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Secure Communication Based on Quantum Key

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Communications in Theoretical Physics 2008年第3期49卷 635-638页

作者： song Jie XIA Yan song he-shan School of Physic and Optoelectronic Technology Dalian University of Technology Dalian 116024 China

We introduce a protocol for QKD based on reusable entangled states. In this protocol, the EPR pairs act as a quantum key to encode and decode information particles. And only an information particle travels between the legitimated users. This improves the security and efficiency of communication. In addition, we show that its extension to a new QSS protocol is also secure and efficient.

关键词： secure communication EPR pairs unitary operation

Maximally Generalized Yang-Mills Model and Dynamical Breaking of Gauge Symmetry

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Communications in Theoretical Physics 2006年第2期45卷 297-300页

作者： WANG Dian-Fu song he-shan Department of Physics Dalian Maritime University Dalian 116024 China Department of Physics Dalian University of Technology Dalian 116024 China

A maximally generalized Yang-Mills model, which contains, besides the vector part Vμ, also an axial-vector part Aμ, a scalar part S, a pseudoscalar part P, and a tensor part Tμv, is constructed and the dynamical breaking of gauge symmetry in the model is also discussed. It is shown, in terms of the Nambu Jona-Lasinio mechanism, that the gauge symmetry breaking can be realized dynamically in the maximally generalized Yang-Mills model. The combination of the maximally generalized Yang-Mills model and the NJL mechanism provides a way to overcome the difficulties related to the Higgs field and the Higgs mechanism in the usual spontaneous symmetry breaking theory.

关键词： Yang-Millstheory dynamical-symmetry breaking

Quantum Key Distribution Using Four-Qubit W State

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Communications in Theoretical Physics 2006年第1X期46卷 65-68页

作者： CAO Hai-Jing song he-shan Department of Physics Dalian University of Technology Dalian 116024 China

A new theoretical quantum key distribution scheme based on entanglement swapping is proposed, where four-qubit symmetric W state functions as quantum channel. It is shown that two legitimate users can secretly share a... 详细信息

关键词： quantum key distribution W state Bell-state measurement security

Controlled Secure Quantum Dialogue Using a Pure Entangled GHZ States

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Communications in Theoretical Physics 2007年第5X期48卷 841-846页

作者： XIA Yan song Jie NIE Jing song he-shan School of Physics and Optoelectronic Technology Dalian University of Technology Dalian 116024 China

We present a controlled secure quantum dialogue protocol using a non-maximally （pure） entangled Greenberger-Horne-Zeibinger （GHZ） states at first, and then discuss the requirements for a real quantum dialogue. We show that the authorized two users can exchange their secret messages after purifying the non-maximally entangled GHZ states quantum channel unconditionally securely and simultaneously under the control of a third party.

关键词： controlled secure quantum dialogue eavesdropper non-maximally entangled GHZ state

A New Quantum Communication Scheme by Using Bell States

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Communications in Theoretical Physics 2006年第2期45卷 271-274页

作者： CAO Hai-Jing CheN Jing song he-shan Department of Physics Dalian University of Technology Dalian 116024 China

A new quantum communication scheme based on entanglement swapping is presented. Simplified calculation symbols are adopted to realize the process. Quantum key distribution and quantum secure direct communication can be simultaneously accomplished in the scheme. Two legitimate communicators can secretly share four certain key bits and four random key bits via three EPR pairs （quantum channels）.

关键词： quantum key distribution quantum secure direct communication Bell-state measurements security

Quantum Teleportation Through a Two-Qubit heisenberg XXZ Chain

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Communications in Theoretical Physics 2008年第6期49卷 1435-1438页

作者： GUO Jin-Liang NIE Jing song he-shan School of Physics and Optoelectronic Technology Dalian University of Technology Dalian 116024 China

We consider a two-qubit heisenberg XXZ chain as a resource for quantum teleportation via the standard teleportation protocol To. The effects of anisotropic on teleportation fidelity and entanglement are studied in detail. We find anisotropic not only improves the criticM temperature Tc and criticM magnetic field Bc, beyond which quantum teleportation is inferior to classicM communication protocol, but also enhances the fidelity for fixed magnetic field B and temperature T. For entanglement teleportation, the effects of magnetic field on average fidelity and output entanglement are studied.

关键词： thermal entanglement negativity two-qubit heisenberg XXZ chain

Decoherence of a Quantum Nonlinear Oscillator Under a Non-zero Temperature Thermal Bath

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Communications in Theoretical Physics 2006年第3期45卷 542-546页

作者： HAN Li-Ping ZHOU Ling song he-shan Department of Physics Dalian University of Technology Dalian 116023 China

The characteristic time τD for decoherence process of a quantum nonlinear oscillator system under a nonzero temperature thermal bath is studied by expanding the linear entropy. By numerical analysis, it is shown that at a non-zero temperature, the quantum coherence decays much faster than at zero temperature. Moreover, the non-zero temperature thermal bath will bring a crucial suppression to the quantum effects of the observables, which causes these quantum effects to become unable to persist up to the Ehrenfest time but is insufticient to destroy the quantum-classical transition.

关键词： quantum nonlinear oscillator linear entropy decoherence timscale

Elementary Quantum Gates Based on Intrinsic Interaction Hamiltonian

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Communications in Theoretical Physics 2006年第1X期46卷 69-72页

作者： CheN Jing YU Chang-Shui song he-shan Department of Physics Dalian University of Technology Dalian 116023 China

A kind of new operators, the generalized pseudo-spin operators are introduced and a universad intrinsic Hamiltonian of two-qubit interaction is studied in terms of the generalized pseudo-spin operators. A fundamental quantum gate U（θ） is constructed based on the universal Hamiltonian and shown that the roles of the new quantum gate U （θ） is equivalent, functionally, to the joint operation of Hadamard and C-Not gates.

关键词： quantum gate intrinsic Hamiltonian

Teleportations of Mixed States and Multipartite Quantum States

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Communications in Theoretical Physics 2007年第6期47卷 1041-1044页

作者： YU Chang-Shui WANG Ya-Hong song he-shan Department of Physic＇s Dalian University of Technology Dalian 116024 China School of Information Science and Engineering Dalian Institute of Light Industry Dalian 116034 China

In this paper, we propose a protocol to deterministically teleport an unknown mixed state of qubit by utilizing a maximally bipartite entangled state of qubits as quantum channel. Ira non-maximally entangled bipartite pure state is employed as quantum channel, the unknown mixed quantum state of qubit can be teleported with 1 -√ 1- C^2 probability, where C is the concurrence of the quantum channel. The protocol can also be generalized to teleport a mixed state of qudit or a multipartite mixed state. More important purpose is that, on the basis of the protocol, the teleportation of an arbitrary multipartite （pure or mixed） quantum state can be decomposed into the teleportation of each subsystem by employing separate entangled states as quantum channels. In the case of deterministic teleportation, Bob only needs to perform unitary transformations on his single particles in order to recover the initial teleported multipartite quantum state.

关键词： teleportation mixed state multipartite quantum state