Study On Cavity-Qed Scheme In Quantum Information

Quantum information science is a rapidly growing brand-new interdisciplinary science subject with a wide and profound future application field. Since the carrier of information in this subject is quantum state, all the problems related to information should be resolved by means of quantum theory. Therefore, quantum information science exhibits a number of advantages corresponding to its classical counterpart.In the past few years,cavity-QED as a candidate has been attracting much attention.The interaction between atoms and photons has reached what is called strong-coupling range in optical cavity. In this case, an entangled atom-photon-cavity system is established and this very novel system is widely used for quantum information science, such as quantum state preparation, quantum communication and quantum computation, etc. With the development of the cavity-QED experiment, we should find new theoretical scheme to quantum information processing. There are four main parts in this thesis:First we present the basic conception and the recent experimental development in cavity-QED.We get the Hamiltonian of the interaction between the atom and the radiation field through the method of field quantization. Then we give an overview of the cavity-QED experiments setups.Secondly we study on the ways of preparing quantum-entangled states between atoms.Through the methods of resonant interaction or off-resonant interaction,EPR states,W states,GHZ states of atoms have been prepared.Thirdly, we study on the methods of implementing the controlled-not(CNOT) gates between two atoms.Finally,we discuss the two main types of dissipation-cavity photon decay and atomic spontaneous emission in cavity-QED setup. To avoid decoherence due to the dissipation, decoherence-free states(DFS) have been proposed to be used as qubits, which are exempt from decoherence in principle. Here the operation inside the DFS can be used to prepare atomic entangled states and implement a quantum logic gate.At last,we improve the original scheme,which therefore improves the feasibility of the gate operation.