Proposal For Generating The N-qubit GHZ State Based On The Cavity QED System

Quantum Information Science (QIC) is a new research area combining quantummechanics and classical information theory, casuing revolutionary advances in fields ofscience ande engineering involving computation, communication, precisionmeasurement, and fundamental quantum science.Quantum entanglement is one of the most striking features of quantum physics. Itnot only can be used to test basic problems in quantum mechanics, but also is a potentialresource for quantum information processing. In fact, most quantum informationprocessing is the quantum entangled states processing. So generation of quantumentangled states is becoming a basic work of the QIC. In the last10years, generationquantum entangled states have attracted a lot of eyes. By now, many schemes usingcooled-atoms, ions, photons, for generating entangled states have been proposed andexperimental realizations of entangled states have alse been reported for two atoms, tenbeams, fourteen photons.This paper focuses on the generation of multi-qubit GHZ states. As far as now,many useful schemes on generatin GHZ states have been proposed in ion trap, linearityoptics device, semiconductor quantum dot, nuclear magnetic resonance (NMR).Compared with these proposals, our scheme use superconducting flux qubit-macrowavecavity combined system, have the advantages of scalable, strong coupling, immune tothe fluctuation of the charge, individual addressing, controllable. The main content ofthis dissertation consists of three parts.In the first part, we introduce the basic concept and application of quantuminformation, quantum entanglement.In the second part, we make a brief introduction of the superconducting physicshistory. We list the configuration and quantum proposal of the Josephson devices, andthen we use the method to study the structure, feature, and control of thesuperconducting flux qubit as an example.In the third part, according to the theory background introduced above, we proposea scheme using three-level-type superconducting flux qubits combined withmicrowave cavity system to generate N-qubit GHZ entangled state. In our scheme, weplaced three-leve-type superconducting flux qubit into high Q macrowave cavity,introduced the process of single quantum gate and multi quantum gate. Then wegenerated N-qubits superconducing flux GHZ state with these gates. Because we usedmulti-qubits phase gate, our scheme is more brevity and effective.