Freiburg 2024 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 44: Quantum Information II
Q 44.3: Talk
Thursday, March 14, 2024, 11:30–11:45, HS 1199
Enhancing the purity of single photons in parametric down- conversion through simultaneous pump-beam and crystal- domain engineering — •Baghdasar Baghdasaryan1,2, Fabian Steinlechner1,2,4, and Stephan Fritzsche1,3,5 — 1FSU Jena — 2IAP Jena — 3HI Jena — 4Fraunhofer IOF, Jena — 5TPI, 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 source; SPDC; entanglement; crystal engineering; pump engineering