Study Of The Symmetric Quantum Discord For The Two-qubit Quantum Systems

ABSTRACT:As we know, quantum measurements is very important for quantum information, and also quantum measurements is one of the fundamental problems for quantum physics. So, in this thesis, we care about the quantum measurements. If we want to study quantum measurements, we have to find the quantum correlations in a quantum system, so we have discussed the definition of quantum correlation, and introduce how to calculate the quantum correlation. In this thesis, we focus on two measures methods, quantum discord and symmetric quantum discord.We discuss the quantum discord for some states, such as Bell diagonal states, two qubit X states, a general two qubit states, and the Gaussian states.We discuss the symmetric quantum discord for an arbitrary two-qubit state consisting of subsystem A and B and give the analysis formula of symmetric quantum discord for an arbitrary two-qubit state. We also give the optimization process of the symmetric quantum discord for some states and obtain the symmetric quantum discord. We compare the quantum discord with symmetric quantum discord, and find that symmetric quantum discord is greater than quantum discord. We also find that the symmetric quantum discord can be unequal to the quantum discord when the right quantum discord (measure on subsystem B) is equal to the left quantum discord (measure on subsystem A)...