Frequency-multiplexed single-photon sources using electro-optic frequency translation

Heralded single-photon sources are a standard experimental tool for studying quantum optics and quantum information in few-photon systems. These sources use spontaneous parametric wave mixing to probabilistically emit pairs of photons. One photon of the pair, the heralding photon, is detected to indicate the presence of the other. In theory, the maximal probability of emitting a single pair of photons is 1/4. In practice, the typical probability is restricted to a few percent to suppress multi-pair emission. This is a major obstacle to experiments utilizing multiple single photons, which require simultaneous output from numerous independent sources. A potential solution is to multiplex many heralded sources and route an emitted photon to the predetermined output mode [1, 2]. A number of multiplexing schemes have been investigated; however the operation of many identical heralded sources along with fast efficient routing remains a challenge. A recently reported frequency-multiplexing scheme is based on a single continuous-wave parametric down-conversion (PDC) process that generates photon pairs with highly correlated frequencies [3]. This way different frequency channels in one physical component act as independent sources. However the heralding and routing by nonlinear frequency conversion required a number of components (detectors and pump lasers, respectively) that increased in proportion to the number of effective heralded sources.