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New high-efficiency source of photon pairs for engineering quantum entanglement
1Institute of Physics, University of Tokyo at Komaba, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Physical Review Letters
|June 21, 2001
Summary
Researchers created a photon pair source for quantum experiments. High-visibility interference was observed when the time window was smaller than the path difference, demonstrating quantum entanglement.
Area of Science:
- Quantum optics
- Experimental physics
Background:
- Two-photon interference experiments are crucial for understanding quantum mechanics.
- Previous studies have explored photon pair generation and interference, but controlling the temporal dynamics remains key.
Purpose of the Study:
- To construct an efficient source of photon pairs using a waveguide-type nonlinear device.
- To perform and analyze a two-photon interference experiment using an unbalanced Michelson interferometer.
Main Methods:
- Utilized a waveguide-type nonlinear device for efficient photon pair generation.
- Employed an unbalanced Michelson interferometer with arms of differing lengths.
- Investigated the impact of arrival time difference (Delta L/c) and coincidence counter time window (Delta T) on interference visibility.
Main Results:
- Achieved high-visibility interference fringes (80% +/- 10%) under specific temporal conditions.
- Observed that high visibility occurs when Delta T < Delta L/c.
- Demonstrated that these results are explicable solely through quantum theory.
Conclusions:
- The experiment provides clear evidence for quantum entanglement of optical paths within the interferometer.
- The findings highlight the critical role of temporal parameters in distinguishing classical and quantum interference regimes.