Gain-induced group delay in spontaneous parametric down-conversion

TL;DR

This paper reports the experimental observation of a gain-induced group delay in high-gain spontaneous parametric down-conversion, highlighting its impact on photon indistinguishability in quantum interference applications.

Contribution

It introduces and demonstrates the physical effect of gain-induced group delay in high-gain nonlinear optical processes, which was not characterized before.

Findings

Experimental observation of gain-induced group delay

Delay affects photon indistinguishability in quantum devices

Implications for designing quantum interference systems

Abstract

Strongly-driven nonlinear optical processes such as spontaneous parametric down-conversion and spontaneous four-wave mixing can produce multiphoton nonclassical beams of light which have applications in quantum information processing and sensing. In contrast to the low-gain regime, new physical effects arise in a high-gain regime due to the interactions between the nonclassical light and the strong pump driving the nonlinear process. Here, we describe and experimentally observe a gain-induced group delay between the multiphoton pulses generated in a high-gain type-II spontaneous parametric down-conversion source. Since the group delay introduces distinguishability between the generated photons, it will be important to compensate for it when designing quantum interference devices in which strong optical nonlinearities are required.