Multiplexed single photon source using one-way switching elements

Abstract

A multiplexed single photon source for quasi-deterministically generating single photons, wherein heralded random single photons generated by pulsed random single photon source are sent through a series of optical switches each having first and second input and output modes and each capable of being switched from a first state corresponding to a SWAP operation to a second state corresponding to an Identity operation on the mode space, whereby the first and second input and output modes of the switches are connected in series to form a first and second optical path respectively, and whereby a first output mode of a last optical switch forms the output mode of the multiplexed single photon source and a second output mode of the last optical switch is connected by a delay loop introducing a time delay Tto the second input mode of a first optical switch. It furthermore relates to a method of quasi-deterministically generating single photons with such a multiplexed single photon source, the method comprising initializing, before or at the start of a first cycle, the first switch in the first state and all subsequent switches in the second state; switching, when the generation of a random single photon is heralded, the first switch to the second state after that photon has been routed onto the closed optical path formed by the second optical path and the delay loop, thereby ensuring that the photon may loop around the closed optical path; and, switching, at the start of the Nth cycle, a last switch of the series of optical switches into the first state, thereby causing the photon to be routed out of the closed optical path and into the output mode of the multiplexed single photon source, such that the photon is output quasi-deterministically at a time N Td after the start of the first cycle.