# Quantum metrology enhanced by coherence-induced-driving in a cavity QED setup

## TL;DR

This paper presents a quantum metrology scheme in cavity QED that achieves the Heisenberg limit without requiring atomic entanglement, by leveraging atomic coherence to induce an effective driving of the cavity field.

## Contribution

It introduces a novel approach to quantum metrology that uses atomic coherence to reach the Heisenberg limit without entanglement preparation.

## Key findings

- Achieves Heisenberg limit in measurement precision.
- Uses atomic coherence to induce cavity field dynamics.
- Demonstrates proportionality of fluctuations to 1/N_c^2.

## Abstract

We propose a quantum metrology scheme in a cavity QED setup to achieve the Heisenberg limit. In our scheme, a series of identical two-level atoms randomly pass through and interact with a dissipative single-mode cavity. Different from the entanglement based Heisenberg limit metrology scheme, we do not need to prepare the atomic entangled states before they enter into the cavity. We show that the initial atomic coherence will induce an effective driving to the cavity field, whose steady state is an incoherent superposition of orthogonal states, with the superposition probabilities being dependent on the atom-cavity coupling strength. By measuring the average photon number of the cavity in the steady state, we demonstrate that the root-mean-square of the fluctuation of the atom-cavity coupling strength is proportional to $1/N_c^2$ ($N_c$ is the effective atom number interacting with the photon in the cavity during its lifetime). It implies that we have achieved the Heisenberg limit in our quantum metrology process. We also discuss the experimental feasibility of our theoretical proposal. Our findings may find potential applications in quantum metrology technology.