Quantum Coherence And Its Regulation Research

The coherent superposition of states, represents one of the most fundamental features that mark the departure of quantum mechanics from the classical realm. Quantum coherence in many-body systems embodies the essence of entanglement and is an essential ingredient for a plethora of physical phenomena in quantum optics, quantum information, solid state physics, and nanoscale thermodynamics. In recent years, research on the presence and functional role of quantum coherence in biological systems has also attracted a considerable interest. Despite the fundamental importance of quantum coherence, the development of a rigorous theory of quantum coherence as a physical resource has only been initiated recently. Based on the framework of the resource theory of quantum coherence, the problem about the resource theory of quantum coherence becomes a hot physics problem in today. Due to the properties of quantum coherence and its extensively possible application in a wide variety field, it is meaningful to study the theory and application of the resource theory of quantum coherence. In this thesis we review and discuss the development of this research field that encompasses the characterization,quantification, dynamical evolution, and manipulation of quantum coherence. The main results of this thesis are as follows.1. We give a comprehensive overview of recent developments to construct a resource theory of quantum coherence. Focuses on the plethora of applications and operational interpretations of quantum coherence to thermodynamics, quantum information and quantum metrology, concludes a hierarchy of possible classes of incoherent operations, presents a compendium of recently proposed monotones and measures of quantum coherence, based on different physical approaches endowed with different mathematical properties, in single and multipartite systems.Based on the four basic conditions and the three additional conditions to which any valid coherence quantifier should abide, we conclude that the relative entropy and the l1 normal of coherence are valid quantifier in the field of quantum information.2. We discuss the coherence of a single quantum system converting to nonclassical correlations. Firstly, we analyze the two necessary conditions when a product system becomes an entangled system under incoherent operations, namely, the initial state of control qubit is coherent state and the target qubit is not the maximally coherent state, the conditions of the coherence consumption are its values always positive. Secondly, we analyze the two necessary conditions when a product system becomes a correlated system under incoherent operations, the conditions of initial state is identical to the above, the conditions of the coherence consumption are its values always nonegative. And we also discuss the conditions to prepare an entangled quantum state and a correlated quantum state under incoherent operation.3. We discuss the relations among quantum coherence, quantum entanglement and quantum discord in a mutipartite quantum system. After calculation and analysis, we find for the measures of coherence, entanglement and quantum discord based on the distance of relative entropy there always exist the relation, C(?) ? D(?) ? E(?), but for the measures of coherence, entanglement and quantum discord in a different way, the relation is not true.4. We analyze the dynamical evolution of coherence of a quantum system in certain environment. We study the phenomenology of quantum coherence, entanglement and discord in the dynamical evolution of nondissipative markovian decoherence channel, and find their behavior are completely different, particular for the quantum coherence, the behavior of evolution is distinct for different coherence measures. We also study the phenomenology of quantum coherence, entanglement in the dynamical evolution of dissipative open quantum systems, and find the process of decoherence is the transference of coherence between different quantum systems, the weak measurement can influence the behavior of coherence evolution.5. We discuss the problem of freezing and protecting of quantum coherence when quantum system undergo decoherence channel, in terms of the method of protecting quantum entanglement. Using the quantum weak measurement and quantum measurement reversal, we study the methods of freezing and protecting of quantum coherence when a quantum system undergoes different nondissipative Markovian decoherence channel, and find that the coherence of quantum system is frozen and protected in a probability when the conditions of weak measurement or quantum measurement reversal are satisfied.