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Updated: Jun 22, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Quantum state tomography of a fiber-based source of polarization-entangled photon pairs
J Fan1, M D Eisaman, A Migdall
1Optical Technology Division, National Institute of Standards and Technology,100 Bureau Drive, Mail Stop 8441, Gaithersburg, MD 20899-844, USA. Jfan@nist.gov
Abstract:
We report an experimental demonstration of a bright high-fidelity single-mode-optical-fiber source of polarization-entangled photon pairs. The source takes advantage of single-mode fiber optics, highly nonlinear microstructure fiber, judicious phase-matching, and the inherent stability provided by a Sagnac interferometer. With a modest average pump power (300 microW), we create all four Bell states with a detected two-photon coincidence rate of 7 kHz per bandwidth of 0.9 nm, in a spectral range of more than 20 nm. To characterize the purity of the states produced by this source, we use quantum-state tomography to reconstruct the corresponding density matrices, with fidelities of 95 % or more for each Bell state.
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