Improving noise threshold for optical quantum computing with the EPR photon source

We show that the noise threshold for optical quantum computing obtained by Varnava et al. [Phys. Rev. Lett. 100, 060502 (2008)] can be significantly improved by replacing the single-photon source with the Einstein-Podolsky-Rosen (EPR) type of photon source. In this implementation, for an EPR source that emits either nothing (a vacuum state) or a perfect EPR state with probability ηs, the detector efficiency ηd is required to be larger than 50% and the source efficiency ηs can be an arbitrarily small positive number. We also present the error threshold for a more general noise model including additional photon absorption and show that the threshold still compares favorably with the previous results. We discuss several physical setups for realization of the required EPR photon source, including a photon emitter in a single-atom cavity.