Noise Correlations in a 1D Silicon Spin Qubit Array

TL;DR

This study investigates how charge noise correlations between silicon quantum dot pairs vary with distance, revealing that correlations decrease significantly as inter-dot distance increases, and identifies surface charge fluctuations as the primary noise source.

Contribution

It provides the first detailed measurement of spatially dependent charge noise correlations in silicon spin qubits and links these correlations to surface two-level fluctuators.

Findings

Charge noise correlations decrease from >0.5 to <0.1 as distance increases from 75nm to 300nm.

Surface two-level fluctuators are identified as the main source of correlated noise.

Correlation magnitude is significantly suppressed at larger inter-dot distances.

Abstract

Correlated noise across multi-qubit architectures is known to be highly detrimental to the operation of error correcting codes and the long-term feasibility of quantum processors. The recent discovery of spatially dependent correlated noise in multi-qubit architectures of superconducting qubits arising from the impact of cosmic radiation and high-energy particles giving rise to quasiparticle poisoning within the substrate has led to intense investigations of mitigation strategies to address this. In contrast correlated noise in semiconductor spin qubits as a function of distance has not been reported to date. Here we report the magnitude, frequency and spatial dependence of noise correlations between four silicon quantum dot pairs as a function of inter-dot distance at frequencies from 0.3mHz to 1mHz. We find the magnitude of charge noise correlations, quantified by the magnitude square coherence $C_{xy}$, are significantly suppressed from $>0.5$ to $<0.1$ as the inter-dot distance increases from 75nm to 300nm. Using an analytical model we confirm that, in contrast to superconducting qubits, the dominant source of correlated noise arises from low frequency charge noise from the presence of two level fluctuators (TLFs) at the native silicon-silicon dioxide surface. Knowing this, we conclude with an important and timely discussion of charge noise mitigation strategies.