Abstract
Silicon quantum dots are considered an excellent platform for spin qubits, partly due to their weak spin-orbit interaction. However, the sharp interfaces in the heterostructures induce a small but 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 derivative of 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 interactions 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, which we conclude is dominated by momentum-term spin-orbit interactions that varies from 1.85 MHz up to 27.5 MHz depending on the magnetic field orientation. Finally, we exploit the tunability of the derivative of the Stark shift of one of the dots to reduce its sensitivity to electric noise and observe an 80 % increase in $T_2^*$. We conclude that the tuning of the spin-orbit interaction will be crucial for scalable quantum computing in silicon and that the optimal setting will depend on the exact mode of qubit operations used.
Highlights
Silicon-based spin qubits have attracted attention as candidates for large-scale quantum computing thanks to their long coherence times, excellent controllability, and fabrication techniques, which are well established in the semiconductor industry [1,2,3,4,5,6,7,8,9,10,11,12,13]
We show the measurements taken with the magnetic field in plane with the sample in Fig. 1(c), together with measurements taken at 45 degrees out of plane
In a silicon quantum-dot qubit array, the spin-orbit interaction (SOI) can vary from one dot to another, which leads to a variety of gfactors [14]
Summary
Silicon-based spin qubits have attracted attention as candidates for large-scale quantum computing thanks to their long coherence times, excellent controllability, and fabrication techniques, which are well established in the semiconductor industry [1,2,3,4,5,6,7,8,9,10,11,12,13]. SOI is responsible for effects such as the Stark shift of the electron spin resonance (ESR) frequency, variation of Lande g-factors, and mixing between singlet (S) and polarized triplet (T−) states [15,16,17,18]. The g-factor, Stark shift, and S-T− mixing exhibit sinusoidal dependence on the magnetic field direction, as reported before [12,15,17,26] We use these measurements to extract the Rashba and Dresselhaus interaction strengths of the lowerenergy-valley state in both of the dots. This minimization could be extremely useful in reducing errors during spin shuttling of electron spins in a quantum bus, or in reducing undesired leakage to the T− state in the S-T operational basis
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