Weak Measurement And Its Applications In State Discrimination

Quantum information and quantum computation are born in1980’s,which were new inter-disciplinary subjects of quantum mechanics and the science of computation and communica-tion. As the development of quantum information and quantum computation, people found great advantages of quantum communication and more efficiency by quantum computation,compared with classical mode.Chapter1will review the history and basic principle of quantum mechan-ics,and also present a brief introduction to quantum information and computation.In the quantum information field, information is usually encoded in and carried by quantum states, a key step is to discriminate each of the encoded states. The higher the rate of success and accuracy of discrimination is, the more information can be gained from the encoded states and higher precision for operations on the quantum system. So, Chapter2will give a presentation for state discrimination.In Chapter3, we will review some theoretical works about quantum weak measurement, and subsequently in Chapter4, we will introduce our works beyond the original weak meausurement formalism.In Chapter5, we will focus on the unambiguous discrimination of pure quantum states. We propose a method to discriminate two extremely similar quantum states via a weak measurement. For the two states with equal prior probabilities, the optimum discrimination probability given by Ivanovic-Dieks-Peres limit can be achieved by our protocol with an appropriate choice of the interaction strength. However, compared with the conventional method for state discrimination, our approach shows the advantage of error-tolerance by achieving a better ratio of the success probability to the probability of error.