Controlling spin-orbit interactions in silicon quantum dots using magnetic field direction

Tuomo Tanttu, Bas Hensen, Kok Wai Chan, Henry Yang, Wister Huang, Michael Fogarty, Fay Hudson, Kohei Itoh, Dimitrie Culcer, Arne Laucht, Andrea Morello, Andrew Dzurak

Published 2018-07-27Version 1

Silicon quantum dots are considered as an excellent platform for spin qubits, partly due to their weak spin-orbit interaction. However, the sharp interfaces in the heterostructures induce a significant spin-orbit interaction which degrade the performance of the qubits or, when understood and controlled, could be used as a powerful resource. To understand how to control this interaction we build a detailed profile of the spin-orbit interaction of a silicon metal---oxide---semiconductor double quantum dot system. We probe the Stark shift, $g$-factor and $g$-factor difference for two single electron quantum dot qubits as a function of external magnetic field and find that they are dominated by spin-orbit interaction originating from the vector potential, consistent with recent theoretical predictions. Conversely, by populating the double dot with two electrons we probe the mixing of singlet and spin polarized triplet states during electron tunneling, dominated by momentum term spin orbit interactions. Finally, we exploit the tunability of the Stark shift of one of the dots to reduce its sensitivity to electric noise and observe an expected increase in $T_2^*$.