Extensive mixed-state entanglement in kinetically constrained superradiance

TL;DR

This paper demonstrates that adding local kinetic constraints to Dicke superradiance enables extensive mixed-state entanglement and the creation of long-range entangled dark states, with potential experimental realization.

Contribution

It introduces a method to generate extensive mixed-state entanglement in superradiant systems via local kinetic constraints, expanding the scope of entangled dark state preparation.

Findings

Analytically derived lower bounds for emission rate with kinetic constraints.

Identified exponentially many long-range entangled dark states.

Proposed experimental setups and witnesses for entanglement detection.

Abstract

Dicke superradiance by an ensemble of quantum emitters produces a collective burst of radiation, but no entanglement in the mixed state of the emitters. We show that adding a local kinetic constraint between the emitters generates extensive mixed-state entanglement, while otherwise preserving all key features of Dicke superradiance. Specifically, for any local Boolean constraint, we analytically derive a lower bound for the emission rate which implies a peak intensity $\propto N^2$ and a peak time $\propto (\log N)/N$ with number of spins $N$. This effect enables the superradiantly accelerated preparation of entangled dark states. Hereby, Hilbert-space fragmentation of the Dicke ladder leads to an exponentially branching decay tree that generates a hierarchy of dark states. Importantly, these disconnected manifolds include exponentially many long-range entangled singlet dark states. The explored kinetic constraints and superradiant dynamics can be realized in neutral-atom arrays coupled to an optical cavity, and we suggest a simple and accessible witness to detect the predicted mixed-state entanglement in such experiments. Moreover, we show that entanglement generation is robust against atomic decay and collective dephasing, and should be observable under recently reported experimental conditions. Our results, thereby, offer a general framework and experimentally viable approach for the dissipative engineering of entangled dark states enhanced by superradiance.