Degenerate Photons from a Cryogenic Spontaneous Parametric Down-Conversion Source
arXiv:2303.17428 · doi:10.1103/PhysRevA.108.023701
Abstract
We demonstrate the generation of degenerate photon pairs from spontaneous parametric down-conversion in titanium in-diffused waveguides in lithium niobate at cryogenic temperatures. Since the phase-matching cannot be temperature tuned inside a cryostat, we rely on a precise empirical model of the refractive indices when fabricating a fixed poling period. We design the phase-matching properties of our periodic poling to enable signal and idler photons at (1559.3 0.6) nm, and characterize the indistinguishability of our photons by performing a Hong-Ou-Mandel interference measurement. Despite the effects of photorefraction and pyroelectricity, which can locally alter the phase-matching, we achieve cryogenic indistinguishable photons within 1.5 nm to our design wavelength. Our results verify 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.
arXiv comment7 pages, 6 figures
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