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arXiv · 2303.17428

Degenerate Photons from a Cryogenic Spontaneous Parametric Down-Conversion Source

Nina Amelie Lange·Timon Schapeler·Jan Philipp Höpker·Maximilian Protte·Tim J. Bartley
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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 $\pm$ 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.

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Nina Amelie Lange, Timon Schapeler, Jan Philipp Höpker, Maximilian Protte, Tim J. Bartley. 2023-03-30. Degenerate Photons from a Cryogenic Spontaneous Parametric Down-Conversion Source. https://doi.org/10.1103/physreva.108.023701

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