What can we do with a quantum degenerate mixture ? v = 41, J = 1 - - PowerPoint PPT Presentation

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What can we do with a quantum degenerate mixture ? v = 41, J = 1 - - PowerPoint PPT Presentation

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Nambu Symposium @OCU, Dec. 13, 2018 What can we do with a quantum degenerate mixture ? v = 41, J = 1 Shin Inouye (3) 1 S + Osaka City University 875nm 641nm v = 91, J = 0 X 1 S + v = 0, J=0 X 1 S + Ion counts [arb.units] 3.0 2.0 1.0

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3.0 2.0 1.0 0.0 Ion counts [arb.units] 15 10 5

  • 5

Time [µs]

v = 0, J=0 X1S+ 641nm v = 41, J = 1 (3)1S+ 875nm v = 91, J = 0 X1S+

Shin Inouye Osaka City University

Nambu Symposium @OCU, Dec. 13, 2018

What can we do with a quantum degenerate mixture ?

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Outline How to cool atoms Properties of BEC Tuning interactions (Feshbach resonance) Cold molecules Conclusion and Outlook

Nambu Symposium @OCU, Dec. 13, 2018

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Everybody loves to cool liquids ... but, we are interested in cooling gases!

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“Ideal system” to study Condensed Matter Physics!

Significance of cold atom research

Awarded in 2001 Cornell, Ketterle, Wieman

Anderson et al., Science, 269 198 (1995)

Produced in 1995

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phys.org March 3, 2017

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SLIDE 7

Bosons BEC

phase transition at TC

Fermions Fermi sea of atoms

gradually emerges for T<TF

E

F

Further lower temperature

What is ultracold quantum gas?

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SLIDE 8

Problem with gases: Typical Tc is quite low

0. 000 000 1K = 100nK

300K "Tokyo" Tc < 1mm

Tc = h2 2πmkB n 2.612 ! " # $ % &

2/3

absolute zero ”Osaka"

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SLIDE 9

Laser cooling

? ?

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laser cooling evaporative cooling

(MOT)

300 K to 1 mK 1 mK to 100 nK

(Magnetic trap)

Technological breakthroughs

  • > lowest man-made temperature
  • A. E. Leanhardt, T. A. Pasquini, M. Saba, A. Schirotzek, Y. Shin, D. Kielpinski, D. E. Pritchard, and W. Ketterle:

Adiabatic and Evaporative Cooling of Bose-Einstein condensates below 500 Picokelvin. Science 301, 1513-1515 (2003).

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SLIDE 11

Evaporative cooling

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Bose-Eintein condensation

Time-of-flight Release atoms from the trap, wait for tens of milli-seconds, and take shadow picture.

Anderson et al., Science, 269 198 (1995)

Suddenly momentum distribution becomes narrower. ↓ Bose-Einstein Condensation!

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Outline How to cool atoms Properties of BEC Tuning interactions (Feshbach resonance) Cold molecules Conclusion and Outlook

Nambu Symposium @OCU, Dec. 13, 2018

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  • Density: ~ 1014 cm-3
  • Temperature: < 100 nK
  • Number of atoms: < 107
  • Size: 20X20X200 µm
  • Life time> 10 s
  • Atomic speciesRb, Na, Li, …

Properties of a BEC

  • gaseous superfluid
  • macroscopic wavefunction

(Quantum depletion: alkali BEC < 1%, liq. He >90%)

Typical parameters

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SLIDE 15

What we are looking at?

It is useful to introduce y(r)

Kinetic energy Confining potential Interaction between atoms

c-number quantum fluctuation

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Hamiltonian is unchanged under global gauge transformation:

Nambu-Goldstone mode: phonon Order parameter and Spontaneous Symmetry Breaking

y(r) satisfies Penrose-Onsager relation: vanishes as |r-r'|→∞

w k

phonon (~k) particle (~k2)

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Direct confirmation of macroscopic wavefunction? Classical mechanics Quantum mechanics Interference!

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  • M. R. Andrews et al., Science 275, 637 (1997)

|y1(r,t=0)|2 |y2(r,t=0)|2 |y1( r, t = T ) + y2( r, t = T ) |2

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Measurement of 1st-order spatial coherence

Extract matterwave from two separated points and make them interfere.

  • I. Bloch, T. W. Hänsch & T. Esslinger

Nature 403, 166–170 (2000)

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Vortex !

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  • K. W. Madison, F. Chevy, W. Wohlleben*, and J. Dalibard
  • Phys. Rev. Lett. 84, 806–809 (2000)

Vortex Formation in a Stirred Bose-Einstein Condensate

Rotate a BEC with a laser beam

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J.R. Abo-Shaeer, C. Raman, J.M. Vogels, and W. Ketterle: Observation of Vortex Lattices in Bose-Einstein Condensates. Science 292, 476-479 (2001).

Vortex lattice !

Abrikosov lattice

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sweeping a laser beam to generate vortex!

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(wavefronts of matterwaves realeased from two BECs)

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BEC with a vortex

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"Observation of vortex phase singularities in Bose-Einstein condensates."

  • S. Inouye et al., PRL, 87, 080402 (2001).

Interferometric detection of vortex pair

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Outline How to cool atoms Properties of BEC Tuning interactions (Feshbach resonance) Cold molecules Conclusion and Outlook

Nambu Symposium @OCU, Dec. 13, 2018

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Kinetic energy Confining potential Interaction between atoms

Can we tune the scattering length?

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colliding atoms

Tuning the interaction (Feshbach resonance)

Herman Feshbach

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Use nuclear spin

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Interference!

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"Observation of Feshbach resonances in a Bose-Einstein condensate."

  • S. Inouye et al., Nature 392, 151 (1998).

