Improved Single-Shot Qubit Readout Using Twin RF-SET Charge Correlations

TL;DR

This paper introduces a twin RF-SET correlation technique that significantly improves qubit readout fidelity in silicon quantum dot arrays, enabling faster and more accurate measurements crucial for quantum error correction.

Contribution

The paper presents a novel correlation-based readout method using twin RF-SETs that enhances fidelity and speed, especially for distant charge sensors in large qubit arrays.

Findings

Over one order of magnitude reduction in readout infidelity.

Faster modulation frequencies avoid relaxation errors.

Enhanced detection of charge transitions farther from sensors.

Abstract

High fidelity qubit readout is critical in order to obtain the thresholds needed to implement quantum error correction protocols and achieve fault-tolerant quantum computing. Large-scale silicon qubit devices will have densely-packed arrays of quantum dots with multiple charge sensors that are, on average, farther away from the quantum dots, entailing a reduction in readout fidelities. Here, we present a readout technique that enhances the readout fidelity in a linear SiMOS 4-dot array by amplifying correlations between a pair of single-electron transistors, known as a twin SET. By recording and subsequently correlating the twin SET traces as we modulate the dot detuning across a charge transition, we demonstrate a reduction in the charge readout infidelity by over one order of magnitude compared to traditional readout methods. We also study the spin-to-charge conversion errors introduced by the modulation technique, and conclude that faster modulation frequencies avoid relaxation-induced errors without introducing significant spin flip errors, favouring the use of the technique at short integration times. This method not only allows for faster and higher fidelity qubit measurements, but it also enhances the signal corresponding to charge transitions that take place farther away from the sensors, enabling a way to circumvent the reduction in readout fidelities in large arrays of qubits.