# 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.

## Key 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.

---
Source: https://tomesphere.com/paper/1702.06710