Quantum Sensing of Weak Radio-Frequency Signals by Pulsed Mollow Absorption Spectroscopy

TL;DR

This paper introduces a novel quantum sensing method using Mollow triplet splitting in a nitrogen-vacancy center, enabling detection of GHz microwave fields beyond current sensitivity limits, with potential applications in quantum information and sensing.

Contribution

It demonstrates a new pulsed dynamical decoupling protocol based on Mollow triplet splitting for enhanced quantum sensing of high-frequency signals.

Findings

Detected GHz microwave fields below current detection limits.

Achieved sensitivity approaching the spectral linewidth limit.

Potential for applications in quantum coupling to phonons and photons.

Abstract

Quantum sensors, qubits sensitive to external fields, have become powerful detectors for various small acoustic and electromagnetic fields. A major key to their success have been dynamical decoupling protocols which enhance sensitivity to weak oscillating (AC) signals. Currently, those methods are limited to signal frequencies below a few MHz. Here we harness a quantum-optical effect, the Mollow triplet splitting of a strongly driven two-level system, to overcome this limitation. We microscopically understand this effect as a pulsed dynamical decoupling protocol and find that it enables sensitive detection of fields close to the driven transition. Employing a nitrogen-vacancy center, we detect GHz microwave fields with a signal strength (Rabi frequency) below the current detection limit, which is set by the center's spectral linewidth 1/T2*. Pushing detection sensitivity to the much lower 1/T2 limit, this scheme could enable various applications, most prominently coherent coupling to single phonons and microwave photons.