Quantum thermalization through entanglement

David A. Huse

Li‐Bao Fan, Yue‐Hui Zhou, Fen Zou +3 more

Abstract The quantum thermalization of the Jaynes–Cummings (JC) model in both equilibrium and non‐equilibrium open‐system cases is studied, in which the two subsystems, a two‐level system and a single‐mode bosonic field, are in contact with either two individual heat baths or a common heat bath. It is found that in the individual heat‐bath case, the JC model can only be thermalized when either the two heat baths have the same temperature or the coupling of the JC system to one of the two baths is turned off. In the common heat‐bath case, the JC system can be thermalized irrespective of the bath temperature and the system–bath coupling strengths. The thermal entanglement in this system is also studied. A counterintuitive phenomenon of vanishing thermal entanglement in the JC system is found and proved.

Prasenjit Deb, Abhishek Banerjee, Pratapaditya Bej +1 more

Tsung-Cheng Lu, Tarun Grover

The authors find that the entanglement between two subsystems in tripartite quantum states can reveal novel aspects of quantum thermalization. In particular, it can probe the presence or absence of long-lived quasiparticles. Systems without quasiparticles exhibit an ``entanglement transition'' from area to volume law as one tunes the subsystem volume fraction within a single representative state, a feature invisible in conventional schemes based on bipartite entanglement. Such a transition is absent in systems with quasiparticles.

Tanmay Saha, Pratik Ghosal, Pratapaditya Bej +2 more

Wang‐Yan Liu, Li‐Bao Fan, Ye‐Xiong Zeng +2 more

Abstract Quantum thermalization and thermal entanglement in the open quantum Rabi model (QRM), in which a two‐level system and a single‐mode bosonic field are coupled to either two individual heat baths or a common heat bath, are studied. By treating the QRM as an effective multilevel system and deriving global quantum master equations in the eigenstate representation of the QRM, the physical conditions for quantum thermalization of the QRM is studied. It is found that, in the individual heat‐bath case, the QRM can only be thermalized when either the two heat baths have the same temperature or the QRM is only coupled to one of the two baths. In the common heat‐bath case, differently, the QRM can always be thermalized. Thermal entanglement of the QRM in both the resonant‐ and non‐resonant coupling cases is also studied. The logarithmic negativity for the thermal state of the QRM is obtained in a wide parameter space, ranging from the low‐ to high‐temperature limits, and from the weak‐ to deep‐strong‐coupling regimes. This work paves the way toward the study of quantum effects in nonequilibrium ultrastrongly‐coupled light‐matter systems.