Super-Heisenberg-limited Sensing via Collective Subradiance in Waveguide QED

TL;DR

This paper demonstrates how collective subradiance in waveguide QED systems can be exploited to achieve super-Heisenberg-limited sensing, with enhanced precision scaling as N^6, robust against disorder.

Contribution

It introduces a universal scaling law for subradiant decay rates and shows how these states enable quantum metrology surpassing traditional limits.

Findings

Decay rate scales as N^{-3} with even-odd oscillations

Quantum Fisher information scales as N^6

Robustness of subradiant states under disorder

Abstract

We explore the quantum-metrological potential of subwavelength-spaced emitter arrays coupled to a one-dimensional nanophotonic waveguide. In this system, strong dipole--dipole interactions profoundly modify the collective optical response, leading to the emergence of ultranarrow subradiant resonances. Through an eigenmode analysis of the effective non-Hermitian Hamiltonian, we derive a universal scaling law for the decay rate of the most subradiant state, which exhibits an $ N^{-3} $ scaling with even-odd oscillatory behavior in the deep-subwavelength regime. This scaling is directly observable in the single-photon scattering spectrum, enabling the detection of minute changes in atomic separation with a figure of merit that scales as $ N^3 $. The quantum Fisher information (QFI) scales as $N^6$ and can be closely approached by measuring spectral shifts near the steepest slope of the most subradiant resonance. These enhancements remain robust under realistic positional disorder, confirming that dipole--dipole-engineered subradiance provides a viable resource for quantum metrology. Our work bridges many-body waveguide quantum electrodynamics and high-precision sensing, opening a route toward scalable quantum sensors on integrated nanophotonic platforms.