A high-sensitivity charge sensor for silicon qubits above one kelvin

TL;DR

This paper introduces a double-island SET (DISET) charge sensor that significantly outperforms traditional SISET sensors in sensitivity and fidelity at temperatures above 1 K, enabling high-fidelity qubit readout at higher temperatures.

Contribution

The authors demonstrate a DISET-based charge sensor with an order of magnitude better signal-to-noise ratio and over 99% single-shot readout fidelity up to 8 K, surpassing standard SISET performance.

Findings

DISET improves charge sensing sensitivity by an order of magnitude.

Single-shot charge readout fidelity exceeds 99% up to 8 K.

Sensor performance aligns with theoretical models of temperature-dependent transport.

Abstract

Recent studies of silicon spin qubits at temperatures above 1 K are encouraging demonstrations that the cooling requirements for solid-state quantum computing can be considerably relaxed. However, qubit readout mechanisms that rely on charge sensing with a single-island single-electron transistor (SISET) quickly lose sensitivity due to thermal broadening of the electron distribution in the reservoirs. Here we exploit the tunneling between two quantised states in a double-island SET (DISET) to demonstrate a charge sensor with an improvement in signal-to-noise by an order of magnitude compared to a standard SISET, and a single-shot charge readout fidelity above 99 % up to 8 K at a bandwidth > 100 kHz. These improvements are consistent with our theoretical modelling of the temperature-dependent current transport for both types of SETs. With minor additional hardware overheads, these sensors can be integrated into existing qubit architectures for high fidelity charge readout at few-kelvin temperatures.