Erlangen 2022 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 54: Quantum Information (Quantum Repeater)

Q 54.3: Talk

Thursday, March 17, 2022, 14:30–14:45, Q-H12

A one-node quantum repeater — Stefan Langenfeld, Philip Thomas, •Olivier Morin, and Gerhard Rempe — Max-Planck-Institute für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching

For long distance quantum communication, losses in optical fibers constitute a real hurdle. Indeed, because the transmission efficiency scales exponentially with distance, any qubit exchange is basically impossible beyond typically 500km. The quantum repeater solves this problem via an improved rate-versus-distance scaling by dividing a long link into multiple short ones.

Using a cavity QED platform, ⁸⁷Rb atoms in a high-finesse optical cavity, we have developed all the necessary features required to implement a quantum repeater: long coherence time qubit memories [1], accurate control of the photon shape [2], low-cross-talk random access memories [3]. With these capabilities in hand, we have implemented an elementary quantum repeater. At the central node, two atoms send photons (entangled with the atomic states) repeatedly until it is received by each end of the link. Eventually, a Bell measurement is realized on the two atoms which entangles the two ends of the link. With this experimental realization, we observed an improvement by a factor 2 in the rate-versus-distance scaling, the central feature of a quantum repeater [4].

[1] M. Körber et al., Nat. Photonics 12, 18 (2018).

[2] O. Morin et al., Phys. Rev. Lett. 123, 133602 (2019).

[3] S. Langenfeld et al., npj Quantum Inf 6, 86 (2020).

[4] S. Langenfeld et al., Phys. Rev. Lett. 126, 230506 (2021).