A silicon singlet-triplet qubit driven by spin-valley coupling

TL;DR

This paper introduces a silicon-based singlet-triplet qubit driven by spin-valley coupling, enabling fast, high-fidelity control and detailed noise characterization in silicon quantum dots.

Contribution

It demonstrates a novel qubit operation mode driven by spin-valley coupling, achieving over 200 MHz control frequency and enabling detailed charge noise spectrum analysis.

Findings

Qubit operates at >200 MHz frequency.

Charge noise spectral density follows a 1/f^α dependence with α ~ 0.7.

Long-term frequency drift reveals low-frequency noise characteristics.

Abstract

Spin-orbit effects, inherent to electrons confined in quantum dots at a silicon heterointerface, provide a means to control electron spin qubits without the added complexity of on-chip, nanofabricated micromagnets or nearby coplanar striplines. Here, we demonstrate a novel singlet-triplet qubit operating mode that can drive qubit evolution at frequencies in excess of 200 MHz. This approach offers a means to electrically turn on and off fast control, while providing high logic gate orthogonality and long qubit dephasing times. We utilize this operational mode for dynamical decoupling experiments to probe the charge noise power spectrum in a silicon metal-oxide-semiconductor double quantum dot. In addition, we assess qubit frequency drift over longer timescales to capture low-frequency noise. We present the charge noise power spectral density up to 3 MHz, which exhibits a $1/f^{\alpha}$ dependence consistent with $\alpha \sim 0.7$, over 9 orders of magnitude in noise frequency.