Special CPM Seminar

Atomistic modelling of exchange interaction in silicon qubits

Rajib Rahman

School of Physics
University of New South Wales

Spin qubits hosted in dopant atoms and in gate defined quantum dots in silicon are promising candidates for a scalable quantum computer [1]. These qubits benefit from exceptional coherence times, compatibility with the silicon transistor technology, and mature material and device processing capabilities at the industrial level. The exchange interaction between electrons has been the principal mechanism for two-qubit coupling in silicon. However, the indirect gap six-fold valley conduction band valley degeneracy of bulk silicon strongly affects the exchange coupling. Additionally, device geometry and gate voltages offer the ability to tune this coupling. We developed an atomistic full configuration interaction (AFCI) method to capture exchange and correlation between qubits. We apply this method to investigate how the exchange coupling can be engineered by device design in a three-qubit device in comparison with experiment [2]. We also investigate the role of valley interference in donor qubits in silicon and suggest ways to mitigate these detrimental effects [3]. Furthermore, we show how to engineer giant exchange couplings in donor atom qubits through electrical control [4]. The simulations help our experimental partners to design robust two-qubit gates in silicon.

References:
[1] F. A. Zwanenburg et. al., Rev. Mod. Phys. 85, 961 (2013).
[2] K. W. Chan et. al., NanoLetters 21, 1517 (2021).
[3] B. Voisin et. al., Nature Comm. 11, 1 (2020).
[4] Y. Wang et. al., NPJ Quant. Info. 2, 16008 (2016).