Probing photon correlations in the dark sites of geometrically frustrated cavity lattices

TL;DR

This paper investigates how weak photon interactions in frustrated cavity lattices can lead to finite photon populations and strong correlations at dark sites, revealing multiphoton states through theoretical analysis.

Contribution

It introduces a theoretical framework for understanding photon correlations at dark sites in frustrated cavity lattices with weak nonlinearities.

Findings

Dark sites acquire finite photon populations due to multiphoton states.

Photon correlations at dark sites are significantly enhanced.

Weak interactions can induce observable multiphoton effects in frustrated lattices.

Abstract

We theoretically explore the driven-dissipative physics of geometrically frustrated lattices of cavity resonators with relatively weak nonlinearities, i.e. a photon-photon interaction smaller than the loss rate. In such systems, photon modes with zero probability at 'dark' sites are present at the single-particle level due to interference effects. In particular, we study the behavior of a cell with three coupled resonators as well as extended Lieb lattices in 1D and 2D. By considering a partial pumping scheme, with the driving field not applied to the dark sites, we predict that even in presence of relatively weak photon-photon interactions the nominally dark sites achieve a finite photonic population with strong correlations. We show that this is a consequence of biphoton and multiphoton states that in the absence of frustration would not be visible in the observables.