The role of Coulomb interactions in few-electron quantum dots in silicon

Gate-defined quantum dots in silicon are attractive systems for quantum computing thanks to the favorable material properties of silicon and their potential for scalability. Although single spins can be viewed as canonical qubits, in many situations researchers turn to multielectron dots to achieve better control, measurement or coherence properties. In this talk, I will describe our theoretical work investigating how Coulomb interactions affect the properties of qubits in Si/SiGe quantum dots. In the first part of the talk, I will discuss the interplay between these interactions and the valley physics in a two-electron quantum dot, with a particular focus on the singlet-triplet (ST) splitting due to its importance in qubit measurement and control [1,2]. I will also show how these results allow us to explain recent experiments that demonstrate wide-range tunability of the ST splitting and coherent manipulation of Wigner molecular states [3,4]. In the second part of the talk, I will focus on multielectron electrically driven spin resonance (EDSR) control. Other recent experiments in Si MOS have demonstrated that increasing the electron number in EDSR can lead to faster Rabi oscillations [5]. By providing comparisons between single- and three-electron systems I will describe the confinement and interface conditions that benefit dots with larger numbers of electrons and discuss prospects for further improvements [6].

 

[1] H. E. Ercan, et al., Phys. Rev. B 104, 235302 (2021).

[2] H. E. Ercan, et al., Phys. Rev. Lett. 128, 247701 (2022).

[3] J. P. Dodson, et al., Phys. Rev. Lett. 128, 146802 (2022).

[4] J. Corrigan, et al., Phys. Rev. Lett. 127, 127701 (2021).

[5] R. C. C. Leon, et al., Nature Communications 11, 797 (2020).

[6] H. E. Ercan, et al., manuscript in preparation.