A Single Photon Source for

Photon-atom InteractionXingxing XingCentre for Quantum Info. & Quantum Control, Dept. of Physics, Univ. of Toronto

CQISC 2006, Calgary

CQISC 2006, Calgary 2Xingxing Xing, U.of Toronto

Group member

Photonics lab @Toronto

Rob Adamson

Lynden (Krister) Shalm

Xingxing Xing

Dr. An-Ning Zhang

Prof. Aephraim Steinberg

CQISC 2006, Calgary 3Xingxing Xing, U.of Toronto

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.

CQISC 2006, Calgary 5Xingxing Xing, U.of Toronto

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 computatio

n networks

Problems Photons don’t interact much with envi. hard for storage Experience losses during commu. reconstruct s

tates They don’t interact with each other either! two-qubit gat

es?

CQISC 2006, Calgary 6Xingxing Xing, U.of Toronto

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!

CQISC 2006, Calgary 7Xingxing Xing, U.of Toronto

Methods

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 (Kimble’s heroic exp.)

Parametric down conversion

Triggered deterministic

Broadband:1013 Hz

Atomic: 106 Hz

Comparison of Different Schemes of Single photon source

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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. doesn’t 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

v

vff 0

0 1

CQISC 2006, Calgary 10Xingxing Xing, U.of Toronto

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…

CQISC 2006, Calgary 16Xingxing Xing, U.of Toronto

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?