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HL: Fachverband Halbleiterphysik

HL 36: Focus Session: Integrated Quantum Photonics II

HL 36.1: Hauptvortrag

Dienstag, 17. März 2020, 14:00–14:30, POT 51

Towards One-way Quantum Repeaters with Spin Qubits in Nanophotonic Interfaces — •Tim Schröder — Institut für Physik, Humboldt-Universität zu Berlin — Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik

We show progress on theoretical concepts and experimental implementation of *One-Way* Quantum Repeaters. While to date *one-way* quantum repeater proposals rely on a relatively large number of resources, we introduce a scheme that requires only one single photon emitter and two ancilla qubits per communication node. We analyse achievable quantum communication rates and propose a physical implementation that is accessible with today*s technology [arXiv:1907.05101]. On the experimental side, we demonstrate coherent control of single InAs quantum dot electron spins in nanobeam waveguides and show that coherence times reach those of spins in bulk. We furthermore demonstrate nanobeam to fibre coupling efficiencies of 92%; together with waveguide*photon coupling of up to 0.95 this enables highly efficient photonic systems for the generation of multi-photon cluster states. Towards improving waveguide*photon coupling efficiencies beyond 0.95 we introduce a novel waveguide-integrated nanocavity and demonstrate a 30-fold quantum dot lifetime reduction. Finally, we demonstrate that quantum dot spin-photon interfaces in nanobeams are well suited for the demonstration of two-qubit gates, an important requirement for the generation of photonic cluster states. Towards this goal we show that a single waveguide-coupled quantum dot enables spin-state dependent transmission of single photon states.