Abstract
Evolving photonic quantum technologies and applications require higher and higher rates of single photon generation. In parallel, it is required that these generated photons are kept spectrally pure for multi-photon experiments and that multi-photon noise be kept to a minimum. In spontaneous parametric down-conversion sources, these requirements are conflicting, because spectral filtering to increase spectral purity always means lowering the rate at which photons are generated, and increasing the pump power means increasing the multi-photon noise. In this paper, we present a scheme, called extended heralding, which aims to mitigate the reduction of single-photon generation rate under spectral filtering by removing cases where we detect light in the rejection band of the heralding photon’s filter. Our experiment shows that this allows for higher single-photon generation rates with lower multi-photon noise than the standard approach of neglecting modes falling out of the filter bandwidth. We also show that by using active feed-forward control based on this extended heralding, it is possible to further improve the performance of the original source by physically eliminating uncorrelated photons from the output stream.
Highlights
Many important tasks in optical quantum information processing, like boson sampling [1, 2, 3], linear optics quantum computing [4, 5], and quantum networking [6, 7], require the generation of single-photon states at high rates and with high purity
Current methods for single-photon generation include parametric downconversion (PDC) processes in non-linear crystals and waveguides [8, 9], four-wave mixing in optical fibers and waveguides [10, 11, 12], and quantum dots [13, 14, 15] and color centers [16, 17, 18] in solid state lattices
The heralding rate goes with pf, the filtered photon production probability, while the noise in the heralding arm depends on p (> pf ), the original production probability before filtering
Summary
Many important tasks in optical quantum information processing, like boson sampling [1, 2, 3], linear optics quantum computing [4, 5], and quantum networking [6, 7], require the generation of single-photon states at high rates and with high purity. All of these technologies are able to produce single photons, the de facto standard in applications is still PDC sources based on non-linear crystals, due the proven technology behind their manufacturing processes and simple opreration They are compact, able to produce photon states of high spectral purity and indistinguishability [19, 20] and easy to package in integrated, room-temperature devices [21, 22]. Increasing the pump power to recover the “lost” heralding rate will introduce substantial multi-photon noise, such that increasing the pump power is not a viable solution This is because the filter is applied only to the heralding arm to maintain high heralding efficiency of the heralded photon [25], and light which is outside the filter in the heralding arm does not lead to heralding events. The heralding rate goes with pf , the filtered photon production probability, while the noise in the heralding arm depends on p (> pf ), the original production probability before filtering
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