We demonstrate photonic quantum circuits that operate at the stringent levels that will be required for future quantum information science and technology. These circuits are fabricated from silica-on-silicon waveguides forming directional couplers and interferometers. While our focus is on the operation of quantum circuits, to test this operation required construction of a spectrally tuned photon source to produce near-identical pairs of photons. We show non-classical interference with two photons and a two-photon entangling logic gate that operate with near-unit fidelity. These results are a significant step towards large-scale operation of photonic quantum circuits.
@article{arxiv.1004.0326,
title = {High-fidelity operation of quantum photonic circuits},
author = {Anthony Laing and Alberto Peruzzo and Alberto Politi and Maria Rodas Verde and Matthaeus Halder and Timothy C. Ralph and Mark G. Thompson and Jeremy L. O'Brien},
journal= {arXiv preprint arXiv:1004.0326},
year = {2011}
}