Second Quantization Representation of Quantum Logic Gate Transformations

By using the theory of multimode linear transformation in Fock space, we offer an effective method to study the quantum logic gates based on fermion states. The forms of some basic quantum logic operations are also obtained.     

Complexity,parallel computation and statistical physics

The intuition that a long history is required for the emergence of complexity in natural systems is formalized using the notion of depth. The depth of a system is defined in terms of the number of parallel computational steps needed to simulate it. Depth provides an objective, irreducible measure of history that is applicable to systems of the kind studied in statistical physics. It is argued that physical complexity cannot occur in the absence of substantial depth and that depth is a useful proxy for physical complexity. The ideas are illustrated for a variety of systems in statistical physics. © 2006 Wiley Periodicals, Inc. Complexity 11: 46–64, 2006     

The Computational Complexity of Sandpiles

Journal of Statistical Physics - Given an initial distribution of sand in an Abelian sandpile, what final state does it relax to after all possible avalanches have taken place? In d≥3, we...     

Quantum phase transition of entanglement in Heisenberg spin model with quantized field

In this paper, we investigate the entanglement of a two-spin system with Heisenberg exchange interaction in a quantized field. The pairwise entanglement between bipartite subsystems is obtained. It is shown that the entanglement exhibits a quantum phase transition due to the variation of exchang coupling. Phase diagrams are obtained explicitly. The analogy of the quantum phase transition compared to the case under a classical field are addressed.     

Symbolic Computation Study of （2＋1）-Dimensional Dispersive Long Wave Equations

Seeking exact analytical solutions of nonlinear evolution equations is of fundamental importance in mathematlcal physics. In this paper, based on a constructive algorithm and symbolic computation, abundant new exact solutions of the （2＋1）-dimensional dispersive long wave equations are obtained, among which there are soliton-like solutions, mult-soliton-like solutions and formal periodic solutions, etc. Certain special solutions are considered and some interesting localized structures are revealed.     

Secure multi-party computation made simple

Known secure multi-party computation protocols are quite complex, involving non-trivial mathematical structures and sub-protocols. The purpose of this paper is to present a very simple approach to secure multi-party computation with straight-forward security proofs. This approach naturally yields protocols secure for mixed (active and passive) corruption and general (as opposed to threshold) adversary structures, confirming the previously proved tight bounds in a simpler framework. Due to their simplicity, the described protocols are well-suited for didactic purposes, which is a main goal of this paper.     

An empirical study on similarity-based mating for evolutionary multiobjective combinatorial optimization

We have already proposed a similarity-based mating scheme to recombine extreme and similar parents for evolutionary multiobjective optimization. In this paper, we examine the effect of the similarity-based mating scheme on the performance of evolutionary multiobjective optimization (EMO) algorithms. First we examine which is better between recombining similar or dissimilar parents. Next we examine the effect of biasing selection probabilities toward extreme solutions that are dissimilar from other solutions in each population. Then we examine the effect of dynamically changing the strength of this bias during the execution of EMO algorithms. Computational experiments are performed on a wide variety of test problems for multiobjective combinatorial optimization. Experimental results show that the performance of EMO algorithms can be improved by the similarity-based mating scheme for many test problems.     

Operation of a planar Penning trap

We demonstrate experimentally the confinement of electrons in a novel planar Penning trap. Measurement of the eigenfrequencies of the trapped electron cloud exhibits similar behaviour as in conventional 3-dimensional penning traps. The trap may be of future use in quantum computing schemes using single cold electrons.     

Characterization of iron(II)(α-diimine) chelates and their interactions with anionic, cationic and non-ionic micelles using the separation, spectrophotometric and computational methods

The Fe(II)(α-diimine) chelates as well as diimine ligands were characterized by means of liquid chromatography and capillary electrophoretic methods with the help of molecular computational methods. The diimine ligands: 2,2′-bipyridine as well as 1,10-phenathroline and its derivatives (5-chloro, 5-methyl, 5-nitro, 4,7-dimethyl, 3,4,7,8-tetramethyl, and 4,7-diphenyl) were used. The chelate parameters such as: log P_ow, hydrodynamic radius, molar volume and charge were estimated. The obtained results were used for the characterization of binding of Fe(NN) (NN = α-diimine) chelates to micelles. In the second part of the work by means of spectrophotometery, it was established that the MLCT (metal-to-ligand charge transfer) bands of all Fe(NN) chelates were no solvent sensitive. The decrease in λ_max (blue shift) of MLCT band of Fe(NN) chelates was observed in solutions of charged micelles. It was concluded that the hydrophobicity of Fe(II)(NN) was found to be responsible for the chelate localization into micellar structure, whereas the surface electrostatic potential of the charged micelle was affected the MLCT band of Fe(II)(NN) chelates. To rationalize the observed effect the molecular modeling method was applied. It was established the stability of λ_max of MLCT band of Fe(NN) in solvents is mainly due to the D₃ symmetry of the chelate. In the micellar phase, the distortion of the chelate geometry, thus the distortion of D₃ symmetry from D₃ to C₂ leads to the observed blue shift in λ_max of MLCT band. It was proposed that the blue shift in the MLCT band could be used for estimating the values of the surface potential of micelle and for establishing the relative hydrophobic character of the micellar interface.     

Evolutionary computation of a deterministic switching regressions estimator

Summary  A deterministic switching regressions estimator is evaluated using an evolutionary method based on genetic algorithms. Distinctive aspects of the method include (1) a combination of simple and random chromosomal crossover and (2) extension of the principle of natural selection to internal parameterization. The evolutionary computation duplicates, significantly faster, the results of an existing enumerative method in samples small enough to permit enumeration. It also provides the ability to calculate the estimator in much larger sample sizes than is possible with the enumerative approach. An example problem from the United States gasoline market is given. Funding support provided by the Gerondelis Foundation, Inc. is gratefully acknowledged.