NanoKelvin Quantum Engineering. Subhadeep Gupta UW NSF-INT Phys REU, 28 th July 2014

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1 NanoKelvin Quantum Engineering Subhadeep Gupta UW NSF-INT Phys REU, 28 th July 2014

2 NanoKelvin Quantum Engineering with Ultracold Atoms < 200 nk Our group: Precision BEC interferometry. Ultracold Mixtures & Molecules 400 nk 250 nk Recent control of atomic position and momentum. Remove degrees of freedom Manipulate Controllably/usefully introduce complexity Subhadeep Gupta UW NSF-INT Phys REU, 28 th July 2014

3 Quantum Degeneracy in a gas of atoms 1 atom per quantum state N atoms V volume T temperature Number of atoms = (Dx) 3 ~ V (Dp) 3 ~ (m k B T) 3/2 (available position space) (available momentum space) h 3 Quantum Phase Space Density n h 3 ~ 1 (m k B T) 3/2 (n=n/v) Air n ~ /cm 3, T c ~ 1mK Stuff n ~ /cm 3, T c ~ 0.1K Everything (except He) is solid Dilute metastable gases n ~ /cm 3 T c ~ 1mK!! Ultracold!! and ~ non-interacting

4 Bose-Einstein Condensation (BEC) N db atoms 2 V volume T temperature h mk T n 3 B db << 1 3 n db ~ 1 n N V Quantum Phase Space Density 3 n db >> 1

5 Laser cooling Evaporative cooling Relevant Ultracold Temperatures on the Log Kelvin Scale Depth of atom traps atomic interactions (late 80 s, Nobel 97) s u r f a c e o f s u n r o o m t e m p. l i q u i d Nitrogen BCS superconductors, 4 He superfluid, CMB fractional quantum hall effect s u p e r f l u i d 3 H e d i l u t e B p-wave threshold ( db ~ R ~ few nm) (95, Nobel 01) Degenerate Gas ( db ~ n -1/3 ~ few x 100nm) Zero point energy

6 Some major achievements in ultracold atomic physics Bose-Einstein condensation (95: JILA, MIT, Rice.) Macroscopic coherence (97: MIT, ) Superfluidity, Vortex lattice Superfluid to Mott-insulator quantum phase transition (02: Munich,..) Degenerate Fermi gas (99: JILA, Rice, ENS, Duke, MIT, Innsbruck,.)

7 COLDER Ultracold Climate Control 2x Yb atoms

8 Knobs for Quantum Engineering Using e-m fields, can control (relatively) easily Temperature & density Dimensionality Crystal structure lattices Magnetization Magnitude & sign of the charge Chemical structure form molecules HIGH LOW

9 Population Fraction -6 ћk Precision BEC Interferometry Optical Standing Wave Diffraction -4ћk -2 ћk +2 ћk +4 ћk Optical Pulse Strength +6 ћk Lots more light

10 Precision Measurements of the fine structure constant, a (Fig. from Gabrielse, 2009) g/2: a from measurement of electron magnetic moment and QED theory Rb, Cs: Atomic Physics route to a. (Also new 2011 measurement in Rb) Our Yb BEC route to a: Targeted at 0.1 ppb.

11 Atomic Physics Route to a, test of QED ppb: hydrogen spectroscopy (Udem et al.,1997; Schwob et al.,1999) ~ 0.1 ppb: penning trap mass spectr. (Bradley et al.,1999, Ed Myers 2012) e 2R h 2R a c c m e c M M e h m 0.4 ppb: penning trap mass spectr. (Beier et al., 2002) rec 1 2 m k 2 Photon Recoil Measurement using Atomic Interferometry

12 Contrast Interferometer with Yb BEC Contrast Signal T=11ms 34ms period

13 Contrast Interferometer with Yb BEC Symmetric geometry and highly coherent source 8N T 2 rec rec T Resolving interaction and diffraction shifts at few ppm Will install acceleration pulses for sub-ppb Contrast Signal T=11ms 34ms period

14 Interferometric Probe of Phase Transition Absorption Images Contrast Signals 34ms period

15 Mixtures Spin Mixture Same species Eg. Realization of fermion pairing Elemental Mixtures Different species Differences in mass, valence Fermi/Bose Species/selective tools Bath or Probe Ultracold Polar molecules

16 Ultracold Polar Molecules Long-range interactions (1/r 3 vs 1/r 6 ) Precision Spectroscopies for m p /m e time variation _ + Candidate for scale-able quantum information processing Controlled ultracold chemical reactions

17 Quantum Degenerate Li-Yb mixture 6 Li T = 0.3 T F TOF = 0.5 ms 174 Yb BEC TOF = 10ms Extract a = (13 3) a 0 (~ 0.7nm) V. Ivanov et al. PRL 106, (2011) A. Hansen et al. PRA 84, (R) (2011)

18 Quantum Degenerate Li-Yb mixture 6 Li T = 0.3 T F TOF = 0.5 ms <0.1 T F with further cooling 174 Yb BEC TOF = 10ms A. Hansen et al. PRA 87, (2013)

19 Energy Feshbach Resonance: Knob for Strong Interactions and Ultracold Molecules a < 0 Closed Channel (molecular potential) Open Channel (incoming particles) Internuclear Distance a tuned by external magnetic field For large a > 0, Feshbach molecule binding energy e B 2 2 ma

20 Feshbach Resonance in Lithium Real part a 21 (a 0 ) Feshbach Resonance betw 2 spins of 6 Li Magnetic field [Gauss] Fermi gas physics; High Tc Fermi superfluid; BEC/BCS crossover; Unitary fermions; Universal few-body physics.

21 Yb + Feshbach resonant Li a/1000a 0 A. Khramov et al, PRA 86, (2012)

22 Photoassociation Resonance Scan

23 Laser Cooling z I s- s- P x s+ s+ s- y I s+ S Magneto-Optical Trap (MOT) Workhorse of laser cooling Atom Source ~ 600 K; UHV environment abs em => COOLING! (Need a 2 level system)

24 Magneto-Optical Trapping

25 Evaporative Cooling in a Conservative Trap Lens Optical Dipole Trap L << res Depth ~ Int/D; Heating Rate ~ Int/D 2 mk 2-1/2 V V 0 V pre collision post collision

26 Evaporative Cooling in a Conservative Trap Lens Optical Dipole Trap L << res Depth ~ Int/D; Heating Rate ~ Int/D 2 mk 2-1/2 V V 0 V pre collision post collision

27 Dual Species Apparatus Yb Oven Yb Zeeman Slower Pump Area Main Chamber Li Zeeman Slower Ultrahigh Vacuum (UHV < Torr) Li Oven

28 Apparatus I

29 Ultracold Atoms and Molecules Group AFOSR Army: MURI

30 Anders Hansen, Alex Khramov, Alan Jamison, Will Dowd, Ben Plotkin-Swing, Ricky Roy, Alaina Green, Katie MacAlpine, Dan Gochnauer, Frank Munchow, Kalista Smith, Lee Willcockson Raj Shrestha, Anupriya Jayakumar, Vlad Ivanov Stephen Di Iorio, Chow Yi Chao, Brendan Saxberg, Dan Gochnauer, Ben Schwyn, Charlie Fieseler, Jiawen Pi, Eric Lee-Wong, Jason Grad, Dane Odekirk, Ryan Weh, Billy English, Ryne Saxe, Carson Teale, N. Maloney AFOSR Army: MURI