The effects of amplitude damping in quantum noise channels on average fidelity of quantum teleportation are analyzed in Bloeh sphere representation for every stage of teleportation. When the quantum channels are varie...The effects of amplitude damping in quantum noise channels on average fidelity of quantum teleportation are analyzed in Bloeh sphere representation for every stage of teleportation. When the quantum channels are varied from maximally entangled states to non-maximally entangled states, it is found that the effects of noise channels on the fidelity are nearly equivalent to each other for strong quantum noise. The degree of damage on the fidelity of non-maximally entangled channels is smaller than that of maximally entangled channels. The average fidelity of values larger than 2/3 may be one representation indirectly showing how much the unavoidable quantum noise is.展开更多
Quantum teleportation via the entangled channel composed of a two-qubit Heisenberg XYZ model with Dzyaloshinski-Moriya （DM） interaction in the presence of intrinsic decoherence has been investigated. We find that th...Quantum teleportation via the entangled channel composed of a two-qubit Heisenberg XYZ model with Dzyaloshinski-Moriya （DM） interaction in the presence of intrinsic decoherence has been investigated. We find that the initial state of the channel plays an important role in the teleported state and the average fidelity of teleportation. When the initial channel is in the state ｜ψ1 （0）〉 = a｜00〉 ＋ b｜11〉, the average fidelity is equal to 1/3 constantly, which is independent of the DM interaction and the intrinsic decoherence effect. But when the channel is initially in the state ｜ψ2（0）〉 = a｜01〉 ＋ b｜10〉, the average fidelity is always larger than 2/3. Moreover, under a certain condition, the average fidelity can be enhanced by adjusting the DM interaction, and the intrinsic decoherence leads to a suppression of the fluctuation of the average fidelity.展开更多
Quantum walk is different from random walk in reversibility and interference. Observation of the reduced reversibility in a realistic quantum walk is of scientific interest in understanding the unique quantum behavior...Quantum walk is different from random walk in reversibility and interference. Observation of the reduced reversibility in a realistic quantum walk is of scientific interest in understanding the unique quantum behavior. We propose an idea to experimentally investigate the decoherence-induced irreversibility of quantum walks with trapped ions in phase space via the average fidelity decay. By introducing two controllable decoherence sources, i.e., the phase damping channel （i.e., dephasing） and the high temperature amplitude reservoir （i.e., dissipation）, in the intervals between the steps of quantum walk, we find that the high temperature amplitude reservoir shows more detrimental effects than the phase damping channel on quantum walks. Our study also shows that the average fidelity decay works better than the position variance for characterizing the transition from quantum walks to random walk. Experimental feasibility to monitor the irreversibility is justified using currently available techniques.展开更多
We first put forward a deterministic protocol to realize the remote preparation of arbitrary multi-qubit equatorial states via EPR pairs.A set of useful measurement basis is constructed which plays a key role.The rece...We first put forward a deterministic protocol to realize the remote preparation of arbitrary multi-qubit equatorial states via EPR pairs.A set of useful measurement basis is constructed which plays a key role.The receiver just needs to perform Pauli Z operations to recover the target state.Comparing with the previous protocols,the recovery operation is simplified and expressed by a general formula.As there are no universal protocols for high-dimensional systems,we further generalize to the case of multi-qudit equatorial states by means of Fourier transformation.It is worth mentioning that the proposed schemes can be extended to multi-party controlled remote state preparation.Moreover,we consider the effect of two-type decoherence noises.展开更多
Quantum teleportation is of significant meaning in quantum information. In this paper, we study the probabilistic teleportation of a two-qubit entangled state via a partially entangled Greenberger- Horne-Zeilinger （...Quantum teleportation is of significant meaning in quantum information. In this paper, we study the probabilistic teleportation of a two-qubit entangled state via a partially entangled Greenberger- Horne-Zeilinger （GHZ） state when the quantum channel information is only available to the sender. We formulate it as an unambiguous state discrimination problem and derive exact optimal positive-operator valued measure （POVM） operators for maximizing the probability of unambiguous discrimination. Only one three-qubit POVM for the sender, one two-qubit unitary operation for the receiver, and two chits for outcome notification are required in this scheme. The unitary operation is given in the form of a concise formula, and the fidelity is calculated. The scheme is further extended to more general case for transmitting a two-qubit entangled state prepared in arbitrary form. We show this scheme is flexible and applicable in the hop-by-hop teleportation situation.展开更多
基金The project supported by Special Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20050285002It is a pleasure to thank Profs. Yin-Sheng Ling and Jian-Xing Fang for their enlightening discussions on this topic.
