Abstract
It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Actively multiplexing photons generated in many temporal modes can decouple these probabilities, but key issues are to minimize resource requirements to allow scalability, and to ensure indistinguishability of the generated photons. Here we demonstrate the multiplexing of photons from four temporal modes solely using fibre-integrated optics and off-the-shelf electronic components. We show a 100% enhancement to the single-photon output probability without introducing additional multi-photon noise. Photon indistinguishability is confirmed by a fourfold Hong–Ou–Mandel quantum interference with a 91±16% visibility after subtracting multi-photon noise due to high pump power. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies.
Highlights
It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes
The alternative approach is to generate correlated photon pairs via spontaneous nonlinear optical processes, such as parametric down conversion or four-wave mixing in suitable crystals or waveguides, where the detection of one photon in a pair ‘heralds’ the existence of its partner[15,16,17]
A promising solution is to actively multiplex non-deterministic photons in different spatial or temporal modes to enhance the probability of single-photon output[19,20,21,22,23]
Summary
It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Single particles of light—photons—are a vital resource for the implementation of quantum-enhanced technologies such as optical quantum computing[1] and simulation[2] To make such technologies practical requires ideal single-photon sources, which can emit single photons on-demand and indistinguishable in all relevant degrees of freedom: central frequency, bandwidth, spatial mode, and polarization[3,4]. Two groups have demonstrated initial experimental implementations of active temporal multiplexing[27,28], but the remaining challenges are: managing the photons’ arrival time to the accuracy of several picoseconds, and controlling their polarization to maintain the photons’ indistinguishability; and developing ultra-low-loss integrated optical components so that the desired enhancement can be achieved in a scalable manner. We show a substantial increase in the heralded single-photon output probability at a given clock cycle with no concomitant increase in the multi-pair contamination
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