Is computation reversible?

Recent studies have suggested that computation is essentially reversible, provided no information is lost. This is a consequence of Landauer’s principle which only requires energy expenditure and entropy increase for information deletion. In this paper we propose to treat information as being intrinsic to points of non-analyticity, so that the movement of information is always associated with the dissipation of heat. This allows us to construct a theory consistent with causality, and the second law of thermodynamics. Since computation requires the movement of information bits through finite volume gates, energy is dissipated even when information is not destroyed, thus indicating that computation is fundamentally non-reversible.     

Restoration of a Poisson distributed image using a principle of extreme physical information

Suppose that an object which reflects or emits light is captured by a sensor. The image data are distorted in various ways. The aim is to restore the object. For this purpose, a new restoration method is devised. It uses the Fisher-information based principle of extreme physical information (EPI). This solves a variational problem I − J = extremum, expressing a flow of information J → I from source to output in the restoration problem. Here, the source of information is the Poissonian image data, and J is modeled as its Hartley information level. Also, I is the Fisher information in the output restored object. The approach dates from the 1980s. It has been already shown that many fundamental physical laws may be derived using EPI. In this paper, the EPI approach is applied to the restoration problem, wherein it regards the unknown restoration as another fundamental law. It models the source information J as obeying Poisson statistics, and assumes additional image distortions that are due to additive Gaussian noise and quantization of the image data. It is found that the quantization level determines the degree of smoothness (or sharpness) of the restored signal. An optimal level of image quantization can be accomplished by adjusting its cross entropy. Finally, the restoration method by EPI is validated by numerical simulations of the image forming and restoring system.     

Relativistic non-Hamiltonian mechanics

Relativistic particle subjected to a general four-force is considered as a nonholonomic system. The nonholonomic constraint in four-dimensional space-time represents the relativistic invariance by the equation for four-velocity u_μu^μ + c² = 0, where c is the speed of light in vacuum. In the general case, four-forces are non-potential, and the relativistic particle is a non-Hamiltonian system in four-dimensional pseudo-Euclidean space-time. We consider non-Hamiltonian and dissipative systems in relativistic mechanics. Covariant forms of the principle of stationary action and the Hamilton’s principle for relativistic mechanics of non-Hamiltonian systems are discussed. The equivalence of these principles is considered for relativistic particles subjected to potential and non-potential forces. We note that the equations of motion which follow from the Hamilton’s principle are not equivalent to the equations which follow from the variational principle of stationary action. The Hamilton’s principle and the principle of stationary action are not compatible in the case of systems with nonholonomic constraint and the potential forces. The principle of stationary action for relativistic particle subjected to non-potential forces can be used if the Helmholtz conditions are satisfied. The Hamilton’s principle and the principle of stationary action are equivalent only for a special class of relativistic non-Hamiltonian systems.     

Temperature dependent coercivity and magnetization of nickel ferrite nanoparticles

Magnetic nanoparticles of nickel ferrite (size: 24±4 nm) have been synthesized by chemical coprecipitation method using stable ferric and nickel salts. Coercivity of nanoparticles has been found to increase with decrease in temperature of the samples. It has been observed that the coercivity follows a simple model of thermal activation of particle’s moment over the anisotropy barrier in the temperature range (10-300 K), in accordance with Kneller’s law for ferromagnetic materials. Saturation magnetization follows the modified Bloch’s law in the temperature range from 300 to 50 K. However, below 50 K, an abrupt increase in magnetization of nanoparticles was observed. This increase in magnetization at lower temperatures was explained with reference to the presence of freezed surface-spins and some paramagnetic impurities at the shell of nanoparticles that are activated at lower temperatures in core-shell nickel ferrite nanoparticles.     

