Entanglement driven self-organization of a quantum gas in a cavity field

Full text: Laser-driven particles moving in the optical lattice potential of a high-Q cavity field can undergo a transition from a spatially homogeneous to an ordered phase. We extend the theoretical analysis of the bistable self ordering to the zero temperature quantum regime. The entanglement between the particles and the field creating the potential is proved to be essential for the onset of self ordering. At a quantum level, it allows a fast decay of the homogeneous atomic cloud into an entangled superposition of the two stable ordered configurations and the field. This should be generic for a wide class of quantum phase transitions, whenever the quantum state of the system (order parameter) acts back on the controlling potentials. (author)