Fast High-Fidelity Single-Shot Readout of Spins in Silicon Using a Single-Electron Box

Three key metrics for readout systems in quantum processors are measurement\nspeed, fidelity and footprint. Fast high-fidelity readout enables mid-circuit\nmeasurements, a necessary feature for many dynamic algorithms and quantum error\ncorrection, while a small footprint facilitates the design of scalable,\nhighly-connected architectures with the associated increase in computing\nperformance. Here, we present two complementary demonstrations of fast\nhigh-fidelity single-shot readout of spins in silicon quantum dots using a\ncompact, dispersive charge sensor: a radio-frequency single-electron box. The\nsensor, despite requiring fewer electrodes than conventional detectors,\nperforms at the state-of-the-art achieving spin read-out fidelity of 99.2% in\nless than 6 $\\mu$s. We demonstrate that low-loss high-impedance resonators,\nhighly coupled to the sensing dot, in conjunction with Josephson parametric\namplification are instrumental in achieving optimal performance. We quantify\nthe benefit of Pauli spin blockade over spin-dependent tunneling to a\nreservoir, as the spin-to-charge conversion mechanism in these readout schemes.\nOur results place dispersive charge sensing at the forefront of readout\nmethodologies for scalable semiconductor spin-based quantum processors.\n