Noise Spectroscopy Using Correlations of Single-Shot Qubit Readout

TL;DR

This paper introduces a new method for noise spectroscopy in qubits using correlations of single-shot readouts, enabling spectrum extraction without requiring complex control sequences or long relaxation times.

Contribution

The authors present an alternative noise spectroscopy technique based on single-shot measurement correlations, which is simpler and more versatile than existing methods.

Findings

Effective measurement of $1/f$ noise spectrum.

Ability to tune sensitivity and frequency range independently.

Applicable to nuclear bath fluctuations in GaAs spin qubits.

Abstract

A better understanding of the noise causing qubit decoherence is crucial for improving qubit performance. The noise spectrum affecting the qubit may be extracted by measuring dephasing under the application of pulse sequences but requires accurate qubit control and sufficiently long relaxation times, which are not always available. Here, we describe an alternative method to extract the spectrum from correlations of single-shot measurement outcomes of successive free induction decays. This method only requires qubit initialization and readout with a moderate fidelity and also allows independent tuning of both the overall sensitivity and the frequency region over which it is sensitive. Thus, it is possible to maintain a good detection contrast over a very wide frequency range. We discuss using our method for measuring both $1/f$ noise and the fluctuation spectrum of the nuclear bath of GaAs spin qubits.