Low-light-level photon switching by quantum interference
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Updated: Feb 10, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Yong-Fan Chen1, Zen-Hsiang Tsai, Yu-Chen Liu
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Abstract:
We report an experimental demonstration of low-light-level photon switching by quantum interference in laser-cooled 87Rb atoms. A resonant probe pulse with an energy per unit area of one photon per lambda2/2pi propagates through the optically thick atoms. Its energy transmittance is greater than 63%, or a loss of less than e(-1), because of the effect of electromagnetically induced transparency. In the presence of a switching pulse with an energy per unit area of 1.4 photons per lambda2/2pi, the energy transmittance of the same probe pulse becomes less than 37%, or e(-1). This substantial reduction of probe transmittance caused by switching photons may lead to potential applications in single-photon-level nonlinear optics and manipulation of quantum information.
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