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Physical Review E

Thermal entanglement in two-atom cavity QED and the entangled quantum Otto engine

Hao Wang, Sanqiu Liu, Jizhou He

Published Apr 8, 2009• 128 citations
Publisher

Abstract

The simple system of two two-level identical atoms couple to single-mode optical cavity in the resonance case is studied for investigating the thermal entanglement. It is interesting to see that the critical temperature is only dependent on the coefficient of atom-atom dipole-dipole interaction. Based on the mode, we construct and investigate a entangled quantum Otto engine (QOE). Expressions for several important performance parameters such as the heat transferred, the work done in a cycle, and the efficiency of the entangled QOE in zero G are derived in terms of thermal concurrence. Some intriguing features and their qualitative explanations are given. Furthermore, the validity of the second law of thermodynamics is confirmed in the entangled QOE. The results obtained here have general significance and will be helpful to understand deeply the performance of an entangled QOE.

DOI
10.1103/physreve.79.041113

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The simple system of two two-level identical atoms couple to single-mode optical cavity in the resonance case is studied for investigating the thermal entanglement. It is interesting to see that the critical temperature is only dependent on the coefficient of atom-atom dipole-dipole interaction. Based on the mode, we construct and investigate a entangled quantum Otto engine (QOE). Expressions for several important performance parameters such as the heat transferred, the work done in a cycle, and the efficiency of the entangled QOE in zero G are derived in terms of thermal concurrence. Some intriguing features and their qualitative explanations are given. Furthermore, the validity of the second law of thermodynamics is confirmed in the entangled QOE. The results obtained here have general significance and will be helpful to understand deeply the performance of an entangled QOE.
Abstract A scheme is theoretically proposed to investigate a quantum Otto engine (QOE) based on cavity quantum electrodynamics (QED) systems, where the working substance consists of a single‐mode optical cavity coupled to either one or two identical two‐level atoms, corresponding to the Jaynes–Cummings (JC) and Tavis–Cummings (TC) models, respectively. These results show that quantum coherence can enhance the efficiency of the quantum Otto heat engine (QOHE) and that the QOE can operate in various thermodynamic modes, such as a heat engine, refrigerator, or heater. Building on these two cavity QED models, it is further demonstrated that increasing the number of atoms leads to an exponential enhancement in the work output of the QOHE. Finally, a localized quantum engine is analyzed by tracing out one of the atoms in the TC model and show that the local system can achieve an efficiency comparable to that of the global system. This work establishes a novel theoretical framework for understanding and optimizing the performance of quantum heat engines in cavity QED platforms.
This paper establishes an entangled otto quantum heat engine(EQHE) working with the two-qubit anisotropic Heisenberg XXZ model.Based on the first law of quantum thermodynamics,we derive the expressions for the net work and the efficiency of EQHE.By numerical calculation we plot three dimensional graphics between the efficiency and the concurrence.It is found that the efficiency of the EQHE is smaller than the Carnot efficiency and the validity of the second law of thermodynamics is confirmed;The region of non-zero efficiency is mainly distributed in C1C2 and the value of efficiency and region of non-zero efficiency increase with the increase of the ratio of the temperature γ.The efficiency of the EQHE is discussed in two special cases Δ=0 and Δ=1.
Based on the isotropic two spin-1/2 qubits Heisenberg model with Dzyaloshinskii–Moriya interaction in a constant external magnetic field, we have constructed the entangled quantum Otto engine. Expressions for the basic thermodynamic quantities, i.e. the amount of heat exchange, the net work output and the efficiency, are derived. The influence of thermal entanglement on these basic thermodynamic quantities is investigated. Moreover, some intriguing features and their qualitative explanations in zero and finite magnetic field are given. The validity of the second law of thermodynamics is confirmed in the system. The results obtained here have general significance and will be useful in increasing understanding of the performance of an entangled quantum engine.
We theoretically propose and investigate a quantum Otto engine that works with a single-mode radiation field inside an optical cavity and is driven alternately by a hot reservoir and a cold reservoir. The hot reservoir is realized using a beam composed of thermally entangled pairs of two-level atoms that interacts resonantly with the cavity, and the cold reservoir is composed of a collection of noninteracting boson modes. In terms of the quantum discord of the pair of atoms, we derive analytical expressions for the performance parameters (i.e., power and efficiency) and the stability measure (the coefficient of variation of power). We show that nonclassical correlations boost the quantum engine's performance and efficiency, and they may even change the operation mode at specified values of the two bath temperatures. We also demonstrate that the nonclassical correlations improve the stability of the machine by reducing the coefficient of variation of power that satisfies the generalized thermodynamic uncertainty relation. Finally, we find that these results can be transferred to another quantum Otto engine model, in which the optical cavity is coupled alternately to a hot thermal bosonic bath and to a beam composed of pairs of the two correlated atoms that plays the role of a cold reservoir.
We developed a model of a quantum Otto engine using two dipole-coupled two-level atoms. Based on the platform, we focus on fundamental thermodynamic quantities, including heat absorption, release to heat baths, work done, and efficiency. The characteristic of the engine either for the case of identical as well as non-identical two two-level atoms is investigated under the influence of average frequency, frequency detuning, and coupling strength. The conditions for the efficiency to be higher than in the noninteracting case are found. A tighter upper bound for the efficiency is found, which is lower than the Carnot limit. The second law of thermodynamics holds all the while. Our findings represent a step forward in the design of quantum thermodynamic devices, which take advantage of quantum resources.
Based on a two-qubit one-dimensional isotropic spin-1∕21∕21∕2 Heisenberg spin chain in a constant external magnetic field, we construct a four-level entangled quantum heat engine (QHE) and investigate the influence of entanglement between two qubits on basic thermodynamic quantities, i.e., the heat transferred and the work done in a cycle, and the efficiency of the QHE. The validity of the second law of thermodynamics is confirmed in the entangled system. We also find several interesting features of the variation of the efficiency with the entanglement of two different thermal equilibrium states in a work cycle in zero and finite magnetic field. An abrupt transition of efficiency is found in zero field.