Chinese Physics B

Li-Li, Xia; Jian-Le, Cai; Yuan-Cheng, Li

doi: 10.1088/1674-1056/18/8/011pmid: N/A

This paper studies the conformal invariance and conserved quantities of general holonomic systems in phase space. The definition and the determining equation of conformal invariance for general holonomic systems in phase space are provided. The conformal factor expression is deduced from conformal invariance and Lie symmetry. The relationship between the conformal invariance and the Lie symmetry is discussed, and the necessary and sufficient condition that the conformal invariance would be the Lie symmetry of the system under the infinitesimal single-parameter transformation group is deduced. The conserved quantities of the system are given. An example is given to illustrate the application of the result.

Wen-Hua, Huang

doi: 10.1088/1674-1056/18/8/012pmid: N/A

A general solution, including three arbitrary functions, is obtained for a (2+1)-dimensional modified dispersive water-wave (MDWW) equation by means of the WTC truncation method. Introducing proper multiple valued functions and Jacobi elliptic functions in the seed solution, special types of periodic folded waves are derived. In the long wave limit these periodic folded wave patterns may degenerate into single localized folded solitary wave excitations. The interactions of the periodic folded waves and the degenerated single folded solitary waves are investigated graphically and found to be completely elastic.

Xi-Jun, Deng; Zi-Zong, Yan; Li-Bo, Han

doi: 10.1088/1674-1056/18/8/013pmid: N/A

In this paper, the travelling wave solutions for the generalized BurgersHuxley equation with nonlinear terms of any order are studied. By using the first integral method, which is based on the divisor theorem, some exact explicit travelling solitary wave solutions for the above equation are obtained. As a result, some minor errors and some known results in the previousl literature are clarified and improved.

Jian-Bing, Li; Xue-Song, Wang; Tao, Wang

doi: 10.1088/1674-1056/18/8/014pmid: N/A

This paper intends to identify the validity of the orn approximation by a new universal criterion, which is ultimately reduced to the calculation of an operator norm. With the purpose of enabling the criterion to be applicable to general scattering problems, a method is proposed to estimate the norm of the operator concerned. Compared with the conventional criterion, this method excels in its ability to acquire a quantificational upper bound of the relative error by Born approximation as well as to extend its valid frequency to a wider range. Two canonical scattering examples are given as evidence for the validity of the criterion.

Xiao-Hong, Hu; Wei, Zhao; Yong-Kang, Gong; Lei-Ran, Wang; Ke-Qing, Lu; Xue-Ming, Liu

doi: 10.1088/1674-1056/18/8/015pmid: N/A

Exact solutions of Maxwell's equations describing the lightwave through 3-layer-structured cylindrical waveguide are obtained and the mode field diameter and nonlinear coefficient of air-core nanowires (ACNWs) are numerically calculated. The simulation results show that ACNWs offer some unique optical properties, such as tight field confining ability and extremely high nonlinearity. At a certain wavelength and air core radius, we optimize the waveguide design to maximize the nonlinear coefficient and minimize the mode field diameter. Our results show that the ACNWs may be powerful potential tools for novel micro-photonic devices in the near future.

Tian-Yin, Wang; Qiao-Yan, Wen; Fu-Chen, Zhu

doi: 10.1088/1674-1056/18/8/016pmid: N/A

This paper proposes a scheme for secure authentication of classical messages with single photons and a hashed function. The security analysis of this scheme is also given, which shows that anyone cannot forge valid message authentication codes (MACs). In addition, the lengths of the authentication key and the MACs are invariable and shorter, in comparison with those presented authentication schemes. Moreover, quantum data storage and entanglement are not required in this scheme. Therefore, this scheme is more efficient and economical.

Fei, Jia; Shuang-Yuan, Xie; Ya-Ping, Yang

doi: 10.1088/1674-1056/18/8/017pmid: N/A

The interactions between a two-level atom and a field via two-photon transition without rotating wave approximation have been investigated. We emphasize the dynamic behaviors of the atomic population inversion, the field squeezing, and the atomic dipole squeezing numerically when the field frequency varies with time in the forms of sine and rectangle. Some interesting phenomena are discovered and discussed. The good periodic character of the atomic population inversion in the standard two-photon JaynesCummings model is weakened by the influence of the sine field frequency modulation. The rectangular field frequency modulation can change the correlation among different oscillations suddenly and induce new collapse-revival processes of the atomic population inversion. The field squeezing increases at the beginning of time, but then decreases and loses as the time increases after it reaches the maximum due to the sine modulation. The effects of the rectangular modulation on the field squeezing depend mostly on the appearance time of the modulation. The atomic dipole squeezing is weakened under the influence of the sine or rectangular modulation. Our results indicate that it is possible to perform the dynamic controlling of the system properties by changing the parameters of the system with time. This implies that one can dynamically control a quantum information process by choosing the system modulation properly.

Li-Jun, Xie; Deng-Yu, Zhang; Shi-Qing, Tang; Xiao-Gui, Zhan; Feng, Gao

doi: 10.1088/1674-1056/18/8/018pmid: N/A

This paper investigates the thermal pairwise entanglement of a three-qubit Heisenberg XXZ chain in the presence of the DzyaloshinskiMoriya (DM) anisotropic antisymmetric interaction and quantum teleportation when using the Heisenberg chain as a channel. The entanglement dependences on the DM interaction and temperature are given in detail. It obtains the relation between the concurrence and average fidelity, and shows that the same concurrence can lead different average fidelities. Moreover, it finds the thermally entangled states which do not violate the Bell inequalities, and can still be used for quantum teleportation.

Qiang, Zheng; Xiao-Ping, Zhang; Qi-Jun, Zhi; Zhong-Zhou, Ren

doi: 10.1088/1674-1056/18/8/019pmid: N/A

This paper investigates the entanglement dynamics of the system, composed of two qubits A and B with Heisenberg XX spin interactation. There is a third controller qubit C, which only has DzyaloshinskiiMoriya (DM) spin-orbit interaction with the qubit B. It is found that depending on the initial state of the controller qubit C and DM interaction, the entanglement of the system displays amplification and sudden birth effects. These effects indicate that one can control the entanglement of the system, which may be helpful for quantum information processing.

Yang, Han; Chun-Wang, Wu; Wei, Wu; Ping-Xing, Chen; Cheng-Zu, Li

doi: 10.1088/1674-1056/18/8/020pmid: N/A

To implement generalized quantum measurement (GQM) one has to extend the original Hilbert space. Generally speaking, the additional dimensions of the ancilla space increase as the number of the operators of the GQM n increases. This paper presents a scheme for deterministically implementing all possible n-operator GQMs on a single atomic qubit by using only one 2-dimensional ancillary atomic qubit repeatedly, which remarkably reduces the complexity of the realistic physical system. Here the qubit is encoded in the internal states of an atom trapped in an optical cavity and single-photon pulses are employed to provide the interaction between qubits. It shows that the scheme can be performed remotely, and thus it is suitable for implementing GQM in a quantum network. What is more, the number of the total ancilla dimensions in our scheme achieves the theoretic low bound.