Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 23: Poster I

Q 23.22: Poster

Tuesday, March 12, 2024, 17:00–19:00, Tent B

Enhancing the purity of single photons in parametric down-conversion through simultaneous pump-beam and crystal-domain engineering — •Baghdasar Baghdasaryan¹, Fabian Steinlechner^1,4,5, and Stephan Fritzsche^1,2,3 — ¹FSU Jena — ²HI Jena — ³TPI Jena — ⁴Fraunhofer IOF, Jena — ⁵IAP Jena

Spontaneous parametric down-conversion (SPDC) has shown great promise in the generation of pure and indistinguishable single photons. Photon pairs produced in bulk crystals are highly correlated in terms of transverse space and frequency. These correlations limit the indistinguishability of photons and result in inefficient photon sources. Domain-engineered crystals with a Gaussian nonlinear response have been explored to minimize spectral correlations. Here we study the impact of such domain engineering on spatial correlations of generated photons. We show that crystals with a Gaussian nonlinear response reduce the spatial correlations between photons. However, the Gaussian nonlinear response is not sufficient to fully eliminate the spatial correlations. Therefore, the development of a comprehensive method to minimize these correlations remains an open challenge. Our solution to this problem involves simultaneous engineering of the pump beam and crystal. We achieve purity of single-photon state up to 99% without any spatial filtering. Our findings provide valuable insights into the spatial waveform generated in structured SPDC crystals, with implications for applications such as boson sampling.

Keywords: single photon; pure photon; domain engineering; pump engineering