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Updated: Mar 24, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Certifying the Presence of a Photonic Qubit by Splitting It in Two
Evan Meyer-Scott1, Daniel McCloskey1, Klaudia Gołos1
1Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, 200 University Ave W, Waterloo, Ontario, Canada N2L 3G1.
Abstract:
We present an implementation of photonic qubit precertification that performs the delicate task of detecting the presence of a flying photon without destroying its qubit state, allowing loss-sensitive quantum cryptography and tests of nonlocality even over long distance. By splitting an incoming single photon in two via parametric down-conversion, we herald the photon's arrival from an independent photon source while preserving its quantum information with up to (92.3±0.6)% fidelity. With reduced detector dark counts, precertification will be immediately useful in quantum communication.
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