Single Atoms in Rotating Ring Optical Lattices

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Single Atoms in Rotating Ring Optical Lattices
KITPC Condensed Matter Physics of Cold Atoms
---- Optical Lattices II
Mingsheng ZHAN (???) State Key Lab of
Magnetic Resonance and Atomic and Molecular
Physics, Wuhan Institute of Physics and
Mathematics, CAS Center for Cold Atom Physics,
CAS
Oct 15, 2009 Beijing
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Motivation

• quantum simulation
• quantum computing
• single photon source
• single atom physics

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quantum simulation ?? mimic an unknown
system using a controllable
system
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Hubbard model
John C. Hubbard at 1963
J tunneling U in site interaction
external potential

• Approximate model that describes electrons in
  solids
• Hamiltonian describes fermions /bosons in a
  periodic potential
• Simple, yet hard to solve analytically,
  numerically or empirically

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Quantum logic gates

• Need of experimental aspects
• single atoms
• cooled to ground state
• double-well
• readout

U.Dorner, T.Calarco, P.Zoller, A. Browaeys and P.
Grangier, J. Opt. B Quantum Semiclass. Opt. 7
(2005) S341S346
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Atom array by dipole trap (bottom-up)
Ultracold atoms in lattices (top-down)
single atom dipole trap array cooling the
array
ultracold gas optical lattices addressing
individual atoms
The same goal by different routes (????) (for
quantum simulation)
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Optical Dipole Trap for Atoms
Atom
Laser
Cylindrically symmetric harmonic oscillator
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Superfluidity limit
Good phase ?i, but Poissonic number
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Mott Insulator State
Fock state




good number, But no phase
M. Greiner, O. Mandel, T. Esslinger, T. Hansch,
I. Bloch, Nature 415 (2002) 39.
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P.Grangiers group IO/CNRS
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"Collision blockade
RE Radiative Escape process FCC
Fine-structure Changing Collision
Phys. Rev. Lett. 89, 023005 (2002)
Nature 411, 1024 (2001).
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D.Meschedes group Bonn Univ.
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The single atom trap _at_ WIPM
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Single Atom Trap _at_ WIPM experimental setup
87Rb MOT 780nm dipole trapping 830/852nm
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Fluorescence of a single Rb atom (2009/02/13)
1 atom
0 atom
? 10s ?
2 atom
1 atom
0 atom
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Hanbury Brown and Twiss (HB-T) effect
classical field non-classical thermal
coherent single photon
Fluorescence of single atom, antibunching
http//en.wikipedia.org/wiki/Hanbury-Brown_and_Twi
ss_effect M.O.Scully and M.S.Zubairy, Quantum
Optics, CUP 1997, P.307
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Single Atom HBT Experiment
SPCM EGG SPCM-AQRH-14-FC DiscriminatorORTE
C 935(Quad 200-MHz Constant-Fraction
Discriminator) Coincidence RoentDek TDC8HP
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HBT measurement of single atom in dipole trap
18.4mw_at_830nm 2.28mw_at_Cooling 0.80mw_at_Repump
AC shift 39MHz U0 1.9mK Rabi Freq
?0 26.6MHz(RL) 33.7MHz(CL22) 79 MHz(CL23) 107
total events 103 coincidence
Photon antibunching (single atom)
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lifetime of the single atom trap
Time sequence
threshold
Counting
1) once counting gt threshold, freezing the
trap 2) waiting a time ?t, then check
repeat 100 times 3) new ?t, then repeat.
?
?t
?
ON OFF
Cooling and repump laser
50ms
?
ON OFF
MOT magnetic field
?
ON OFF
Counting clock
ON OFF
Dipole trap laser
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Lifetime 468ms with MOT on
Lifetime 11s with MOT off
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Ring Optical Latticesby SLM
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Laguerre-Gaussian Mode
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Ring Optical Lattice (ROL)

• Superposition of the mode

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Realizing ROLwith a spatial light modulator
(SLM)
SLM
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0th order
1th order modulated
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Trapping atom array with ROL
Single trap
Double trap
Spatial filter
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Rotating the ROL
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Rotating ROL
Scheme 1 max 60Hz
Continuous phase pattern animation on the SLM,
max refresh rate 60Hz
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Scheme 2 up to MHz (EOM driven phase
change)
2Hz rotation is shown here
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single atoms in rotating ROL
Rotating ROL _at_12Hz with 1 atom
Rotating ROL _at_6Hz with 2 atoms
Xiaodong He, Peng Xu, Jin Wang and Mingsheng
Zhan, Opt.Express (accpted, 2009)
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Dynamics of single atoms in the traps
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Loading two atoms to a trap
Ring trap
Gaussian trap
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Light assisted nonelastic collisions of two
atoms in a trap
In a Ring trap
Collisions rare Difficult to meet
2 atoms remain
In a Gaussian trap
0 atom
Collisions rich Easier to meet
1 atom
MOT light on
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Splitting a trap (with an atom) to two traps
or
Potential or force? (single vs multi
collision) Particle or wave packet? (single atom
interferometer)
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Figure 12. Axial insertion. An atom trapped in
one of the potential wells of the standing wave
of theVDT is inserted into the Gaussian potential
well of the HDT by axially moving the VDT along
the z-direction.
Figure 13. Radial insertion of an atom. (a) An
atom in the VDT after the extraction. The traps
are separated by displacing the HDT along the
x-direction. (b) The atom in the VDT is
transported to the z-position of the HDT. (c)
The traps are merged by moving the HDT along the
x-direction towards the VDT. d) Evolution of the
radial potentials of the traps along the x-axis
for steps (b) and (c).
Y Miroshnychenko et al., New J. Phys. 8(2006)191
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?
dichroic mirror
Static trap
fluorescence
Moving trap
To SPCM
PZT
PZT scan speed 10um/40ms
160ms
?
?
CoolingRepump
80ms
5V
PZT
?
?
-2V
The depth of the moving well affects the rate
carrying the atom
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Time evolution of the trap intensity profile
Initial
?
The final position of the atom is determined by
force not the depth of potential.
exposure time 1ms readout time 2.5ms
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Atom transfer between traps
Gaussian trap
Merging
Splitting
ring trap
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Time sequence double ? Gaussian ? double
On
Interaction time N1/60 s N 1,2,3 variable
Cooling light repumping light MOT coil
Off
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Time sequence double ? ring ? double
On
Interaction time N1/60 s N 1,2,3 variable
Cooling light repumping light MOT coil L (or
L) SLM light
Off
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Single atom transport(via a Gaussian trap)
1/60 s
3/60 s
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Single atom transport(via a ring trap)
1/60 s
3/60 s
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Next

• cooling atom to ground state internal state
  control
• making interaction of atoms in/between sites
• entanglement, quantum simulation / computing
  
• single atom AI, HBT

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a way to bring the atoms closer optical
vector beam (OVB)
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Optical vector beam(OVB)
Tailoring of arbitrary optical vector beams New
Journal of Physics 9 (2007) 78

• The focused pattern can be much smaller than the
  diffraction limit

Phys. Rev. Lett. 91, 233901 (2003) Phys. Rev.
Lett. 100, 123904 (2008)
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Experimental Arrangement
HW
PW
to trap
PBS
SLM
HW
HW
Dipole trap laser
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Primary results with OVB
OVB trap
Lifetime longer Tighter potential
Normal ring trap
Lifetime shorter
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Acknowledgments
?? ??? ?? ??
Ministry of Sci Tech of China (MOST) Chinese
Academy of Sciences (CAS) Natural Science
Foundation of China (NSFC)
All of you, for your attention!