New relations for coefficients of fractional parentage—The Redmond recursion formula with seniority

We find a relationship between coefficients of fractional parentage (cfp) obtained on the one hand from the principal-parent method and on the other hand from a seniority classification. We apply this to the Redmond recursion formula which relates n → n + 1 cfp’s to n − 1 → n cfp’s where the principal-parent classification is used. We transform this to the seniority scheme. Our formula differs from the Redmond formula inasmuch as we have a sum over the possible seniorities for the n → n + 1 cfp’s, whereas Redmond has only one term. We show that there are useful applications of both the principal-parent and the seniority classification.     

Continuous-wave Ho:GdVO4 laser pumped by Tm-doped fiber laser with a fiber Bragg grating at room temperature

We reported the Ho:GdVO₄ laser pumped by Tm-doped laser with a fiber Bragg grating. 2.03 W continuous-wave Ho:GdVO₄ laser output power is obtained under 10.5 W incident pump power, with the optical-to-optical conversion efficiency and slope efficiency of 19.3% and 32.3%, respectively, at 7 °C. We can see that, the lower the temperature is, the better the laser output character is. The beam quality factor is M² ∼ 1.29 measured by the traveling knife-edge method.     

Dielectric relaxation and magnetic field dependent alternating current conductivity of nanocrystalline cadmium-zinc ferrite below room temperature

The dielectric permittivity of nanocrystalline cadmium-zinc ferrite prepared by the ball milling method has been investigated within a temperature range 77≤T≤300 K in presence of a magnetic field up to 1 T and in the frequency range 20 Hz-1 MHz. The dielectric permittivity follows the power law ε^/(f)∝Tⁿ where the temperature exponent ‘n’ is found to be frequency dependent. The dielectric properties of the samples have been analyzed in terms of electric modulus vector. The dielectric relaxation has been explained by interfacial polarization. The variation of the relaxation time with temperature indicates the presence of two different activation energies. The ac magnetoconductivity is positive for the milled sample and becomes negative for the unmilled sample. This behavior can be explained in terms of grain and grain boundary contribution to impedance of the samples.     

Cryptanalysis and Improvement of a Multi-User Quantum Communication Network Using χ-Type Entangled States

The security of a multi-user quantum communication network protocol using χ-type entangled states (Chang et al., J. Korean Phys. Soc. 61:1–5, 2012) is analyzed. We find that, by using one χ-type state in this protocol, two participants can only share 2 bits of information, not 4 bits as the authors stated. In addition, we give a special attack strategy by which an eavesdropper can elicit half of the secret information without being detected. Finally, we improve the protocol to be secure against all the present attacks.     

Microstructure and nanohardness of the diluted magnetic semiconducting Cd1−xMnxS nano-crystalline films

Cd_1−xMn_xS nano-crystalline films (0 ≤ x ≤ 0.5) were formed on glass substrates by thermal evaporation technique at room temperature (300 K). AFM studies showed that all the films were in nano-crystalline form with the grain size varying in the range between 36 and 58 nm and exhibited hexagonal structure of the host material. The lattice parameters varied linearly with composition, following Vegard's law in the entire composition range. The nanohardness and Young's modulus decreased sharply with ‘Mn’ content upto x = 0.3 and increased with high Mn content.     

Spectral switching-based fan-out architecture and information processing in free-space

In this paper, we elaborate different type of spectral switching techniques and spectral switching-based information processing (SSBIP) schemes. On the basis of theoretical, experimental and empirical studies carried out so far on spectral switching, we demonstrate novel type of interference-induced 1 × N (1 input N outputs) and 1 × N × M (1 input N × M outputs) spectral switching-based fan-out architectures for information transmission in free-space. In addition, a comprehensive analysis is presented to explore the feasibility of SSBIP scheme in contrast to the recent technological advancements. The spectral switching-based techniques are contrived ideas but might find potential applications in optical computing, state-of-the-art technique like SIMO (single-input multiple-output), free-space optical (FSO) interconnects and polychromatic light-based FSO communications.     

