Classical-Quantum Correlation And Quantum Decoherence

Quantum mechanics has contributed a lots to our nature since it is founded. It exploits many new technical fields as well as explaining many phenomenons and facts in microscopic world. The relation between the quantum physics and the classical physics has been a hot research field. People have been debating how to understand the concepts and the basic principles of the quantum mechanics and whether the quantum mechanics is a complete theory since its start for the reason that quantum mechanics explains the world with a method quite different to the classical physics. The most famous controversies are the EPR oppugnation and the Schrodinger-cat oppugnation. They acutely criticize the concepts and the basic principles of the quantum mechanics.Some people including Einstein considered that the quantum mechanics was incomplete and self-contrary. Their main argument is the theory of local realism from which Bell obtained the famous Bell's inequality to test the quantum mechanics by experiments. Bell's inequality is based on two main assumptions-realism and locality. Recently some people conclude that the violation of the quantum mechanics to the Bell's inequality is due to the contradict ion between the locality and the quantum mechanics by studying a two qubits system and a three qubits system. In this thesis we generalize the conclusion into the case for many qubits and find it is also correct for multiparticle system. We also give the corresponding Bell-type inequalities in which there is a necessary condition for the separability of multiparticle states.The Schrodinger-cat oppugnation and the localization of macroscopic objects oppugn mainly the superposition states in quantum mechanics. Why the macroscopic objects have no the quantum coherence and how the quantum coherence disappears? People have tried to solve the problems and find that the theory of...