Spectrally pure heralded single photons by spontaneous four-wave mixing in a fiber: reducing impact of dispersion fluctuations.

Jacob G Koefoed,Søren M M Friis,Jesper B Christensen,Karsten Rottwitt

doi:10.1364/oe.25.020835

Abstract

We model the spectral quantum-mechanical purity of heralded single photons from a photon-pair source based on nondegenerate spontaneous four-wave mixing taking the impact of distributed dispersion fluctuations into account. The considered photon-pair-generation scheme utilizes pump-pulse walk-off to produce pure heralded photons and phase matching is achieved through the dispersion properties of distinct spatial modes in a few-mode silica step-index fiber. We show that fiber-core-radius fluctuations in general severely impact the single-photon purity. Furthermore, by optimizing the fiber design we show that generation of single photons with very high spectral purity is feasible even in the presence of large core-radius fluctuations. At the same time, contamination from spontaneous Raman scattering is greatly mitigated by separating the single-photon frequency by more than 32 THz from the pump frequency.

Highlights

Many applications of quantum photonics, such as quantum cryptography [1, 2] and quantum computation [3, 4], rely critically on the ability to design single-photon sources with high generation rate, low noise and photon indistinguishability
An important subset of single-photon sources are pair sources based on the nonlinear optical effects of spontaneous parametric downconversion (SPDC) [5,6,7] or spontaneous four-wave mixing (SpFWM), the latter of which has been demonstrated in dispersion-shifted fibers [8], photonic crystal fibers (PCFs) [9,10,11] and silicon waveguides [12, 13]
We present a fiber design that effectively suppresses the impact of core-radius fluctuations (CRF) and document its performance by calculating the heralded purity and Hong-Ou-Mandel visibility, which we show to be significantly improved from the fiber discussed above

Summary

Introduction

Many applications of quantum photonics, such as quantum cryptography [1, 2] and quantum computation [3, 4], rely critically on the ability to design single-photon sources with high generation rate, low noise and photon indistinguishability. An important subset of single-photon sources are pair sources based on the nonlinear optical effects of spontaneous parametric downconversion (SPDC) [5,6,7] or spontaneous four-wave mixing (SpFWM), the latter of which has been demonstrated in dispersion-shifted fibers [8], photonic crystal fibers (PCFs) [9,10,11] and silicon waveguides [12, 13] Such sources are indeterministic in nature, one of the photons in the pair can be used to herald the presence of the other [14,15]. Little effort has been devoted to making photon-pair sources less vulnerable to dispersion fluctuations and understanding the limit that it imposes on e.g. fiber length and pump pulse durations

Objectives

Findings

Discussion

Conclusion