What it is
In Dicke superradiance, an ensemble of quantum emitters releases a collective burst of light, but leaves the emitters' mixed state unentangled. The authors show theoretically that adding a local kinetic constraint between the emitters (in their preprint, a Rydberg blockade or anti-blockade that lets an atom couple to the cavity only depending on the state of its neighbours) generates extensive mixed-state entanglement while preserving all the key features of superradiance. For any local kinetic constraint they derive a lower bound on the emission rate implying that the peak intensity still grows as the square of the number of spins, N², and the peak time still shrinks as (log N)/N. Fragmentation of the ladder of states the decay runs down makes it branch exponentially into a hierarchy of dark states, which include exponentially many long-range entangled singlet dark states, so superradiance speeds up the preparation of entangled dark states.
Why it matters
Superradiance on its own leaves atoms unentangled; a local constraint turns that fast burst into a way of preparing entangled states. The authors propose realising it in neutral-atom arrays coupled to an optical cavity, a combination the preprint notes has just been demonstrated, and suggest a simple witness to detect the entanglement: in the preprint, a count of adjacent excited pairs, which is zero for any unentangled dark state. They report that the entanglement generation is robust against atomic decay and collective dephasing and should be observable under recently reported experimental conditions; in a preprint simulation of a short chain, at the cooperativity recent cavity experiments reach, the transient entanglement peaks at 62% of its lossless value.
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Filed underQuantum optics and atomic interactions, Strong Light-Matter Interactions, Quantum Information and Cryptography
