Influence of dynamical decoupling sequences with finite-width pulses on quantum sensing for AC magnetometry

TL;DR

This paper investigates how finite-width pulses in dynamical decoupling sequences affect AC magnetometry with nitrogen-vacancy centers, revealing deviations in optimal sensing times and proposing corrections for accurate quantum sensing.

Contribution

It provides both experimental and theoretical insights into the impact of finite pulse widths on quantum sensing accuracy and offers a correction method for improved AC field detection.

Findings

Finite pulse widths cause deviations in optimal phase accumulation time.

Correcting time-frequency conversion improves sensing accuracy.

Guidelines established for accurate AC field detection with finite-width pulses.

Abstract

Dynamical decoupling sequences with multiple pulses can be considered to exhibit filter functions for the time evolution of a qubit superposition state. They contribute to the improvement of coherence time and qubit-phase accumulation due to a time-varying field and can thus achieve high-frequency-resolution spectroscopy. Such behaviors find useful application in highly sensitive detection based on qubits for various external fields such as a magnetic field. Hence, decoupling sequences are indispensable tools for quantum sensing. In this study, we experimentally and theoretically investigated the effects of finite-width pulses in the sequences on AC magnetometry utilizing nitrogen-vacancy centers in an isotopically-controlled diamond. We revealed that the finite pulse widths cause a deviation of the optimum time to acquire the largest phase accumulation due to the sensing field from that expected by filter functions neglecting the pulse widths, even if the widths are considerably shorter than the time period of the sensing field. Moreover, we experimentally demonstrated that the deviation can be corrected by an appropriate time-frequency conversion. Our results provide a guideline for the detection of an AC field with an accurate frequency and linewidth in quantum sensing with multiple-pulse sequences.