Collapse of Entangled State and Entropy Increase in an Isolated System

Qiren Zhang

Jenny Hide, Vlatko Vedral

Qiren Zhang

We show that the collapse of the entangled quantum state makes the entropy increase in an isolated system. The second law of thermodynamics is thus proven in its most general form.

Dominik Janzing

Song Jun, Zhuo‐Liang Cao

In this article,the time evolution properties of the field entropy in the system of the two identical two-level entangled atoms interacting with the single-mode coherent light field are studied by means of full quantum theory.The influences of the initial states and the degree of entanglement of two identical two-level entangled atoms and the intensity of the light field on the field entropy are discussed by numerical calculations.The results show that the average value and the oscillation frequency of the field entropy increases with the increasing of the mean photon number,the oscillation of the field entropy presents stated periods in the weak light field and presents collapses and revivals in the increased light field,the amplitudes of field entropy increase with increasing initial degree of entanglement of two entangled atoms.

C. M. Lóbez, Armando Relaño

We study nonequilibrium processes in an isolated quantum system-the Dicke model-focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy.