Quantum Physics UltraCold Matter Seth A M Aubin
Quantum Physics & Ultra-Cold Matter Seth A. M. Aubin Dept. of Physics College of William and Mary December 16, 2009 Washington, DC
Outline Ø Quantum Physics: Particles and Waves Ø Intro to Ultra-cold Matter What is it ? How do you make it ? Bose-Einstein Condensates Degenerate Fermi Gases Ø 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 h Pat A P LASER source h at B
Light as a wave LASER source 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 path A LASER source path B screen
… but, Matter is a
Outline Ø Quantum Physics: Particles and Waves Ø Intro to Ultra-cold Matter What is it ? How do you make it ? Bose-Einstein Condensates Degenerate Fermi Gases Ø What can you do with ultra-cold matter
What’s Ultra-Cold Matter ? m. K Ø Very Cold μK Typically nano. Kelvin – micro. Kelvin n. K Atoms/particles have velocity ~ mm/s – cm/s Ø 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 m. K Dilution refrigerator, ~ 2 m. K [priceofoil. org, 2008] μK Ultra-cold quantum temperatures n. K
Ultra-cold Quantum Mechanics Room temperature: Ø Matter waves have very short wavelengths. Ø Matter behaves as a particle. Ultra-Cold Quantum temperatures: Ø Matter waves have long wavelengths. Ø Matter behaves as a wave. Room temperature Quantum régime
Quantum Statistics Bosons Integer spin: photons, 87 Rb. Fermions ½-integer spin: electrons, protons, neutrons, 40 K. 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 Ø Very tight confinement. Ø Fast evaporation time. Ø photo-lithographic production. Ø Integration of complex trapping potentials. Ø Integration of RF, microwave and optical elements. Ø 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
87 Rb BEC RF@1. 740 MHz: RF@1. 725 MHz: RF@1. 660 MHz: N = 7. 3 x 105, T>Tc N = 6. 4 x 105, T~Tc N=1. 4 x 105, T<Tc
87 Rb BEC RF@1. 740 MHz: RF@1. 725 MHz: RF@1. 660 MHz: N = 7. 3 x 105, T>Tc N = 6. 4 x 105, T~Tc N=1. 4 x 105, T<Tc ~ K n 0 0 5 Surprise! Reach Tc with only a 30 x loss in number. (trap loaded with 2 x 107 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 Bose. Einstein condensation in 87 Rb and 23 Na.
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 40 K atoms sympathetically with an 87 Rb BEC. “Iceberg” BEC Fermi Sea
Sympathetic Cooling Low temperature “High” temperature Quantum Behavior
Outline Ø Quantum Physics: Particles and Waves Ø Intro to Ultra-cold Matter What is it ? How do you make it ? Bose-Einstein Condensates Degenerate Fermi Gases Ø 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: 87 Rb atom @ v=1 m/s atom 5 nm. green photon 500 nm. 2 orders of magnitude increase in resolution at v=1 m/s !!! Mach-Zender atom Interferometer: Path A D 1 Path B D 2
Atomic Clocks Ø Special type of atom interferometer. Ø Temporal interference, instead of spatial. Ø Most accurate time keeping devices that exist. Ø State-of-the-art: accuracy of 1 part in 1016 … 16 digits !!! Applications: Ø Keeping time. Ø GPS Navigation. Ø Deep space navigation.
Summary Ø Quantum Physics Ø Ultra-cold atom technology Ø Matter-wave interferometry
Ultra-cold atoms group Francesca Fornasini Brian Richards Prof. Seth Aubin Lab: room 15 Office: room 333 saaubi@wm. edu Megan Ivory Austin Ziltz Jim Field Yudistira Virgus
Thywissen Group D. Mc. Kay B. Cieslak S. Myrskog A. Stummer Colors: Staff/Faculty Postdoc Grad Student Undergraduate M. H. T. Extavour L. J. Le. Blanc T. Schumm J. H. Thywissen
- Slides: 42