Diode-pumped Yb:KYW thin-disk laser operation with wavelength tuning to small quantum defects

We present continuous wave laser operation of a diode-pumped Yb:KY(WO₄)₂ thin-disk laser with 10.7 W output power, M² = 1.3 and an optical efficiency of 49% at room temperature. Wavelength tuning in a range of 64 nm and lasing with a quantum defect of 0.6% is demonstrated.     

Constructions and properties of k out of n scalable secret image sharing

Recently, Wang et al. introduced a novel (2, n) scalable secret image sharing (SSIS) scheme, which can gradually reconstruct a secret image in a scalable manner in which the amount of secret information is proportional to the number of participants. However, Wang et al.’s scheme is only a simple 2-out-of-n case. In this paper, we consider (k, n)-SSIS schemes where a qualified set of participants consists of any k participants. We provide two approaches for a general construction for any k, 2 ? k ? n. For the special case k = 2, Approach 1 has the lesser shadow size than Wang et al.’s (2, n)-SSIS scheme, and Approach 2 is reduced to Wang et al.’s (2, n)-SSIS scheme. Although the authors claim that Wang et al.’s (2, n)-SSIS scheme can be easily extended to a general (k, n)-SISS scheme, actually the extension is not that easy as they claimed. For the completeness of describing the constructions and properties of a general (k, n)-SSIS scheme, both approaches are introduced in this paper.     

Efficient tunable Yb:YAG ceramic laser

A high-power efficient ceramic Yb:YAG laser was demonstrated at a room temperature of 20 °C with an Yb concentration of 9.8 at.%, a gain medium of 1 mm, a pumping power of 13.8 W, an output coupler of T = 10%, and a cavity length of 20 mm. A 6.8 W cw output power was obtained with a slope efficiency of 72%. The ceramic Yb:YAG laser exhibited a continuous tunability in the spectral range of 63.5 nm from 1020.1 to 1083.6 nm for T = 1% at a maximum output power of 1.6 W. To the best of our knowledge, this is the first study of the tunability of ceramic Yb:YAG lasers, except crystal Yb:YAG studies.     

A hybrid numerical method for interfacial fluid flow with soluble surfactant

We address a significant difficulty in the numerical computation of fluid interfaces with soluble surfactant that occurs in the physically representative limit of large bulk Peclet number Pe. At the high values of Pe in typical fluid-surfactant systems, there is a transition layer near the interface in which the surfactant concentration varies rapidly, and large gradients at the interface must be resolved accurately to evaluate the exchange of surfactant between the interface and bulk flow. We use the slenderness of the layer to develop a fast and accurate ‘hybrid’ numerical method that incorporates a separate, singular perturbation analysis of the dynamics in the transition layer into a full numerical solution of the interfacial free boundary problem. The accuracy and efficiency of the method is assessed by comparison with a more ‘traditional’ numerical approach that uses finite differences on a curvilinear coordinate system exterior to the bubble, without the separate transition layer reduction. The traditional method implemented here features a novel fast calculation of fluid velocity off the interface.     

Effect of doping concentration on the structural and optical properties of pure and tin doped zinc oxide thin films by nebulizer spray pyrolysis (NSP) technique

Pure and tin doped zinc oxide (Sn:ZnO) thin films were prepared for the first time by NSP technique using aqueous solutions of zinc acetate dehydrate, tin (IV) chloride fendahydrate and methanol. X-ray diffraction patterns confirm that the films are polycrystalline in nature exhibiting hexagonal wurtzite type, with (0 0 2) as preferred orientation. The structural parameters such as lattice constant (‘a’ and ‘c’), crystallite size, dislocation density, micro strain, stress and texture coefficient were calculated from X-ray diffraction studies. Surface morphology was found to be modified with increasing Sn doping concentration. The ZnO films have high transmittance 85% in the visible region, and the transmittance is found to be decreased with the increase of Sn doping concentration. The corresponding optical band gap decreases from 3.25 to 3.08 eV. Room temperature photoluminescence reveals the sharp emission of strong UV peak at 400 nm (3.10 eV) and a strong sharp green luminescence at 528 nm (2.34 eV) in the Sn doped ZnO films. The electrical resistivity is found to be 10⁶ Ω-cm at higher temperature and 10⁵ Ω-cm at lower temperature.     

