Anisotropy with respect to the applied magnetic field of spin qubit decoherence times

TL;DR

This paper explores how the anisotropy of spin qubit decoherence times with respect to magnetic field direction can reveal details about environmental noise sources affecting quantum dot devices.

Contribution

It introduces a method to analyze anisotropy patterns in $T_1$ and $T_{}$ to identify noise sources in spin qubits, supported by theoretical calculations.

Findings

Anisotropy patterns differ for charge, Johnson, and hyperfine noise.

Maximum benefit requires well-characterized samples.

Calculated anisotropy for Si/SiGe quantum dots supports the method.

Abstract

Electron spin qubits are a promising platform for quantum computation. Environmental noise impedes coherent operations by limiting the qubit relaxation ($T_1$) and dephasing ($T_{\phi}$) times. There are multiple sources of such noise, which makes it important to devise experimental techniques that can detect the spatial locations of these sources and determine the type of source. In this paper, we propose that anisotropy in $T_1$ and $T_{\phi}$ with respect to the direction of the applied magnetic field can reveal much about these aspects of the noise. We investigate the anisotropy patterns of charge noise, evanescent-wave Johnson noise, and hyperfine noise in hypothetical devices. It is necessary to have a rather well-characterized sample to get the maximum benefit from this technique. The general anisotropy patterns are elucidated. We calculate the expected anisotropy for a particular model of a Si/SiGe quantum dot device.