We report a proof-of-principle demonstration of a probabilistic controlled-NOT gate for single photons. Single-photon control and target qubits were mixed with a single ancilla photon in a device constructed using only linear optical elements. The successful operation of the controlled-NOT gate relied on post-selected three-photon interference effects which required the detection of the photons in the output modes.
@article{arxiv.quant-ph/0303095,
title = {Experimental Controlled-NOT Logic Gate for Single Photons in the Coincidence Basis},
author = {T. B. Pittman and M. J. Fitch and B. C Jacobs and J. D. Franson},
journal= {arXiv preprint arXiv:quant-ph/0303095},
year = {2009}
}