Charge sensing in CMOS devices using reflectometry

Spin qubits in silicon are great candidates for scalable quantum information processors due to their long coherence time and compatibility with industrial CMOS fabrication lines.[1] Usual spin-readout techniques imply spin-to-charge conversion and charge readout by transport measurement. This requires multiple leads and limits the scalability of the system. A solution is to do charge sensing using RF-reflectometry measurement[2] for which only one lead is necessary to control and read the qubit.[3] The critical part is to obtain an impedance matching, at low temperature, between the resonant circuit and the RF-line. Finding this matching condition can be challenging considering the temperature dependence of each of the tank circuit component and the sample-to-sample capacitance variability. A solution is to use a varactor[4] to adjust in situ the circuit impedance. In this talk, we report on optimization of reflectometry setups at low temperature and discuss the use of tunable capacitors for in situ tuning targeting high sensitivity RF-measurement for spin qubit readout.

[1] J. Yoneda, et al., Nat. Nano. 13, 102-106(2018)
[2] B. J. Villis, et al., Appl. Phys. Lett. 104, 233503(2014)
[3] P. Pakkiam, et al., Phys. Rev., 8, 041032(2018)
[4] N. Ares, et al., Phys. Rev., 5, 034011(2016)