Nonclassical Many-Body Superradiant States with Interparticle and Spin-Momentum Entanglement

TL;DR

This paper introduces a novel cross-cavity system achieving steady-state superradiance through collective dissipative dynamics, resulting in nonclassical states with spin-momentum entanglement and potential quantum sensing applications.

Contribution

The work develops an exact master equation simulation for a complex cavity-atom system, revealing nonclassical superradiant states with hybrid entanglement beyond mean-field models.

Findings

Steady-state superradiant states with super-Poissonian photon statistics.

Significant spin-momentum entanglement at steady state.

Heralded measurements enable particle entanglement for quantum sensing.

Abstract

We present a cross-cavity system in which steady-state superradiance is achieved using solely collective dissipative dynamics. Two cavities symmetrically couple an ensemble of four-level atoms by driving transitions between two electronic states and two motional states along perpendicular cavity axes. Both cavities operate in the bad-cavity regime: one cavity mediates collective atomic decay, while the other cavity, together with a coherent drive, mediates collective pumping via an off-resonant Raman transition. With this, we find steady-state superradiant states that possess nonclassical properties, such as super-Poissonian photon statistics. The system thus requires a beyond mean-field description, and so we develop an exact master equation simulation technique utilizing strong symmetries of the system's jump operators. Because superradiant decay is accompanied by a momentum impulse along the corresponding cavity axis, the system exhibits substantial hybrid entanglement between the atoms' spin and motional degrees of freedom at steady state. We also demonstrate that heralded measurements of the two cavity outputs prepare a state with significant particle-particle entanglement with prospects for quantum-enhanced acceleration sensing.