Limits on the deterministic creation of pure single-photon states using parametric down-conversion

TL;DR

This paper analyzes the fundamental limits of using parametric down-conversion for generating high-quality, pure single-photon states, considering higher-order photon components and multiple modes, and discusses the feasibility of near-deterministic single-photon sources.

Contribution

It quantifies the maximum achievable fidelity and probability of single-photon generation using PDC with ideal conditions and proposes the number of sources needed for near-deterministic emission.

Findings

Maximum single-photon fidelity is 100% with perfect conditions.

Maximum probability of single-photon creation per attempt is 25%.

Approximately 17 sources are needed for >99% emission probability.

Abstract

Parametric down-conversion (PDC) is one of the most widely used methods to create pure single-photon states for quantum information applications. However little attention has been paid to higher-order photon components in the PDC process, yet these ultimately limit the prospects of generating single-photons of high quality. In this paper we investigate the impacts of higher-order photon components and multiple frequency modes on the heralding rates and single-photon fidelities. This enables us to determine the limits of PDC sources for single-photon generation. Our results show that a perfectly single-mode PDC source in conjunction with a photon-number resolving detector is ultimately capable of creating single-photon Fock states with unit fidelity and a maximal state creation probability of 25%. Hence an array of 17 switched sources is required to build a deterministic (>99% emission probability) pure single-photon source.