Arrays of emitters with subwavelength spacing in a one-dimensional nanophotonic waveguide hold significant metrological potential due to strong dipole-dipole interactions. Analysis of the eigenmodes of the non-Hermitian Hamiltonian reveals ultra-narrow subradiant resonances, with the decay rate of the longest-lived state obeying a universal N⁻³ law with even-odd oscillations in the deep subwavelength regime. This pattern is observed in the single-photon scattering spectrum and allows detecting ultrasmall distance changes with sensitivity growing as N³. The quantum Fisher information reaches N⁶ and can be realized by measuring the spectral shift at the maximum slope of the subradiant resonance. The effect persists under realistic positional disorder, demonstrating the suitability of subradiance for quantum metrology. The work connects many-body waveguide quantum electrodynamics with high-precision sensing, paving the way to scalable quantum sensors on integrated nanophotonic platforms.
A chain of atoms on a light-guiding chip behaves like a row of pendulums on a shared support: swinging in opposite directions, they barely transfer energy to the air and freeze for a long time. When the distance between atoms becomes smaller than the wavelength of light (determined by the speed of light), they begin to collectively cancel each other's radiation. A subradiant—'quiet'—state emerges, in which the atoms seem to stop shining.
This silence is incredibly sensitive to the slightest shifts. Move one atom by just a thousandth of its size—and the silence turns into a sharp signal: the spectrum (the rainbow-like breakdown) of scattered light immediately distorts, and with precise measurement of brightness, a narrow dip appears. Remarkably, as the chain grows, sensitivity skyrockets: the lifetime of the quiet state increases proportionally to the cube of the number of atoms (N³). With a hundred atoms, you can detect a shift millions of times smaller than an atom.
The most surprising fact: even if the atoms are not arranged in a strictly periodic way, this collective silence proves remarkably robust. Moderate disorder only slightly dampens it but does not destroy it. Such nanophotonic rulers on a chip could become the basis for gravitational wave sensors or molecular contamination detectors.
🎯 Like an orchestra where musicians play out of phase and the hall falls silent, light from atoms can completely vanish due to mutual cancellation.
🎬 Such ruler chips resemble the tricorders from 'Star Trek'—miniature matter scanners.