A Modified Szilard Engine: Measurement, Information, and Maxwell's Demon

Using an isolated measurement process, we calculate the effect measurement has on entropy for the multi-cylinder Szilard engine. We find that the system of cylinders possesses an entropy associated with cylinder total energy states, and that it records information transferred at measurement. Contrary to other's results, we find that the apparatus loses entropy due to measurement. The Second Law of Thermodynamics may be preserved if Maxwell's demon gains entropy moving the engine partition.     

Level shift operators for open quantum systems

Level shift operators describe the second-order displacement of eigenvalues under perturbation. They play a central role in resonance theory and ergodic theory of open quantum systems at positive temperatures. We exhibit intrinsic properties of level shift operators, properties which stem from the structure of open quantum systems at positive temperatures and which are common to all such systems. They determine the geometry of resonances bifurcating from eigenvalues of positive temperature Hamiltonians and they relate the Gibbs state, the kernel of level shift operators, and zero energy resonances. We show that degeneracy of energy levels of the small part of the open quantum system causes the Fermi Golden Rule Condition to be violated and we analyze ergodic properties of such systems.     

Metric fluctuations,entropy, and the Wheeler-deWitt equation

Quantization using quantum potentials is described in terms of momentum fluctuations, and it is related to Fisher information and entropy. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 1, pp. 32–44, July, 2007.     

Binding energy of impurity states in an inverse parabolic quantum well under magnetic field

 We have investigated the effects of the magnetic field which is directed perpendicular to the well on the binding energy of the hydrogenic impurities in an inverse parabolic quantum well (IPQW) with different widths as well as different Al concentrations at the well center. The Al concentration at the barriers was always x_max=0.3. The calculations were performed within the effective mass approximation, using a variational method. We observe that IPQW structure turns into parabolic quantum well with the inversion effect of the magnetic field and donor impurity binding energy in IPQW strongly depends on the magnetic field, Al concentration at the well center and well dimensions.     

Quantum Key Distribution Using Four-Qubit W State

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 series of key bits by using Bell-state measurements and classical communication.     

Some applications of thermal field theory to quark-gluon plasma

We briefly introduce the thermal field theory within imaginary time formalism, the hard thermal loop perturbation theory and some of its applications to the physics of the quark-gluon plasma, possibly created in relativistic heavy-ion collisions     

负折射指数物质中金属线对电磁波的影响

构造两种结构负折射指数物质(NRM)，利用数值模拟计算两种结构的S参数.由于这种结构尺度比波长小，为精确利用有限积分技术(FIT)进行模拟.通过对这两种结构中金属线位置变化对金属谐振频率影响进行模拟，最后得出由于金属线与谐振环耦合，金属线对称破缺影响谐振环谐振频率和通带，并对等效负折射指数为负的频带产生影响. 关键词： 负折射率 左手物质 通带 金属线对称破缺     

Study of the structural and optical properties of GaN/AlN quantum dot superlattices

We study GaN/AlN Quantum Dot (QD) superlattices utilizing the STREL environment which allows the building of atomistic models, relaxation of the structures, the calculation of the electronic states and optical transitions and the visualization of the results. The forces are calculated using an appropriate Keating or Stillinger–Weber interatomic potential model and the electronic states and optical transitions using a tight-binding formulation which is economical and produces realistic electronic properties. The relaxed structure has strains mainly in the GaN region which are compressive and small tensile strains in the AlN region, mainly below the QD. In the calculation of the electronic states and of the optical transitions the strains are included realistically at the atomistic level. The study of the wavefunctions close to the fundamental gap show how these strains influence the form and spatial extent of the wavefunction. Very close to the fundamental gap the valence and some conduction states are confined in the QD and have considerable oscillator strength.