Cryogenic integrated spontaneous parametric down-conversion

TL;DR

This paper demonstrates that spontaneous parametric down-conversion in nonlinear waveguides remains effective at cryogenic temperatures, enabling integration with superconducting detectors for scalable quantum photonics.

Contribution

It shows that SPDC in nonlinear waveguides is compatible with cryogenic conditions, facilitating integrated quantum photonics with superconducting detectors.

Findings

Heralding efficiency is maintained at cryogenic temperatures.

Spectral properties of SPDC are preserved at 4 K.

Second-order correlation functions remain consistent across temperatures.

Abstract

Scalable quantum photonics relies on interfacing many optical components under mutually compatible operating conditions. To that end, we demonstrate that spontaneous parametric down-conversion (SPDC) in nonlinear waveguides, a standard technology for generating entangled photon pairs, squeezed states, and heralded single photons, is fully compatible with cryogenic operating conditions required for superconducting detectors. This is necessary for the proliferation of integrated quantum photonics in integration platforms exploiting quasi-phase-matched second-order nonlinear interactions. We investigate how cryogenic operation at 4 K affects the SPDC process by comparing the heralding efficiency, second-order correlation function and spectral properties with operation at room temperature.