Generation Of Singlet States Based On Ion-trap System And Fiber-coupled Cavity System

Quantum information science, which came into being in the 1970s, is a new interdisciplinary field derived from the combination of quantum mechanics and information science. As one of the most attractive frontiers, quantum information science has become the research focus of the international academic community. Its potential application and great scientific significance will bring about unpredictable impact for the human. Quantum entanglement with the unique characteristic of nonlocality correlation, has become an important physical resource in quantum information processing and has been widely applied. As the dimension of the quantum entanglement increases, the information capacity is also gradually increased. So the high-dimension quantum entanglement possesses stronger nonlocality and ability of quantum information processing. High-dimension entangement can increase the security of quantum crytography protocols and improve the efficiency of implementing quantum logic gates. In recent years, how to effectively prepare high-dimension entangled states has caused more and more attention. The preparation of Singlet states, which is a kind of important high-dimension entangled states, also has aroused people’s great interest.At present, people research quantum information processing mainly in cavity QED, optical system, ion-trap system, nuclear magnetic resonance, quantum dots, and so on. Cavity QED and ion-trap system, as two very important physical systems, play a significant role in quantum information science. Therefore, my master’s degree thesis is about generation of Singlet states in ion-trap system and fiber-coupled cavity QED system.The main work of this paper are as follows:1. In the ion-trap system, we present a scheme for preparation of three-ion singlet state via stimulate Raman adiabatic passage and fractional stimulate Raman adiabatic passage. First, the second and third ions are drived by two different classical fields, then we can obtain the maximally entangled state of the two ions. Second, the three ions are drived by two different classical fields. Finally, we prepare the three-ion Singlet state via adiabatic evolution.2. A scheme is proposed for the generation of three-atom Singlet state in the fiber-coupled cavity QED system. The distinctive feature of the scheme is that the three atoms are respectively trapped in different cavities. First, the cavity modes and the fiber modes are initial in vacuum state, and via the quantum Zeno dynamics the system evolves in a Zeno subspace without exciting the cavity modes and fiber modes. Thus, our scheme is insensitive to the cavity decay and the dissipation of the fibers. Then, we make ues of the large detuning condition to prepare the three-atom Singlet state, and the excited states of the atoms can be adiabatically eliminated. As a result, our scheme obtains a relatively high fidelity.