Exponentially enhanced sensing through nonreciprocal light propagation

TL;DR

This paper demonstrates an optical sensor leveraging non-reciprocal light propagation to achieve exponentially enhanced detection sensitivity, utilizing coupled Hatano-Nelson chains within an electro-optic frequency comb.

Contribution

It introduces a novel non-Hermitian sensing method based on non-reciprocal propagation in coupled HN chains, enabling exponential SNR scaling with system size.

Findings

SNR scales exponentially with the number of frequency modes.

Achieved sensing with up to 70 frequency modes per chain.

Potential applications in remote sensing and superconducting circuit readout.

Abstract

Non-reciprocity is a key resource for pushing the performance of photonic devices beyond the fundamental limits imposed by Lorentz reciprocity. Here, we report on the realization of an optical sensor where non-reciprocal light propagation allows detecting small perturbations with a signal-to-noise ratio (SNR) that scales exponentially with system size. Our approach is based on encoding two Hatano-Nelson (HN) chains, which is equivalent to the bosonic Kitaev model, within the resonant modes of an electro-optics frequency comb. Non-reciprocal light propagation in the frequency domain is realized through simultaneous phase and amplitude modulation of the circulating field inside the optical fiber cavity. We demonstrate the sensing of a small modulating tone coupling the two HN chains with a SNR that scales exponentially with the lattice size, formed from up to 70 frequency modes per chain. Our results open a new paradigm in non-Hermitian sensing, with potential applications in remote sensing including the optical readout of superconducting circuits.