Erlangen 2018 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 47: Quantum Information (Quantum Repeater)
Q 47.1: Gruppenbericht
Mittwoch, 7. März 2018, 14:00–14:30, K 1.020
High-fidelity entanglement between a trapped ion and a telecom photon via quantum frequency conversion — •Matthias Bock, Pascal Eich, Stephan Kucera, Matthias Kreis, Andreas Lenhard, Christoph Becher, and Jürgen Eschner — Universität des Saarlandes, FR Physik, Campus E2.6, 66123 Saarbrücken
Entanglement between a stationary quantum system and a photonic flying qubit is an essential ingredient of a quantum-repeater network. Most stationary quantum bits, however, have transition wavelengths in the blue, red or near-infrared spectral regions, whereas long-range fiber-communication requires wavelengths in the low-loss, low-dispersion telecom regime. A proven tool to interconnect flying qubits at visible/NIR wavelengths to the telecom bands is quantum frequency conversion.
Here we present a complete device that produces entangled states between an atomic Zeeman qubit in a single trapped 40Ca+ ion and the polarization state of a telecom photon with a Bell-state fidelity of 98.2 ± 0.2%. We achieve this by combining a trapped-ion quantum node producing ion-photon entanglement with a fidelity of 98.3 ± 0.3% and a polarization-preserving frequency converter connecting 854 nm to the telecom O-band. The converter, realized by difference-frequency generation in a PPLN waveguide embedded in single-crystal Mach-Zehnder-interferometer, combines 99.75 ± 0.18% process fidelity for the polarization-state conversion, 26.5% external conversion efficiency and 11.4 photons/s conversion-induced unconditional background.