$1/N^2$ Precision Interferometry with Collectively Enhanced Atomic Mirror

TL;DR

This paper presents a quantum metrology scheme using a collective atomic mirror that achieves $1/N^2$ precision scaling without entangled states, surpassing the Heisenberg limit.

Contribution

Introducing a collectively enhanced quantum mirror protocol that attains super-Heisenberg precision scaling without entanglement, leveraging cooperative optical response.

Findings

Achieves $1/N^2$ precision scaling in boundary distance estimation.

Surpasses the Heisenberg limit with a non-entangled, collective approach.

Robust against positional and coupling disorder.

Abstract

Quantum metrology exploits quantum resources to enhance measurement precision beyond the classical limit. Conventional protocols normally rely on the preparation of delicate quantum states to acquire these resources, posing a major challenge for scaling and robustness. Here we introduce a paradigm that circumvents this requirement with a collectively enhanced quantum mirror (CEAM), i.e., a mesoscopic array of $N$ atoms coupled to a semi-infinite waveguide. When injecting single photons into the waveguide and estimating the CEAM-boundary distance from the reflection phase, a $1/N^2$ precision scaling can be obtained, which surpasses the Heisenberg limit. In this protocol, the quantum resource stems from the cooperative optical response, requiring no entangled state preparation. Our scheme is robust against positional and coupling disorder, offering a practical route to ultra-sensitive quantum metrology in integrated photonic systems.