Interface induced spin-orbit interaction in silicon quantum dots and prospects of scalability

Dr Kok Wai Chan
4pm Thursday 11 May 2017
CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus

Silicon (Si) quantum dots (QD) have been among the most prominent candidates for implementing spin based qubits with a potential for scalability, due to their exceptional coherence times and industry standard fabrication process. To build a large-scale quantum computer with Si QDs, we must address any dot-to-dot variations that can cause randomness in qubit operations.

In this work, we identify the presence of monoatomic steps at the Si/SiO2 interface as a dominant source of variations in the electron g-factors, which will cause qubit-to-qubit variability in the single qubit spin resonance frequencies. We compare our theoretical predictions with experiments on QDs at a Si/SiO2 interface, in which we observe significant differences in Stark shifts between QDs in two different samples, with varying dephasing times. More importantly, from our calculations we show that by employing the anisotropic nature of the spin-orbit interaction in a Si QD, we can minimise and control these variations. Ultimately, we predict an increase in the dephasing time of the Si QD spin qubits by at least an order of magnitude, by aligning the external DC magnetic field towards specific crystal orientations.

Access the related paper via arXiv:1703.03840