Article

Entangled quantum heat engines based on two two-spin systems with Dzyaloshinski-Moriya anisotropic antisymmetric interaction

The European Physical Journal D (Impact Factor: 1.4). 08/2008; 49(1):123-128. DOI: 10.1140/epjd/e2008-00133-0
Source: arXiv

ABSTRACT We construct an entangled quantum heat engine (EQHE) based on two two-spin systems with Dzyaloshinski-Moriya (DM) anisotropic
antisymmetric interaction. By applying the explanations of heat transferred and work performed at the quantum level in Kieu’s
work [Phys. Rev. Lett. 93, 140403 (2004)], the basic thermodynamic quantities, i.e., heat transferred, net work done in a cycle and efficiency of EQHE
are investigated in terms of DM interaction and concurrence. The validity of the second law of thermodynamics is confirmed
in the entangled system. It is found that there is a same efficiency for both antiferromagnetic and ferromagnetic cases, and
the efficiency can be controlled in two manners: (1) only by spin-spin interaction J and DM interaction D; (2) only by the temperature T and concurrence C. In order to obtain a positive net work, we need not entangle all qubits in two two-spin systems and we
only require the entanglement between qubits in a two-spin system not be zero. As the ratio of entanglement between qubits
in two two-spin systems increases, the efficiency will approach infinitely the classical Carnot one. An interesting phenomenon
is an abrupt transition of the efficiency when the entanglements between qubits in two two-spin systems are equal.

0 Bookmarks
 · 
62 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We consider a single quantum mechanical particle confined to an one-dimensional (1D) infinite square well, and propose a nonequilibrium quantum Otto cycle (NQOC). Compared with the conventional quantum Otto engine (CQOE) investigated by [T.D. Kieu, Phys. Rev. Lett. 93, 140403 (2004); T.D. Kieu, Eur. Phys. J. D 39, 115 (2006)], due to the effects of negentropy produced in the NQOC, many interesting features appear: (1) in general, the NQOC is capable of extracting more work, so it is more efficient; (2) the NQOC can operate even when T 1 = T 2 or T 1< T 2, where T 1 (T 2) represents the temperature of hot (cold) bath; (3) in some cases, the NQOC can absorb heat from both baths and completely transforms them into work. These results demonstrate that the negentropy can be understood as an effective source of efficiency in quantum heat engines (QHEs) and meanwhile it is shown that the second law of thermodynamics is not violated. At last, we also show that the efficiency of NQOC reduces to that of classical Otto cycle in the classical limit.
    The European Physical Journal D 07/2013; 67(7). · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The four-level entangled quantum refrigerator (QR) is studied in the XXZ Heisenberg model for the two-qubits. The Hamiltonian of the problem includes the exchange parameters Jx = Jy = J and Jz = αJ along the x-, y- and z-directions, respectively, and constant external magnetic field B in the z-direction. The parameter α is introduced into the model which controls the strength of the exchange parameter Jz in comparison to Jx and Jy, thus, our investigation of QR includes the XX (α = 0.0), XXX (α = 1.0) and XXZ (for other α's) Heisenberg models. The two-qubits are assumed to be in contact with two heat reservoirs at different temperatures. The concurrences for a two-qubit are used as a measure of entanglement and then the expressions for the amount of heat transferred, the work performed and the efficiency are derived. The contour, i.e., the isoline maps, and some two-dimensional plots of the above mentioned thermodynamic quantities are illustrated.
    International Journal of Modern Physics B 05/2013; 27(13):50055-. · 0.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Based on a two-qubit isotropic Heisenberg XXX model with a constant external magnetic field, we construct a four-level entangled quantum heat engine (QHE). The expressions for several thermodynamic quantities such as the heat transferred, the work and efficiency are derived. Moreover, the influence of the entanglement on the thermodynamic quantities is investigated analytically and numerically. Several interesting features of the variation of the heat transferred, the work and the efficiency with the concurrences of the thermal entanglement of different thermal equilibrium states are obtained.
    Science China: Physics, Mechanics and Astronomy 10/2012; 55(10). · 0.86 Impact Factor

Preview

Download
1 Download
Available from