Remote quantum-state discrimination is a critical step for the implementation of quantum communication network and distributed quantum computation. We present a protocol for remotely implementing the unambiguous discr...Remote quantum-state discrimination is a critical step for the implementation of quantum communication network and distributed quantum computation. We present a protocol for remotely implementing the unambiguous discrimination between nonorthogonal states using quantum entanglements, local operations, and classical communications. This protocol consists of a remote generalized measurement described by a positive operator valued measurement （POVM）. We explicitly construct the required remote POVM. The remote POVM can be realized by performing a nonlocal controlled-rotation operation on two spatially separated qubits, one is an ancillary qubit and the other is the qubit which is encoded by two nonorthogonal states to be distinguished, and a conventional local Von Neumann orthogonal measurement on the ancilla. The particular pair of states that can be remotely and unambiguously distinguished is specified by the state of the ancilla. The probability of successful discrimination is not optimal for all admissible pairs. However, for some subset it can be very close to an optimal value in an ordinary local POVM.展开更多
An efficient multipaxty quantum secret sharing scheme is proposed, in which the secret is a quantum state, and the dealer encodes the secret by performing the operations of quantum-controlled-not and Hadamard gate. Th...An efficient multipaxty quantum secret sharing scheme is proposed, in which the secret is a quantum state, and the dealer encodes the secret by performing the operations of quantum-controlled-not and Hadamard gate. The participants perform the single-particle measurements on their particles, and then can cooperate to recover the original quantum state. In our scheme, both the dealer and the participants do not need to perform the entanglement measurement. Compared with the existing schemes, our scheme is simpler and more efficient.展开更多
We propose a scheme to generate a superposition of motional coherent states with arbitrary coefficients on a line in phase space and implement a quantum controlled phase-gate for multiple trapped ions with a single st...We propose a scheme to generate a superposition of motional coherent states with arbitrary coefficients on a line in phase space and implement a quantum controlled phase-gate for multiple trapped ions with a single standing-wave laser pulse whose carrier frequency is tuned to the ions transition. In the scheme each ion does not need to be exactly positioned at the node of the standing wave, which is very important from viewpoint of experiment, Furthermore, our scheme may allow the generation of a superposition of coherent states with large mean phonon number for a large number of trapped ions in a fast way by choosing suitable laser intensity. We show that it can also be used to generate maximally entangled states of multiple trapped ions.展开更多
基金Project supported by the Natural Science Foundation of Guangdong Province,China(Grant Nos06029431and020127)the Natural Science Foundation of the Education Bureau of Guangdong Province,China(Grant No Z02069)
文摘Remote quantum-state discrimination is a critical step for the implementation of quantum communication network and distributed quantum computation. We present a protocol for remotely implementing the unambiguous discrimination between nonorthogonal states using quantum entanglements, local operations, and classical communications. This protocol consists of a remote generalized measurement described by a positive operator valued measurement （POVM）. We explicitly construct the required remote POVM. The remote POVM can be realized by performing a nonlocal controlled-rotation operation on two spatially separated qubits, one is an ancillary qubit and the other is the qubit which is encoded by two nonorthogonal states to be distinguished, and a conventional local Von Neumann orthogonal measurement on the ancilla. The particular pair of states that can be remotely and unambiguously distinguished is specified by the state of the ancilla. The probability of successful discrimination is not optimal for all admissible pairs. However, for some subset it can be very close to an optimal value in an ordinary local POVM.
文摘An efficient multipaxty quantum secret sharing scheme is proposed, in which the secret is a quantum state, and the dealer encodes the secret by performing the operations of quantum-controlled-not and Hadamard gate. The participants perform the single-particle measurements on their particles, and then can cooperate to recover the original quantum state. In our scheme, both the dealer and the participants do not need to perform the entanglement measurement. Compared with the existing schemes, our scheme is simpler and more efficient.
基金The project partially supported by National Fundamental Research Program of China under Grant No. 2005CB724508 and National Natural Science Foundation of China under Grant Nos. 60478029, 90503010, and 10575040 . We would like to thank Prof. Ying Wu for many enlightening discussions.
文摘We propose a scheme to generate a superposition of motional coherent states with arbitrary coefficients on a line in phase space and implement a quantum controlled phase-gate for multiple trapped ions with a single standing-wave laser pulse whose carrier frequency is tuned to the ions transition. In the scheme each ion does not need to be exactly positioned at the node of the standing wave, which is very important from viewpoint of experiment, Furthermore, our scheme may allow the generation of a superposition of coherent states with large mean phonon number for a large number of trapped ions in a fast way by choosing suitable laser intensity. We show that it can also be used to generate maximally entangled states of multiple trapped ions.
