Coherent singlet-triplet dynamics in CMOS

Electric dipole spin resonance (EDSR) may be preferable over electron spin resonance, which requires large-footprint on-chip microwave lines carrying large currents that can cause heating. Then, the spin-driving electric fields can be generated locally with gate voltages, where industry-standard complementary metal-oxide-semiconductor (CMOS) processes can be applied to manufacture dense gate structures [1]. In silicon, intrinsic spin-orbit coupling (SOI) based EDSR has been demonstrated for hole spins [2,3]. For electron spin EDSR, SOI is typically introduced artificially with micromagnets [4], or by utilizing the valley-orbit interaction  instead [5]. Here, we study magnetic field and power dependence of inter-dot charge transitions in a $n$-doped CMOS nanowire few-quantum-dot device with gate-based radiofrequency (RF) reflectometry. We observe coherent double-passage Landau-Zener-Stuckelberg oscillations in a $S$-$T^{-}$ system, when driven at RF powers above the linear response regime. We vary the Stuckelberg phase with external magnetic field and detuning. Based on RF drive frequency of approximately $610$ MHZ, we estimate $T_{2}^{*} > 1.7 $ns. We numerically evaluate the parametric capacitance [6], to model the effective state space, and to estimate the relevant energy parameters, such as the SOI strength.  

[1] F. Ansaloni et al. “Single-electron operations in a foundry-fabricated arrayof quantum dots”. Natcomms (2020)

[2] L. C. Camenzind et al. “A spin qubit in a fin field-effect transistor”. arXiv (2021)

[3] A. Corna et al. “Electrically driven electron spin resonance mediated byspin–valley–orbit coupling in a silicon quantum dot”. NPJ QI (2018)

[4] A. Crippa et al. “Gate-reflectometry dispersive readout and coherent con-trol of a spin qubit in silicon”. Natcomms (2019)

[5] R. Mizuta et al. “Quantum and tunneling capacitance in charge and spinqubits”. PRB (2017)

[6] X. Wu et al. “Two-axis control of a singlet–triplet qubit with an integratedmicromagnet”. PNAS (2014)