Quantum Coherencebased Researches on Thermal Phenomena of Macroscopic System 

Author  ZhangZuo 
Tutor  LiChengZu 
School  National University of Defense Science and Technology 
Course  Physics 
Keywords  Quantum coherence Quantum entanglement Quantum heat engine Thermal entanglement Quantum phase transitions Entanglement logo Inequivalent entangled logo 
CLC  O431.2 
Type  PhD thesis 
Year  2008 
Downloads  72 
Quotes  0 
Quantum coherence is the core of quantum mechanics, which describes a quantum system several different pure state superposition into a situation. Equivalent subsystem is in several different states coherent superposition state, if the state does not destroy the system, it is impossible to determine exactly which state quantum system on. Quantum entanglement is a special (complex systems) coherent superposition state. Quantum information technology, in essence, is the use and development of coherent superposition of quantum states, entanglement and other nonclassical properties, information storage, transmission and processing. Heat is the study of macroscopic systems and thermal phenomena associated with various heat of the discipline. Backtracking thermal development process, thermodynamics and the combination of atomic and molecular theory leads to the generation of statistical physics, when describing the microscopic theory of particle motion in the development from classical mechanics to quantum mechanics, quantum statistical theory is formed. Each time the introduction of new ideas have deepened the understanding of human macroscopic systems. With the quantum coherence and quantum entanglement increasingly extensive and indepth research, quantum coherence and quantum entanglement phenomenon is not only on a macroscopic scale can be achieved, and originally thought confined to the microscopic world of quantum entanglement experiments in recent years have found that macroscopic systems can The nature of produce observed. Therefore, we should continue to study the thermodynamic properties of macroscopic systems, it will be necessary coherence of quantum states introduced into the theory of thermal systems in the past. After the introduction of quantum coherence, study the thermal phenomena and macroscopic systems associated with the various laws of heat, not only to further develop the thermal improvement, and is expected to deepen the understanding of quantum coherence, to solve some of the fundamental problems of quantum mechanics, but also may be practical quantum information technologies play a fundamental role in guiding. This article consists of the following: (a) studies of quantum heat engine. First, the introduction and indepth study of a working material for the twolevel system of quantum heat engine model clarifies TDKieu text \at an average sense only correct \This proves that quantum heat engine can work outside, the second law of thermodynamics is always valid. Second, for the first time in the study of quantum heat introduced entanglement. Construct a fourlevel model of the heat engine, the working substance is intertwined two twolevel quantum system consisting of fourlevel system. The effects of heat engine heat, external work and the relationship between efficiency and entanglement prove the second law of thermodynamics entangled in a system containing remains correct. The effects of quantum heat engine can work outside conditions, and found no entanglement of twolevel quantum heat engine, compared with the fourlevel quantum entanglement heat relaxes the temperature, magnetic field and other control parameters of the request. (2) on the thermal properties of entanglement. Thermal Entanglement is a system in thermal equilibrium entanglement contained. First, the effects of a specific Heisenberg spin chain entanglement with temperature, magnetic field parameters characteristics. Through the analysis of eigenstates and accurate explanation of these characteristics. Second, based on Heisenberg spin chain eigenstates characteristics, summarized the Heisenberg spin chain entanglement of three general characteristics, for any length of Heisenberg spin chain of arbitrary nbody entanglement, are generally established . (3) identification of nonequivalence of entanglement. For the first time explicitly put forward the concept of nonequivalent entanglement logo expounded identified two inequivalent entanglement points. Magnetization can be used as absolute proof of Heisenberg spin chain eigenstates unequal struggle logo. (4) of quantum phase transitions and quantum entanglement is not equivalent to the link between research categories. The first to investigate the quantum phase transition and the ground state entanglement links between unequal classification. We believe that the sub phase transition occurs, the ground state entanglement type also changed, and for the onedimensional Heisenberg spin chain and XY spin model, verify this speculation.