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

We show that the noise threshold for optical quantum computing can be significantly improved by using the EPR-type of photon source. In this implementation, the detector efficiency ${\eta }_d$ is required to be larger than 50%, and the source efficiency ${\eta }_s$ can be an arbitrarily small positive number. This threshold compares favorably with the implementation using the single-photon source, where one requires the combined efficiency ${\eta }_d{\eta }_s>2\mathrm{/}3$. We discuss several physical setups for realization of the required EPR photon source, including the photon emitter from a single-atom cavity.