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Q: Fachverband Quantenoptik und Photonik

Q 57: Quantum Information (Quantum Repeater)

Q 57.3: Talk

Friday, March 13, 2020, 11:45–12:00, e001

Optimized cavity-enhanced down-conversion source in interferometric configuration — •Jan Arenskötter, Stephan Kucera, and Jürgen Eschner — Universität des Saarlandes, Experimentalphysik, Campus E2.6, 66123 Saarbrücken

An efficient resource of entanglement in atom-photon-based quantum networks are polarization-entangled photon pairs generated by type-II spontaneous parametric down-conversion (SPDC). Previously, we presented a cavity-enhanced SPDC source in interferometric configuration, which is tailored to match the P_3/2 to D_5/2 transition of ⁴⁰Ca⁺ at 854 nm [1].

Here we show improvements and optimizations of this photon pair source. We changed the cavity geometry from a bow-tie to a triangle configuration which resulted in a shortening of the cavity length. By this we improve the scaling of the signal-to-background ratio due to an increased bandwidth of the photons. The photons coming from the new source are non-degenerate but still show polarization entanglement with a fidelity of at least 97.9% to the Ψ⁻-Bell state. The locking scheme of the cavity and the interferometer have also been improved for better signals and higher stability.

[1] DPG Verhandlungen Q2.7, Mainz 2017