Dielectric and AC conductivity behavior of BaBi2Nb2O9 ceramics

The complex dielectric and AC conductivity response of BaBi₂Nb₂O₉ relaxor ferroelectric ceramics were studied as a function of frequency (100 Hz-10 MHz) at various temperatures. The observed dielectric behavior was characterized by two types of relaxation processes which were described by the ‘universal relaxation law’. The frequency dependence of conductivity which showed a classical relaxor behavior followed the Jonscher's universal law σ(ω)=σ₀+Aωⁿ. The exponent n exhibited a minimum in the vicinity of temperatures of dielectric anomaly while the pre-factor A showed a maximum. The temperature dependence of n followed the Vogel-Fulcher relation with activation energy of about 0.14 eV.     

Effect of Mn-doping on the electrical properties of Cu2GeSe3

In this work we report the temperature dependence of the resistivity ρ of p-Cu₂GeSe₃ and manganese-doped p-Cu₂GeSe₃ at low temperature. It was found that for a intrinsic sample ρ obeys the Shklovskii-Efros-type variable-range hopping resistivity law in the temperature range from 4 to 63 K. This behaviour is governed by generation of a Coulomb gap Δ=78 meV in the density of localized states. We find a low activation term T₀=0.24 K, which is an indication of a large localization length ξ. For Mn-doped sample a metal-insulator transition (MIT) is observed at T=65 K. On the basis of the Mott criterion for metal-insulator transition, the critical carrier density n_c is determined. From the analysis of resistivity data it is concluded that Mn acts as acceptor impurity.     

Novel procedure for the simultaneous determination of the Debye length and electro-optic coefficient for an optically active photorefractive Bi12SiO20 crystal

We present a novel procedure based on an improved physical model and a versatile numerical fitting technique, to simultaneously determinate the Debye screening length and electro-optic coefficient using a thick sample of an optically active photorefractive crystal Bi₁₂SiO₂₀ (BSO). For the computation, experimental data of gain vs. grating spacing were obtained by a two-beam coupling arrangement. Unlike former calculation models, in our work, the general expression for the diffraction efficiency in the presence of self-diffraction is considered, and the influence of the optical activity in the coupling parameters is had into account for the calculation of the gain values. The fitting of the experimental data to the predicted theoretical behavior by our model is achieved by finding the closest theoretical curve to a set of data sampled from a spline-smoothed curve of the experimental data. Both, the Debye screening length l_s and the electro-optic coefficient r₄₁ are used as fitting parameters by searching in a rather wide range for each one of the parameters, so that, the estimation of their values is obtained in a more reliable and direct way from the same experiment. The calculations are performed in diffusion regimen and the procedure leads to l_s = 0.22 μm and r₄₁ = 4.5 × 10 ^− 12m/V. Because the optical activity can alter the maximum gain and self-diffraction effects influence the energy exchange, the procedure reveals to be physically appropriated for the simultaneous determination of these physical parameters when thick photorefractive crystals with high optical activity are considered.     

Intracavity frequency doubling of an active Q-switched Nd:YAG laser with 2.25 W output power at 473 nm

An active Q-switched diode-end-pumped Nd:YAG laser is reported with 2.9 W output power on the ⁴F_3/2 → ⁴I_9/2 transitions at a pump power of 24 W. With intracavity frequency doubling using a 20-mm-long LBO, a maximum blue output power of 2.25 W is achieved at a repetition rate of 23 kHz. The conversion efficiency from the corresponding Q-switched fundamental output to blue output is 96%. The peak power of the Q-switched blue pulse is up to 610 W with 160 ns pulse width. The fluctuation of the blue output power is less than 4.0% at the maximum output power.