Topological sensing of superfluid rotation using non-Hermitian optical dimers

TL;DR

This paper proposes a nondestructive, topological sensing scheme for superfluid rotation using a non-Hermitian optical dimer with an exceptional point, enabling robust detection via eigenmode permutation.

Contribution

It introduces a novel topological sensing method leveraging exceptional points in a non-Hermitian optical system coupled to a superfluid, enhancing robustness against noise.

Findings

The system exhibits a tunable exceptional point influenced by atomic response.

Eigenmode permutation at the exceptional point enables superfluid rotation sensing.

The proposed sensing method is intrinsically nondestructive and preserves superfluid coherence.

Abstract

We theoretically investigate a non-Hermitian optical dimer whose parameters are renormalized by dispersive and dissipative backaction from the coupling of the passive cavity with a ring-trapped Bose-Einstein condensate. The passive cavity is driven by a two-tone control laser, where each tone is in a coherent superposition of Laguerre-Gaussian beams carrying orbital angular momenta $\pm \ell \hbar$. This imprints an optical lattice on the ring trap, leading to Bragg-diffracted sidemode excitations. Using an exact Schur-complement reduction of the full light-matter dynamics, we derive a frequency-dependent self-energy and identify a static regime in which the atomic response produces a complex shift of the passive optical mode. This renormalized dimer supports a tunable exceptional point, enabling spectroscopic signatures in the optical transmission due to a probe field, which can in turn be utilized for estimating the winding number of the persistent current. Exploiting the associated half-integer topological charge, we propose a digital exceptional-point-based sensing scheme based on eigenmode permutation, providing a noise-resilient method to sense superfluid rotation without relying on fragile eigenvalue splittings. Importantly, the sensing proposals are intrinsically nondestructive, preserving the coherence of the atomic superfluid.