1. 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

2. 2 Xingxing Xing, U.of Toronto Group member Photonics lab @Toronto  Rob Adamson  Lynden (Krister) Shalm  Xingxing Xing  Dr. An-Ning Zhang  Prof. Aephraim Steinberg

3. CQISC 2006, Calgary3 Xingxing 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?

4. CQISC 2006, Calgary4 Xingxing Xing, U.of Toronto Motivation Necessity of a single photon source?  Investigate non-classical behaviors  Use in quant logic, quant crypto., etc.

5. CQISC 2006, Calgary5 Xingxing 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 computation networks Problems  Photons don’t interact much with envi.  hard for storage  Experience losses during commu.  reconstruct states  They don’t interact with each other either!  two-qubit gates?

6. CQISC 2006, Calgary6 Xingxing 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!

7. CQISC 2006, Calgary7 Xingxing Xing, U.of Toronto Methods Different SourcesProsCons Attenuated lasereasyNon-deterministic (Poisson) Quantum dotsReal single; semiconductor tech Not feasible for photon-atom interaction Single atomreal single;Hard (Kimble’s heroic exp.) Parametric down conversion Triggered deterministic Broadband:10 13 Hz Atomic: 10 6 Hz Comparison of Different Schemes of Single photon source

8. CQISC 2006, Calgary8 Xingxing Xing, U.of Toronto Methods PDC is good, except for the bandwidth Make use of cavity: confine the spectrum, also known as Optical Parametric Oscillator (OPO)

9. CQISC 2006, Calgary9 Xingxing Xing, U.of Toronto 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

10. CQISC 2006, Calgary10 Xingxing Xing, U.of Toronto Doppler Stationary and moving source

11. CQISC 2006, Calgary11 Xingxing Xing, U.of Toronto Doppler effect in photon-atom interaction Doppler broadening in absorption profile

12. CQISC 2006, Calgary12 Xingxing Xing, U.of Toronto OPO Setup

13. CQISC 2006, Calgary13 Xingxing Xing, U.of Toronto Testing of the laser linewidth

14. CQISC 2006, Calgary14 Xingxing Xing, U.of Toronto Next step… Optimize SHG Setup OPO cavity and optimize it Play with the source…

15. CQISC 2006, Calgary15 Xingxing Xing, U.of Toronto 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…

16. CQISC 2006, Calgary16 Xingxing Xing, U.of Toronto EIT Group velocity & coupling filed The state of interaction system: photon + atom:

17. CQISC 2006, Calgary17 Xingxing Xing, U.of Toronto Storage through EIT Fleischhauer, PRL 84, 5094, 2000

18. CQISC 2006, Calgary18 Xingxing Xing, U.of Toronto Quantum repeater L.-M., Duan et.al., 414, 413

19. CQISC 2006, Calgary19 Xingxing Xing, U.of Toronto 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?