Improving SPDC single-photon sources via extended heralding and feed-forward control

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.

Directional emission of down-converted photons from a dielectric nano-resonator

“…To get an expression for the two-photon amplitude in terms of VSH (7) we substitute dyadic Green functions from previous section (A11) and E p pump field inside the nanoparticle (2) to the expression (5), where we apply the new notation for the VSH. Dyadic Green function for the idler photon coordinate as observer Ĝ(r i , r 0 , ω…”

“…Spontaneous parametric down-conversion (SPDC) is arguably the most widely used process for the generation of non-classical light [1]. On one hand, compared to quantum dots [2,3] and atomic defects [4], SPDC does not need cryogenic cooling to produce pure and indistinguishable heralded single photons [5] and correlated pairs of photons [6,7] at a high rate. It is a major advantage, since optical helium cryostats are incredibly bulky and expensive, thus preventing the proliferation of nonclassical light sources that require them.…”

Nonlinear Dielectric Nanoresonators and Metasurfaces: Toward Efficient Generation of Entangled Photons

“…This enables far reaching and versatile possibilities to control the properties of photon pairs by a suitably designed nonlinear optical system that controls the fields of the pump, signal, and idler waves. Such control allows the production of pure and indistinguishable heralded single photons [8] and correlated pairs of photons, [9,10] which have numerous applications in quantum optics. Among the nonlinear optical structures used for controlling the properties of generated photon pairs are suitably cut bulk crystals, waveguides, and optical fibers, as well as resonators.…”

Spatially multiplexed single-photon sources based on incomplete binary-tree multiplexers

“…The development of single-photon sources (SPSs) is of utmost importance for the effective realization of a number of experiments in the fields of photonic quantum technology and quantum information processing [1,2]. A promising realization of periodic SPSs are the heralded single-photon sources that can yield highly indistinguishable single photons in near-perfect spatial modes with known polarization [3][4][5][6][7]. In such sources, the detection of one member of a correlated photon pair generated in spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing (SFWM) heralds the presence of its twin photon.…”