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Thesis defence Zhiren Wang May 9th 2023

Thesis Zhiren Wang.png
Zhiren Wang.png

Single spins in solids are good candidates for implementing quantum bits for quantum information processing thanks to their long coherence times. However, being individual atomic-scale quantum objects, they are difficult to address and to entangle with one another. This thesis work explores two distinct but related approaches for manipulating and detecting single spins, both involving comparable hybrid circuit quantum electrodynamics platforms operated at millikelvin temperatures. In the first approach, single electron spin resonance (ESR) is demonstrated by spin fluorescence detection : a microwave photon counter is used to detect the photon emitted by an excited spin. The spins are paramagnetic erbium ions in a scheelite crystal, and are coupled magnetically to a high-quality factor planar superconducting resonator. They are detected individually with a signal-to-noise ratio of 1.9 in a one second-integration time. The fluorescence signal shows anti-bunching, proving that it comes from individual emitters. Coherence times up to 3 ms are measured, limited by the engineered spin radiative lifetime. This single-spin quantum control experiment also opens the route to new applications of ESR, in particular for microscopic object characterization. In the second approach, the detection of spins is based on leveraging the charge degree of freedom of hole spins and their strong intrinsic spin-orbit interaction. We demonstrate a compact novel platform made of electrostatically defined quantum dots in AlGaAs/GaAs heterostructure, filled with hole spins by optical illumination. The spins are coupled electrically to a superconducting resonator for probing their charge and spin states. Using this resonator as a dispersive readout, we show that single charge tunneling events in the dots can be detected after illumination. This represents a critical step towards addressing single hole spin in a semiconductor. Overall, the two methods reported in this thesis open new avenues for the development of quantum sensing and quantum computing applications.

Annual Meeting April 2023 in Grenoble, France

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