A Single Photon Source for Photon-atom Interaction

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A Single Photon Source for Photon-atom
Interaction

• Xingxing Xing
• Centre for Quantum
• Info. Quantum Control,
• Dept. of Physics, Univ. of Toronto

CQISC 2006, Calgary
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Group member

• Photonics lab _at_Toronto
• Rob Adamson
• Lynden (Krister) Shalm
• Xingxing Xing
• Dr. An-Ning Zhang
• Prof. Aephraim Steinberg

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Outline

• Why single photon source?
• Why photon-atom interaction?
• How to build up a source?
• What could we use the source for?

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Motivation

• Necessity of a single photon source?
• Investigate non-classical behaviors
• Use in quant logic, quant crypto., etc.

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Motivation

• Photons are ideal carrier for Quantum Info
  Processing and Q. Computation
• easy to generate and manipulate
• stable not interact much with environment
• LOQC scheme could be essential as part of quantum
  computation networks
• Problems
• Photons dont interact much with envi. ? hard for
  storage
• Experience losses during commu. ? reconstruct
  states
• They dont interact with each other either! ?
  two-qubit gates?

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Motivation

• On the other hand, atoms are good for some
  aspects
• They interact strongly with each other
• ? good candidate for two-qubit gates
• Long decoherence time is possible trapping
• ? quantum memory and quantum repeater
• Combination of the two Perfect!

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Methods
Comparison of Different Schemes of Single photon
source
Different Sources Pros Cons
Attenuated laser easy Non-deterministic (Poisson)
Quantum dots Real single semiconductor tech Not feasible for photon-atom interaction
Single atom real single Hard (Kimbles heroic exp.)
Parametric down conversion Triggered deterministic Broadband1013 Hz Atomic 106 Hz
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Methods

• PDC is good, except for the bandwidth
• Make use of cavity confine the spectrum, also
  known as Optical Parametric Oscillator (OPO)

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Doppler-free Saturated Spectroscopy

• Problem narrow linewidth of atoms 6MHz
• Doppler shift
• The frequency of a moving source/observer is
  shifted relative to the observer/source. NOTE
  the real freq. doesnt change!
• For a moving observer
• Vo speed of observer
• positive if the observer is moving away
  from the source
• negative if the observer is moving towards
  the source

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Doppler

• Stationary and moving source

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Doppler effect in photon-atom interaction

• Doppler broadening in absorption profile

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OPO Setup
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Testing of the laser linewidth
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Next step

• Optimize SHG
• Setup OPO cavity and optimize it
• Play with the source

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Potential Applications

• Electromagnetically Induced Transparency (EIT)
• Quantum Memory
• Quantum Repeater
• As a tool to investigate the fundamentals of QM
  through interaction with cold atoms/BEC
• Gap between Classical and quantum world?
• Single photon - single atom?
• For rent a single photon source for free space
  QKD

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EIT

• Group velocity coupling filed
• The state of interaction system photon atom

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Storage through EIT
Fleischhauer, PRL 84, 5094, 2000
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Quantum repeater
L.-M., Duan et.al., 414, 413
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Summary

• A scheme for narrow bandwidth single-photon
  source (triggered deterministic)
• Such photon-atom interaction could help fill the
  gap between LCQO and atomic physics
• Questions? Comments? Suggestions?