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Updated: Jan 21, 2026

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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
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High-visibility Franson interference of time-energy entangled photon pairs from warm atomic ensemble
Optics Letters
|August 2, 2019
Summary
Researchers demonstrated nonlocal two-photon interference using entangled photon pairs from warm Rb87 atoms. This experiment confirms entanglement
Area of Science:
- Quantum Optics
- Atomic Physics
- Quantum Information
Background:
- Entanglement is a key quantum phenomenon.
- Franson interference is a test of entanglement.
- Previous experiments faced limitations.
Purpose of the Study:
- To demonstrate Franson interference with time-energy entangled photons.
- To confirm the nonlocal nature of entanglement from a warm atomic ensemble.
- To utilize a cascade-type atomic system for photon pair generation.
Main Methods:
- Generating time-energy entangled photon pairs via collective two-photon coherence.
- Using warm Rb87 atoms in a 5S1/2-5P3/2-5D5/2 transition.
- Employing two spatially separated unbalanced Michelson interferometers.
Main Results:
- Achieved high-visibility Franson interference fringes (99.1±1.3%).
- Observed interference with continuous-wave-mode photon pairs.
- Confirmed nonlocal two-photon interference in separated channels.
Conclusions:
- This is the first demonstration of nonlocal two-photon interference using a cascade-type atomic system.
- The results validate entanglement as a nonlocal property.
- The experiment successfully implemented Franson's original proposal.
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