# Squeezing metrology: a unified framework

## TL;DR

This paper develops a unified theoretical framework for quantum metrology using squeezing, demonstrating that squeezing can achieve quadratic resolution gains similar to entanglement-based methods across various quantum systems.

## Contribution

It introduces a general theory quantifying the Heisenberg squeezing bound for arbitrary estimation strategies employing squeezing, unifying existing results across different quantum systems.

## Key findings

- Quadratic resolution gain achievable with squeezing comparable to entanglement-based methods.
- The framework applies broadly to quantum optics, spin squeezing, and other quantum systems.
- Recovery of known results within a unified theoretical approach.

## Abstract

Quantum metrology theory has up to now focused on the resolution gains obtainable thanks to the entanglement among N probes. Typically, a quadratic gain in resolution is achievable, going from the 1/sqrt(N) of the central limit theorem to the 1/N of the Heisenberg bound. Here we focus instead on quantum squeezing and provide a unified framework for metrology with squeezing, showing that, similarly, one can generally attain a quadratic gain when comparing the resolution achievable by a squeezed probe to the best N-probe classical strategy achievable with the same energy. Namely, here we give a quantification of the Heisenberg squeezing bound for arbitrary estimation strategies that employ squeezing. Our theory recovers known results (e.g.~in quantum optics and spin squeezing), but it uses the general theory of squeezing and holds for arbitrary quantum systems.