Spin Readout of a CMOS Quantum Dot by Gate Reflectometry and Spin-Dependent Tunneling

Abstract

Silicon spin qubits are promising candidates for realizing large-scale quantum processors, benefitting from a magnetically quiet host material and the prospects of leveraging the mature silicon device fabrication industry. We report the measurement of an electron spin in a singly occupied gate-defined quantum dot, fabricated using CMOS-compatible processes at the 300-mm wafer scale. For readout, we employ spin-dependent tunneling combined with a low-footprint single-lead quantum-dot charge sensor, measured using rf gate reflectometry. We demonstrate spin readout in two devices using this technique, obtaining valley splittings in the range 0.5-0.7 meV using excited-state spectroscopy, and measure a maximum electron-spin relaxation time (T1) of 9±3 s at 1 T. These long lifetimes indicate the silicon-nanowire geometry and fabrication processes employed here show a great deal of promise for qubit devices, while the spin-readout method demonstrated here is well suited to a variety of scalable architectures.