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

We report the measurement of the electron spin orientation in a singly-occupied gate-defined quantum dot, fabricated using CMOS compatible processes at the 300 mm wafer-scale [1]. For readout, we employ spin-dependent tunnelling [2] combined with a low-footprint single-lead quantum dot charge sensor, measured using radiofrequency gate reflectometry [3]. We demonstrate spin readout, obtaining valley splittings in the range 0.5-0.7 meV and a maximum electron spin relaxation time (T₁) of 9 ± 3 s at 1 Tesla. These long lifetimes indicate that the silicon nanowire geometry and fabrication processes possess considerable promise for qubit devices, while this spin-readout method is well-suited to scalable architectures. We will discuss progress towards integrating such spin-readout with quantum-limited amplifiers [4].

[1] Nat. Commun. 7, 13575 (2016)
[2] Nature 430, 431 (2004)
[3] Nat. Commun. 6, 6084 (2015)
[4] Phys. Rev. Lett. 124, 67701 (2020)