Research Of Quantum Information Processing Via Superconducting Quantum Interference Device In Cavity Qed

Quantum information science is a combination of quantum mechanics and information science. Quantum theory is not only a theory on atoms and sub-atoms, but also a completely new idea of the world. It brings new development and applications for information science.At present, several kinds of physical hardware have been designed to achieve quantum information processing, among which, cavity quantum electrodynamics (Cavity QED) is considered one of the most promising hardware systems. Due to the limitations on the control of microscopic-particles, it is believed that solid-state devices are more likely employed to achieve large-scale quantum computing. Superconducting quantum interference devices (SQUIDs) have been demonstrated to be easy to scale up and have long de-coherence time. By embedding them in cavities, one can easily achieve strong coupling between SQUID and cavity or between SQUIDs, immunity to noises and suppression of spontaneous emission. Because of these advantages, the SQUID-cavity system increasingly becomes the important research topic.Quantum cloning and quantum algorithms are two important topic in quantum information processing, this thesis mainly carries out the following researches: 1) Propose a scheme for realizing probabilistic cloning of superconducting quantum interference device qubits in a cavity ; 2) Propose a scheme for realizing Deutsch–Jozsa quantum algorithm with superconducting quantum interference device qubits in a cavity. In the first research, with two SQUIDs embedded in a high-Q cavity used as the original and target qubits respectively, and the cavity field as the measurement qubit, the unitary evolution required for the cloning machines is realized through multiple interactions of SQUID with the cavity or classical microwave pulses. Then the state reduction is implemented by mapping the cavity state onto another SQUID and measuring the magnetic flux of the SQUID, thus realizing the exact cloning of quantum states with optimal success probability. In this scheme, two–photon Raman resonance process is used to increase the operation rate, and the total operation time is far less the time of spontaneous decay and cavity decay. Therefore this scheme is experimentally feasible. In the second research, a physical scheme was proposed for implementing Deutsch-Jozsa algorithm, with SQUIDs used as qubits and drived by cavity and classical microwave pulses. This scheme can be generalized to multi-qubit case and can be used to demonstrate the advantage of parallel computation of quantum computers. In this scheme, information is stored in two stable low energy levels of SQUID and large detuning interaction of SQUID–cavity is employed, therefore spontaneous radiation and the leakage off the cavity are effectively suppressed.