Certifying the Presence of a Photonic Qubit by Splitting It in Two
Evan Meyer-Scott, Daniel J. McCloskey, Klaudia Gołos, Jeff Z. Salvail, Kent Bonsma-Fisher, Deny R. Hamel, Adán Cabello, Kevin J. Resch, Thomas D. Jennewein · Physical Review Letters · 2016
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.