1. Study of Quantum Interference Phenomena in Cold Atoms
— from Reduction of the Light Speed
to Quantum Entanglement
余怡德
清華大學物理系
陳應誠 廖彥安
林重維 陳韻文 蘇蓉容 邱馨瑩 潘冠錡
陳泳帆 蔡仁祥 楊致芸 劉昱辰
陳德鴻

4. Measure Light Speed in a Medium
Detector
Laser t
Detector
Laser
t + td
atoms l
v  l / td

6. Chromatic dispersion

7. The index refraction of fused quartz.

8. Electromagnetically Induced Transparency (EIT)
The Phenomenon of
Electromagnetically Induced Transparency (EIT)
probe laser
coupling laser
atoms

9. Quantum Interference + + + ....... = ....... .......
|3
Coupling
|2 = + + +
Probe
|1
path i
path ii
path iii
Transition amplitudes: Ai
Aii
Aiii
Transition probability of |1  |2 = | Ai + Aii + Aiii |2
EIT is the destructive interference between Ai , Aii , Aiii ,
 The probe absorption is suppressed.

10. Experimental Setup |g1 |g2 |e Coupling Laser Probe PD T z y x
AOM
Quadrupole Magnet
T: trapping beam

11. Experimental Spectrum without the Coupling Laser

12. Experimental Spectrum in the Presence of the Coupling Laser

13. Ultrahigh Contrast near the Resonance

14. Group Velocity Predicted from the Experimental Data
吸收率 色散
折射率

15. Photon Switching by Quantum Interference
Probe
|1
|2
|3
|4
Coupling
Switching

16. The Three-Fold Entangled State
|1
|2
|3
|4
Coupling
Switching
Probe
50/50 BS
where 1 or 0 in the | s, | p, and | f denotes presence or absence of the switching, probe, and fluorescence photons measured by the detectors.
Requirements: OD  10 and   10-3.

17. Einstein-Podolsky-Rosen (EPR) Paradox
QM:

18. Information Propagation Cannot Exceed c1 S N
Stern-Gerlach at t1
Stern-Gerlach at t2 L 2

19. Quantum Non-locality
Down-conversion by a BBO crystal to generate two entangled photons
along the intersecting directions of the cones.

20. Teleportation
public communication
EPR
Source
Bob
Alice
secure channel

21. Information Encoding and Decoding  1 R x
Bob
Alice
EPR1:
EPR2:
Information: