Berlin 2014 – scientific programme

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SYQR: Symposium Quantum Repeater

SYQR 4: Photon Sources for Quantum Networks

SYQR 4.5: Talk

Tuesday, March 18, 2014, 15:00–15:15, Kinosaal

Frequency Conversion of Single Photons from a SPDC Source — •Andreas Lenhard, Stephan Kucera, José Brito, Jürgen Eschner, and Christoph Becher — Universität des Saarlandes, FR 7.2 Experimentalphysik, Campus E2.6, 66123 Saarbrücken

Many quantum repeater schemes rely on the transfer of single photons or entangled states. Thus, long-range transmission in fibers requires photons at low-loss telecommunication wavelengths. We have recently demonstrated the frequency conversion of photons generated by a single quantum emitter in the near-infrared spectral region to the telecom bands via frequency down-conversion in a nonlinear medium [1]. The frequency conversion of an entangled photon is another basic building block to establish quantum networks.

Here we report on the frequency down-conversion of single photons from a photon pair source, resonant with an atomic transition of a quantum repeater node. The pairs are generated by a type-II spontaneous parametric downconversion process in a bulk KTP crystal. One photon of the pair is spectrally filtered to fit a transition of ⁴⁰Ca⁺-ions at 854 nm and used as a herald [2]. By mixing with a pump field at 2.5 µm in a nonlinear waveguide the partner photon is converted to the telecom O-band at 1313 nm with an over-all efficiency around 10 %. We show that the temporal correlation between the photon pairs is preserved in the conversion process by measuring the photon correlation functions.
1. S. Zaske et al., Phys. Rev. Lett. 109 (2012), 147404
2. N. Piro et al., Nat. Phys. 7 (2011), 17-20