A strong limitation of linear optical quantum computing is the probabilistic operation of two-quantum bit gates based on the coalescence of indistinguishable photons. A route to deterministic operation is to exploit the single-photon nonlinearity of an atomic transition. Through engineering of the atom-photon interaction, phase shifters, photon filters and photon- photon gates have been demonstrated with natural atoms. Proofs of concept have been reported with semiconductor quantum dots, yet limited by inefficient atom-photon interfaces and dephasing. Here we report on a highly efficient single-photon filter based on a large optical non-linearity at the single photon level, in a near-optimal quantum-dot cavity interface. When probed with coherent light wavepackets, the device shows a record nonlinearity threshold around 0.3±0.1 incident photons. We demonstrate that directly reflected pulses consist of 80% single-photon Fock state and that the two- and three-photon components are strongly suppressed compared to the single-photon one.
@article{arxiv.1607.05977,
title = {A solid-state single-photon filter},
author = {L. de Santis and C. Antón and B. Reznychenko and N. Somaschi and G. Coppola and J. Senellart and C. Gómez and A. Lemaître and I. Sagnes and A. G. White and L. Lanco and A. Auffeves and P. Senellart},
journal= {arXiv preprint arXiv:1607.05977},
year = {2017}
}