Revealing inadvertent periodic modulation of qubit frequency

TL;DR

This paper presents a method to detect and characterize slow periodic frequency modulations in qubits, which can affect their stability, using spectral analysis of Ramsey measurement outcomes.

Contribution

It introduces a spectral analysis technique to reveal and quantify slow periodic frequency modulations in qubits, including effects of fluctuations.

Findings

Sharp peaks in power spectrum indicate modulation frequency and amplitude

Analytical results match extensive simulations

Method detects slow frequency fluctuations affecting qubit stability

Abstract

The paper describes the means to reveal and characterize slow periodic modulation of qubit frequency. Such modulation can come from different sources and can impact qubit stability. We show that the modulation leads to very sharp peaks in the power spectrum of outcomes of periodically repeated Ramsey measurements. The positions and shapes of the peaks allow finding both the frequency and the amplitude of the modulation. We also explore how additional slow fluctuations of the qubit frequency and fluctuations of the modulation frequency affect the spectrum. The analytical results are in excellent agreement with extensive simulations.