A Quantum Dot Source of Time-Bin Multi-Photon Entanglement
September 27th, 2021 MARTIN HAYHURST APPEL Center for Hybrid Quantum Networks, The Niels Bohr Institute
University of Copenhagen

Quantum states of multiple entangled photons constitute an important resource for quantum information processing. In this talk, I’ll report on experimental work towards deterministic entanglement generation using a solid-state quantum dot embedded in a photonic crystal waveguide. A common limitation encountered with quantum dots is the incompatibility of coherent spin control and optical cycling transitions. By applying an in-plane magnetic field and by selectively coupling the linear optical dipoles to the waveguide mode, we measure a broadband increase in optical cyclicity up to 14.7 while retaining the ability to drive optical Raman transitions and perform high fidelity optical spin pumping. These capabilities allow the realisation of a time-bin entanglement protocol. By combining resonant optical pulses and Raman pulses, the protocol can generate GHZ states and linear cluster states containing the QD spin and N photons, where each photon is emitted in a superposition of two temporal modes. By using a novel self-stabilising double pass interferometer, we measure a spin-photon Bell state with a 66.6% fidelity and 124 Hz detection rate. This fidelity is well reproduced by a Monte Carlo simulation, and realistic improvements should allow us to achieve error rates of 2.1% pr. photon for realistic parameters.

Seminar, September 27, 2021, 16:00. Seminar Room

Hosted by Prof. Hugues de Riedmatten