We propose a scheme for realizing controlled 1→2 telecloning and 1 →1 teleflipping for one-qubit pure states via a quantum network including N agents. The quantum operations used in the information-transmission proc...We propose a scheme for realizing controlled 1→2 telecloning and 1 →1 teleflipping for one-qubit pure states via a quantum network including N agents. The quantum operations used in the information-transmission process are just only one Bell-state measurement, and a series of single-qubit operation. It is shown that the fidelities of the controlled telecloning and teleflipping are independent of the initial states and reach their optimal values of 5/6 and 2/3 respectively on the condition that all the agents collaborate. If any one agent does not cooperate, the fidelities become state-dependent and are always smaller than the corresponding optimal values. The average fidelities are equal to the balanced value 1/2, which implies that on average the state ineepted by any one of the receivers is a fuUy mixed state. Thus no information leaks out to any dishonest receivers. The security of telecloning and teleflipping have been increased greatly.展开更多
We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum t...We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum time required to steer the system from an initial state to a specified final state.As applications the minimal time to implement Controlled-NOT gate,SWAP gate and Controlled-U gate is calculated in detail.The experimental realizations of these quantum gates are explicitly presented.展开更多
基金supported by the Natural Science Foundation of Hunan Province under Grant No. 06JJ50118the Key Project of Chinese Ministry of Education under Grant No. 206103+1 种基金the National Natural Science Foundation of China under Grant No. 10775048the National Fundamental Research Program of China under Grant No. 2007CB925204
文摘We propose a scheme for realizing controlled 1→2 telecloning and 1 →1 teleflipping for one-qubit pure states via a quantum network including N agents. The quantum operations used in the information-transmission process are just only one Bell-state measurement, and a series of single-qubit operation. It is shown that the fidelities of the controlled telecloning and teleflipping are independent of the initial states and reach their optimal values of 5/6 and 2/3 respectively on the condition that all the agents collaborate. If any one agent does not cooperate, the fidelities become state-dependent and are always smaller than the corresponding optimal values. The average fidelities are equal to the balanced value 1/2, which implies that on average the state ineepted by any one of the receivers is a fuUy mixed state. Thus no information leaks out to any dishonest receivers. The security of telecloning and teleflipping have been increased greatly.
基金supported by the National Natural Science Foundation of China(Grant No.11275131)the National Research Foundation for the Doctoral Program of Higher Education of China
文摘We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum time required to steer the system from an initial state to a specified final state.As applications the minimal time to implement Controlled-NOT gate,SWAP gate and Controlled-U gate is calculated in detail.The experimental realizations of these quantum gates are explicitly presented.
