International Journal of Modern Physics B

Discrete-time quantum walk evolve by a unitary operator which involves two operators a conditional shift in position space and a coin operator. This operator entangles the coin and position degrees of freedom of the walker. In this paper, we investigate the asymptotic behavior of the coin position entanglement (CPE) for an inhomogeneous quantum walk which determined by two orthogonal matrices in one-dimensional lattice. Free parameters of coin operator together provide many conditions under which a measurement perform on the coin state yield the value of entanglement on the resulting position quantum state. We study the problem analytically for all values that two free parameters of coin operator can take and the conditions under which entanglement becomes maximal are sought.

In this paper, glass sample was prepared by the conventional wet chemical method. A series of borate glass consists of lithium and potassium carbonate doped with 0.1mol% of NH₄ H₂PO₄ and copper oxides have been well prepared. The structural and the optical properties of the glass have been measured by means of their XRD, FTIR, PL and UV-VIS spectra. From the results, the current sample shows a nonlinear optical property by emitting two prominent peaks at 504 and 540 nm (green light emission) under the excitation of 630 nm. A significant enhancement on the PL spectra due to increment of phosphorus impurities dopant has also been observed. Some other physical parameters were also been measured and identified. The results of structural as well as the optical were then being estimated and discussed.

Molecular dynamics simulation is carried out for liquid SiO₂ at pressure ranged from zero to 30 GPa and by using BKS, Born–Mayer type and Morse–Stretch potentials. The constructed models reproduce well the experimental data in terms of mean coordination number, bond angle and pair radial distribution function. Furthermore, the density of all samples can be expressed by a linear function of fractions SiO_x. It is found that the topology of units SiO_x and linkages OSi_y is unchanged upon compression although the liquid undergoes substantial change in its network structure. Consequently, the partial bond angle distribution for SiO_x and OSi_y is identical for all samples constructed by the same potential. This result allows to establishing a simple expression between total bond angle distribution (BAD) and fraction of SiO_x and OSi_y. The simulation shows a good agreement between the calculation and simulation results for both total O–Si–O and Si–O–Si BADs. This supports a technique to estimate amount of units SiO_x and linkages OSi_y on base of total Si–O–Si and O–Si–O BADs measured experimentally.

Graphical approach provides a direct way to construct error correction codes. Motivated by its good properties, associating low-density parity-check (LDPC) codes, in this paper we present families of graphical quantum LDPC codes which contain no girth of four. Because of the fast algorithm of constructing for graphical codes, the proposed quantum codes have lower encoding complexity.

The thermodynamics of a free Bose gas with effective temperature scale and hard-sphere Bose gas with the scale are studied. arises as the temperature experienced by a single particle in a quantum gas with 2-body harmonic oscillator interaction V_osc, which at low temperatures is expected to simulate, almost correctly, the attractive part of the interatomic potential V_He between ⁴He atoms. The repulsive part of V_He is simulated by a hard-sphere (HS) potential. The thermodynamics of this system of HS bosons, with the temperature scale (HSET), and particle mass and density equal to those of ^4He, is investigated, first, by the Bogoliubov–Huang method and next by an improved version of this method, which describes He II in terms of dressed bosons and takes approximate account of those terms of the 2-body repulsion which are linear in the zero-momentum Bose operators a₀, (originally rejected by Bogoliubov). Theoretical heat capacity C_V(T) exhibits good agreement, below 1.9 K, with the experimental heat capacity graph observed in ⁴He at saturated vapour pressure. The phase transition to the He II phase, occurs in the HSET at T_λ = 2.17 K, and is accompanied, in the modified HSET version, by a singularity of C_V(T). The fraction of atoms in the momentum condensate at 0 K equals 8.86% and agrees with other theoretical estimates for He II. The fraction of normal fluid falls to 8.37% at 0 K which exceeds the value 0% found in He II.

Projective synchronization investigates the synchronization of systems evolve in same orientation, however, in practice, the situation of same orientation is only minority, and the majority is different orientation. This paper investigates the latter, proposes the concept of rotating synchronization, and verifies its necessity and feasibility via theoretical analysis and numerical simulations. Three conclusions were elicited: first, in three-dimensional space, two arbitrary nonlinear chaotic systems who evolve in different orientation can realize synchronization at end; second, projective synchronization is a special case of rotating synchronization, so, the application fields of rotating synchronization is more broadly than that of the former; third, the overall evolving information can be reflected by single state variable's evolving, it has self-similarity, this is the same as the basic idea of phase space reconstruction method, it indicates that we got the same result from different approach, so, our method and the phase space reconstruction method are verified each other.

We present a multiparty quantum secret sharing scheme of classical information with Bell states and decoy states. This scheme can save a lot of photons because eavesdropping checks are performed only twice; in addition, it has the advantage of high intrinsic efficiency for qubits because every Bell states can generate two bits of classical secret information; moreover, only the dealer and one of the agents are required to store photons; most important of all, this scheme can resist all the attacks that have been proposed.