Title: Fast Optical-control of a Coherent Hole-spin in a Microcavity
When: Tuesday, July 02, 2024, 12:00
Place: Department of Theoretical Condensed Matter Physics, Faculty of Sciences, Module 5, Seminar Room (5th Floor)
Speaker: Malwina Anna Marczak, University of Basel, Switzerland.
Spin-photon interfaces are a key ingredient for quantum technologies, enabling quantum information to be mapped between stationary spins and photons travelling at the speed of light. They can also be used as a deterministic source of entangled photonic graph-states, which are resource states for measurement-based quantum computation and one-way quantum repeaters. The ideal spin-photon interface combines both a highly coherent spin and coherent, efficient photon emission. Self-assembled semiconductor quantum dots (QDs) are demonstrated excellent on-demand sources of indistinguishable, single-photons. Gated devices allow deterministic charging of the QDs, and impressive progress has been achieved in mitigating the impact of magnetic noise from the host nuclear spins on electron-spin decoherence. Here, we demonstrate a system with which we achieve fast and high-fidelity coherent control of a QD hole-spin, a spin decoherence-time T2* of 500 ns, all on a QD embedded in a tunable open microcavity with an exceptionally high end-to-end single photon source efficiency. Many spin rotations can be carried out and many photons can be created before the spin loses its coherence; the photons are extracted with high efficiency. We use a microwave-modulated control scheme, making coherent rotations around an arbitrary Bloch sphere axis trivial and allowing all-optical cooling of the host nuclei to extend the hole spin coherence. We achieve a maximum π-pulse fidelity of 98.7%, and ultra-fast Rabi frequencies above 1 GHz. Our work demonstrates the potential for semiconductor QDs as fast, efficient, and coherent spin-photon interfaces.
