Preparation Of Entangled States In Superconducting Qubits

As a new interdisciplinary subject, quantum information has achieved a rapid development in the past twenty years. It has been demonstrated to gain great advantages in some certain areas, and its potential application may be plentiful. Quantum entanglement is regarded as the most amazing property of quantum mechanical, and is also an important resource in quantum information processing. Among various of physical systems developed for quantum information processing, superconducting qubits are regarded as promising candidates because of its flexibility and scalability. This thesis is mainly focused on generation of entangled states in superconducting qubits. In this thesis we propose several schemes for preparation of entangled states in superconducting qubits. The main works are as follows:We propose a scheme for generation of GHZ states and quantum phase gates in superconducting qubits. The scheme uses the resonant interaction and work in a fast way.We propose a scheme to generate Bell states in a pair of coupled superconducting charge qubit and flux qubit. In the scheme two qubits work in their degenerate points, so they are insensitive to the fluctuations of the environment.Based on the system in which superconducting qubits are coupled to a superconducting transmission line resonator, we propose a scheme to generate GHZ states of N qubits and W states of three qubits. In the scheme, the initial states of the qubits can be easily prepared. During the scheme the cavity is virtually excited, so it is insensitive to cavity decay. We also propose a scheme to generate cluster states of N qubits. In the scheme the qubits work in their degenerate points, so they have a long decoherence time. Our scheme is insensitive to the cavity's initial state, and we obtain the cluster states in only one step.