Superradiance — the collective spontaneous emission of light from an ensemble of atoms — is typically analyzed at the mean-field level, where atoms are treated as identical classical dipoles radiating in phase. A cross-cavity system with four-level atoms coupled to two perpendicular cavities achieves steady-state superradiance through purely dissipative dynamics, with one cavity mediating collective decay and the other providing collective pumping via an off-resonant Raman transition. The resulting steady state exhibits super-Poissonian photon statistics — more photon bunching than a thermal source — demanding analysis beyond mean field.
The essential physics: superradiant decay kicks atoms along the cavity axis, and this recoil creates entanglement between spin and motional degrees of freedom. The light emission process, rather than being a one-way loss channel, weaves correlations between what the atoms are doing internally and how they are moving. Dissipation generates entanglement instead of destroying it. Measurements on the cavity output can then prepare states with substantial particle-particle entanglement useful for quantum-enhanced acceleration sensing.
The structural claim is counterintuitive and precise: collective loss channels — processes that remove energy from a system — can be the mechanism that creates quantum correlations. Entanglement does not require coherent driving or careful unitary gates. It can emerge from the geometry of how a system decays.
(arXiv:2603.00463)