Dissertation > Mathematical sciences and chemical > Physics > Optics > The light nature of the theory > Quantum optics

Quantum Coherence-based 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
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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 non-classical 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 in-depth 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 in-depth study of a working material for the two-level 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 four-level model of the heat engine, the working substance is intertwined two two-level quantum system consisting of four-level 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 two-level quantum heat engine, compared with the four-level 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 n-body entanglement, are generally established . (3) identification of non-equivalence of entanglement. For the first time explicitly put forward the concept of non-equivalent 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 one-dimensional Heisenberg spin chain and XY spin model, verify this speculation.

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