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Wave Packet Echo in Optical Lattice and Decoherence Time

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Generator. AOM1. TUI. PBS. AOM2. Amplifier. PBS. PBS. Spatial filter ... Anatomy of an Echo. original oscillation. oscillation from echo pulse. the echo itself ... – PowerPoint PPT presentation

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Title: Wave Packet Echo in Optical Lattice and Decoherence Time


1
Wave Packet Echo in Optical Lattice and
Decoherence Time
  • Chao Zhuang
  • U(t)
  • Aug. 15, 2006
  • CQISC2006

University of Toronto
2
Aephraim Steinberg Matthew Partlow Samansa
Maneshi Jalani Kanem
Department of Physics, Center for Quantum
Information and Quantum Control, Institute for
Optical Sciences University of Toronto
3
Outline
  • Pulse echo
  • Two level system
  • Life time T1, T2, T2
  • How it works in What system
  • Wave packet echo in optical lattice
  • Setup and Measurement
  • Optimize echo pulse
  • Decoherence and coherence control

4
Something General
T1 longitudinal lifetime De-population
T2 transverse homogeneous lifetime De-coherence
T2 transverse inhomogeneous lifetime De-phase
5
Pulse echo How it works
6
Pulse echo Timeline
7
Pulse echo Why its important
  • Inhomogeneous decay due to dephasing can be
    reversed!
  • (De)coherence time due to homogeneous decay can
    be measured directly.
  • Coherence time decides how long quantum
    information can be stored in a quantum system.

8
Pulse echo What system
  • Spin Echo
  • Nuclear Magnetic Resonance
  • E. L. Hahn, Phys. Rev. 80, 580 (1950)
  • Photon Echo
  • Optical Resonance
  • N. A. Kurnit, I. D. Abella, and S. R. Hartmann,
    Phys. Rev. Lett. 13, 567 (1964)
  • Wave Packet Echo
  • F. B. J. Buchkremer, R. Dumke, H. Levsen, G.
    Birkl, and W. Ertmer, Phys. Rev. Lett. 85, 3121
    (2000)

9
Optical Lattice
Wave Packet
Optical lattices are periodic potentials formed
by the ac Stark shift (light shift) seen by atoms
when they interact with a set of interfering
laser beams.
I. H. Deutsch and P. S. Jessen, Phys. Rev. A 57,
1972(1998).
Motional atoms in optical lattice
Motional wave packets in optical lattice
10
Experimental Setup Vertical Optical Lattice
11
Measuring State Population
12
Measuring Coherence Oscillations in the Lattice
dephasing due to lattice depth inhomogeneities
T2
13
Anatomy of an Echo
original oscillation
oscillation from echo pulse
the echo itself
Dephasing due to primarily lattice inhomogeneities
14
Echo in the Lattice (using lattice shifts and
delays as coupling pulses)
max. 13
t
15
Preliminary data on Coherence time in 1D and 3D
Lattice
  • Decoherence due to
  • transverse motion of atoms

inter-well tunneling,
16
2D Fourier Spectroscopy
17
Initial Results
drive freq. Hz
observed oscillation freq. Hz
driven monochromatically with 10 cycles
18
What if we try bang-bang?
(Repeat pulses before the bath gets amnesia
trade-off since each pulse is imperfect.)
19
bang-bang pulse sequences...Some coherence out
to gt 3 ms now...
20
Summary
  • Optimisation of certain class of echo pulses
  • Preliminary work on 3D lattice
  • Preliminary work on characterization of
    frequency
  • response of the system due to Quasi-monochromatic
    excitation
  • Observation of higher-order Echoes
  • Future work
  • Characterize homogeneous and inhomogeneous
  • broadening through 2D FT spectroscopy
  • Design adiabatic pulses for inversion of
    states
  • Study decoherence due to tunneling
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