor in your digital camera). Photons follow 2 paths simultaneously Intensity hA Pat path A LASER source th Pa B path B angle screen … but, Matter is a Outline Quantum Physics: Particles and Waves Intro to Ultra-cold Matter What is it ? How do you make it ? Bose-Einstein Condensates Degenerate Fermi Gases What can you do with ultra-cold matter What’s Ultra-Cold Matter ? mK Very Cold μK Typically nanoKelvin – microKelvin nK Atoms/particles have velocity ~ mm/s – cm/s Very Dense … in Phase Space p p x Different temperatures Same phase space density p x x Higher phase space density How cold is Ultra-Cold? 1000 K room temperature, 293 K Antarctica, ~ 200 K K mK Dilution refrigerator, ~ 2 mK [priceofoil.org, 2008] μK Ultra-cold quantum temperatures nK Ultra-cold Quantum Mechanics Room temperature: Matter waves have very short wavelengths. Matter behaves as a particle. Ultra-Cold Quantum temperatures: Matter waves have long wavelengths. Matter behaves as a wave. Room temperature Quantum régime Quantum Statistics Bosons Integer spin: photons, 87Rb. Fermions ½-integer spin: electrons, protons, neutrons, 40K. Bose-Einstein Condensate (BEC) Degenerate Fermi Gas (DFG) All the atoms go to the absolute bottom of trap. Atoms fill up energy “ladder”. How do you make ULTRA-COLD matter? Two step process: 1. Laser cooling Doppler cooling Magneto-Optical Trap (MOT) 2. Evaporative cooling Micro-magnetic traps Evaporation Magneto-Optical Trap (MOT) ~ 100 K Micro-magnetic Traps Advantages of “atom” chips: Iz Very tight confinement. Fast evaporation time. photo-lithographic production. Integration of complex trapping potentials. Integration of RF, microwave and optical elements. Single vacuum chamber apparatus. [Figure by M. Extavour, U. of Toronto] Evaporative Cooling Remove most energetic (hottest) atoms Wait for atoms to rethermalize among themselves Macro-trap: low initial density, evaporation time ~ 10-30 s. Micro-trap: high initial density, evaporation time ~ 1-2 s. Evaporative Cooling Remove most energetic (hottest) atoms P(v) Wait for atoms to rethermalize among themselves Wait time is given by the elastic collision rate kelastic = n v Macro-trap: low initial density, evaporation time ~ 10-30 s. Micro-trap: high initial density, evaporation time ~ 1-2 s. v 87Rb BEC [email protected] MHz: [email protected] MHz: [email protected] MHz: N = 7.3x105, T>Tc N = 6.4x105, T~Tc N=1.4x105, T<Tc 87Rb BEC [email protected] MHz: [email protected] MHz: [email protected] MHz: N = 7.3x105, T>Tc N = 6.4x105, T~Tc N=1.4x105, T<Tc Surprise! Reach Tc with only a 30x loss in number. (trap loaded with 2x107 atoms) Experimental cycle = 5 - 15 seconds BEC History 1925: 1924: S. N. Bose describes the statistics of identical boson particles. A. Einstein predicts a low temperature phase transition, in which particles condense into a single quantum state. 1995: E. Cornell, C. Wieman, and W. Ketterle observe BoseEinstein condensation in 87Rb and 23Na. Fermions: Sympathetic Cooling Problem: Cold identical fermions do not interact due to Pauli Exclusion Principle. No rethermalization. No evaporative cooling. Solution: add non-identical particles Pauli exclusion principle does not apply. We can cool fermionic 40K atoms sympathetically with an 87Rb BEC. “Iceberg” BEC Fermi Sea Sympathetic Cooling Low temperature “High” temperature Quantum Behavior Outline Quantum Physics: Particles and Waves Intro to Ultra-cold Matter What is it ? How do you make it ? Bose-Einstein Condensates Degenerate Fermi Gases What can you do with ultra-cold matter Atom Interferometry Spatial interferometry Precision measurements of forces. Time-domain interferometry atomic clock. BEC Interferometry Spatial Atom Interferometry IDEA: replace photon waves with atom waves. atom photon Example: 87Rb atom @ v=1 m/s atom 5 nm. green photon photon 500 nm. 2 orders of magnitude increase in resolution at v=1 m/s !!! Mach-Zender atom Interferometer: Path A D1 Path B D2 Atomic Clocks Special type of atom interferometer. Temporal interference, instead of spatial. Most accurate time keeping devices that exist. State-of-the-art: accuracy of 1 part in 1016 … 16 digits !!! Applications: Keeping time. GPS Navigation. Deep space navigation. Summary Quantum Physics. Ultra-cold atom technology. Matter-wave interferometry. Ultra-cold atoms group Francesca Fornasini Brian Richards Prof. Seth Aubin Lab: room 15 Office: room 333 [email protected] Megan Ivory Austin Ziltz Jim Field Yudistira Virgus Thywissen Group D. McKay B. Cieslak S. Myrskog A. Stummer Colors: Staff/Faculty Postdoc Grad Student Undergraduate M. H. T. Extavour L. J. LeBlanc T. Schumm J. H. Thywissen