“U” is modified by factor of 20

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“U” is modified by seven orders of magnitude

"Extreme Tunability of Interactions in a 7Li Bose-Einstein Condensate“

  • S. E. Pollack, D. Dries, M. Junker, Y. P. Chen, T. A. Corcovilos, and R. G. Hulet,

Physical Review Letters 102, 090402 (2009).

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"Extreme Tunability of Interactions in a 7Li Bose-Einstein Condensate“

  • S. E. Pollack, D. Dries, M. Junker, Y. P. Chen, T. A. Corcovilos, and R. G. Hulet,

Physical Review Letters 102, 090402 (2009).

( ) ( ) ( )

r r m a r V m t r i

trap

y y p y ÷ ÷ ø ö ç ç è æ + + Ñ

  • =

¶ ¶

2 2 2 2

4 ) ( 2 ! ! !

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Outline How to cool atoms Properties of BEC Tuning interactions (Feshbach resonance) Cold molecules Conclusion and Outlook

Nambu Symposium @OCU, Dec. 13, 2018

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What can we do with two BECs?

41K 87Rb

Make molecules!?

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Blatt & Wineland, Nature 453 1008 (2008) Anderson et al., Science, 269 198 (1995)

Cold ions (trapped ions) Cold atoms Cold molecules?

Frequency standards Quantum Information Bose Condensation Strongly correlated gas Frequency standards

“New Frontier”

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“Indirect” method (2005~)

degenerate mixture Feshbach molecule (d:small) ground state (d: large) Feshbach resonance T~100nK (Still Quantum Degenerate)

Most difficult?

T~100nK

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SLIDE 40

STIRAP

No heating: 100nK out of 6000K will kill the sample!

100nK 6000 K

*Stimulated Raman Adiabatic Passage Find the right excited state Stabilize two laser frequencies in ~10-10 level (i.e. ~kHz level ) slowly

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v = 0, J=0 X1S+ 641nm v = 41, J = 1 (3)1S+ 875nm v = 91, J = 0 X1S+

0.16 0.12 0.08 0.04 0.00 Intensity [arb.units] 15 10 5

  • 5

Time [µs] 641nm pulse 875nm pulse 3.0 2.0 1.0 0.0 Ion counts [arb.units] 15 10 5

  • 5

Time [µs]

Achieving rovibrational ground state

  • K. Aikawa et al.,

PRL 105, 203001 (2010)

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There is a good news and bad news...

  • -- Good news is we produced ultracold

groundstate polar molecules!

  • -- Bad news is the density is really really low!
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Ultracold KRb molecules imaged by direct absorption D.S. Jin and J. Ye, Physics Today, May 2011

Ultracold polar molecules near degeneracy (by JILA)

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K.-K. Ni et al., Nature 464, 1324 (2010) same internal states AND dipoles aligned by an external field m=+1/2 1/2 Electric field (~kV/cm)

Directional chemistry (JILA)

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Measure time variation of fundamental constants!

  • accelerating expansion of universe
  • Cosmic Microwave Background
  • Large scale structure

Possible extensions to the L-CDM 1836 1 » =

p e

m m µ

c e !

2

4 1 pe a =

P

g

, etc. Quintessence →Fluctuation of fundamental constants??

45

We focused on electron-to-proton mass ratio µ General relativity + L-CDM model is successful in explaining following phenomena: However, origin of dark energy (and dark matter) is not understood.

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The limit of time variation of me/Mp(≡µ)

Radio-astronomical observations

7

10 ) . 1 . ( /

  • ´

± = D µ µ

Alcohol in the early universe (J. Bagdonaite et al, Science 339, 46 (2013)) (in 7109 years)

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SLIDE 47

The limit of time variation of me/Mp(≡µ)

Laboratory observations

year / 10 ) 6 . 5 8 . 3 ( /

14

  • ´

± = µ µ !

molecular spectroscopy of SF6

  • A. Shelkovnikov et al, PRL 100, 150801 (2008)

Optical Fiber link (~43km) Cs Fountain SYRTE frequency comb

+

rovibrational transition in SF6

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Why molecule?

Large m Small m

δE E = 1 2 δm m

Frequencies are directly related to the inertial mass of nucleus.

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FWHM50Hz

Ultracold molecule is ideal for precision spectroscopy!

634 963 783.4580.093 Hz Average of 5000 sweeps (6 hours) 634 963 781.5640.094 Hz Zeeman shift compensation S/N ~ 500 (c.f. Number of molecules used ~ 106)

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Calibration of the magnetic field

F = 0 F = 1 mF = 1 mF = 0 mF = 0

2.4 s 2.4 s 2.4 s 2.4 s

  • mF = 0

mF = 1 mF = 0 mF = 1 Time

Time (hour) Magnetic Field (mG)

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Good News: we broke the world record set by SF6!

  • A. Shelkovnikov et al.,

PRL 100, 150801(2008)

1 µ ∂µ ∂t = 3.8± 5.6

( )×10−14 / year

1 µ ∂µ ∂t = 0.30 ±1.00Stat ± 0.16Sys

( )×10−14 / year

Factor of five improvement

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  • J. Kobayashi, A. Ogino, and SI
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Francesca Ferlaino and Rudolf Grimm, Physics 3, 9 (2010).

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What can we do with two BECs?

41K 87Rb

Phase separation!?

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36μm x 208μm(1pix.=2.6μm)

Phase separation after quenching the interaction

1D 2D

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Digital Mirror Device Holographically generated ring beam

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3.0 2.0 1.0 0.0 Ion counts [arb.units] 15 10 5

  • 5

Time [µs]

v = 0, J=0 X1S+ 641nm v = 41, J = 1 (3)1S+ 875nm v = 91, J = 0 X1S+

Conclusion

Cold atom is a versatile ground both for condensed matter physics precision measurement

... please stay tuned