Research About The Logic Network Of Quantum Cloning And Corresponding Physical Realization

Quantum no-cloning theorem prohibits an arbitrary quantum state from being copied perfectly because of the linearity of quantum mechanics. So a lot of attention has been paid to approximate cloning. In this dissertation, we propose several schemes for implementing quantum cloning and telecloning based on quantum logic network and cavity QED. The main results of research of this dissertation is as follows(1) We propose a scheme to implement optimal universal, phase-covariant, eco-nomical phase-covariant telecloning of a bipartite entangled state based on quantum logic network. The quantum logic circuits are constructed for quantum cloning. Sev-eral kinds of quantum channels can be prepared by choosing different parameter in the same network. Due to the network is composed of one and two-qubit operations, it can be easily implemented in experiment.(2) A scheme for implementing 1→M economical phase-covariant quantum cloning and telecloning based on cavity QED is proposed. The 1→M economical phase-covariant quantum cloning can be implemented by using N three-level atoms nonresonantly interacting with a cavity assisted by a classical laser field. The two kinds of telecloning channel, maximal-W state and partial-W state, can be prepared by the same evolution process as local cloning and some local operations. If the range of input state is partial known, we obtain the higher fidelity and probability by choosing one of the channels. Hence the scheme is more efficient for preparing the quantum telecloning channel and improving the fidelity.(3) A scheme to implement 1→M economical phase-covariant quantum anti-cloning is proposed. By using the symmetric and asymmetric interactions between N atoms and the cavity, N-particles Greenberger-Horne-Zeilinger (GHZ) and W states are prepared, respectively. Furthermore, a scheme of 1→M anti-cloning is also proposed though preparing the W state by one step. The decoherence from atomic spontaneous emission is negligible due to the excited state of the atom is adiabatically eliminated under large detuning. The scheme is insensitive to the cavity decay due to the cavity is only virtually excited. Hence the scheme is feasible based on the current technology.The above results provide the reliable theoretical foundation for the effective extraction of quantum information, and it has the theoretical guideline and impor-tant reference value for research of quantum cloning experiment.