In our paper, we demonstrate the generation of degenerate photon pairs from spontaneous parametric down-conversion (SPDC) in titanium-indiffused waveguides in lithium niobate at cryogenic temperatures. We characterize the indistinguishability of our photons with a Hong-Ou-Mandel interference measurement. We show sufficient understanding and control of the cryogenic nonlinear process, which has wider implications when combining quasi-phase-matched nonlinear optical processes with other cryogenic photonic quantum technologies, such as superconducting detectors.
The paper is available at:
https://doi.org/10.1103/PhysRevA.108.023701