文摘The effects of amplitude damping in quantum noise channels on average fidelity of quantum teleportation are analyzed in Bloeh sphere representation for every stage of teleportation. When the quantum channels are varied from maximally entangled states to non-maximally entangled states, it is found that the effects of noise channels on the fidelity are nearly equivalent to each other for strong quantum noise. The degree of damage on the fidelity of non-maximally entangled channels is smaller than that of maximally entangled channels. The average fidelity of values larger than 2/3 may be one representation indirectly showing how much the unavoidable quantum noise is.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60708003, 60578050 and 10434060)the National Basic Research Program of China (Grant No 2006CB921604)+1 种基金the Shanghai Science and Technology Committee (GrantNo 07JC14017)by the Director Fund of State Key Laboratory of Precision Spectroscopy
文摘Quantum teleportation via the entangled channel composed of a two-qubit Heisenberg XYZ model with Dzyaloshinski-Moriya （DM） interaction in the presence of intrinsic decoherence has been investigated. We find that the initial state of the channel plays an important role in the teleported state and the average fidelity of teleportation. When the initial channel is in the state ｜ψ1 （0）〉 = a｜00〉 ＋ b｜11〉, the average fidelity is equal to 1/3 constantly, which is independent of the DM interaction and the intrinsic decoherence effect. But when the channel is initially in the state ｜ψ2（0）〉 = a｜01〉 ＋ b｜10〉, the average fidelity is always larger than 2/3. Moreover, under a certain condition, the average fidelity can be enhanced by adjusting the DM interaction, and the intrinsic decoherence leads to a suppression of the fluctuation of the average fidelity.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974225, 10944005, and 11004029)
文摘Quantum walk is different from random walk in reversibility and interference. Observation of the reduced reversibility in a realistic quantum walk is of scientific interest in understanding the unique quantum behavior. We propose an idea to experimentally investigate the decoherence-induced irreversibility of quantum walks with trapped ions in phase space via the average fidelity decay. By introducing two controllable decoherence sources, i.e., the phase damping channel （i.e., dephasing） and the high temperature amplitude reservoir （i.e., dissipation）, in the intervals between the steps of quantum walk, we find that the high temperature amplitude reservoir shows more detrimental effects than the phase damping channel on quantum walks. Our study also shows that the average fidelity decay works better than the position variance for characterizing the transition from quantum walks to random walk. Experimental feasibility to monitor the irreversibility is justified using currently available techniques.
基金Supported by the National Natural Science Foundation of China(Grant Nos.62172341,62272208).
文摘We first put forward a deterministic protocol to realize the remote preparation of arbitrary multi-qubit equatorial states via EPR pairs.A set of useful measurement basis is constructed which plays a key role.The receiver just needs to perform Pauli Z operations to recover the target state.Comparing with the previous protocols,the recovery operation is simplified and expressed by a general formula.As there are no universal protocols for high-dimensional systems,we further generalize to the case of multi-qudit equatorial states by means of Fourier transformation.It is worth mentioning that the proposed schemes can be extended to multi-party controlled remote state preparation.Moreover,we consider the effect of two-type decoherence noises.
基金This work was supported by the National Natural Science Foundation of China （Grant No. 61601120） China Postdoctoral Science Foundation （Grant No. 2016M591742） and Jiangsu Planned Projects for Postdoctoral Research Funds （Grant No. 1601166C）.
文摘Quantum teleportation is of significant meaning in quantum information. In this paper, we study the probabilistic teleportation of a two-qubit entangled state via a partially entangled Greenberger- Horne-Zeilinger （GHZ） state when the quantum channel information is only available to the sender. We formulate it as an unambiguous state discrimination problem and derive exact optimal positive-operator valued measure （POVM） operators for maximizing the probability of unambiguous discrimination. Only one three-qubit POVM for the sender, one two-qubit unitary operation for the receiver, and two chits for outcome notification are required in this scheme. The unitary operation is given in the form of a concise formula, and the fidelity is calculated. The scheme is further extended to more general case for transmitting a two-qubit entangled state prepared in arbitrary form. We show this scheme is flexible and applicable in the hop-by-hop teleportation situation.
