Minimum construction of two-qubit quantum operations

Optimal construction of quantum operations is a fundamental problem in the realization of quantum computation. We here introduce a newly discovered quantum gate, B, that can implement any arbitrary two-qubit quantum operation with minimal number of both two- and single-qubit gates. We show this by giving an analytic circuit that implements a generic nonlocal two-qubit operation from just two applications of the B gate. We also demonstrate that for the highly scalable Josephson junction charge qubits, the B gate is also more easily and quickly generated than the CNOT gate for physically feasible parameters.Comment: 4 page

Massive charged particle's tunneling from spherical charged black hole

We generalize the Parikh-Wilczek scheme to the tunneling of a massive charged particle from a general spherical charged black hole. We obtain that the tunneling probability depends on the energy, the mass and the charge of the particle. In particular, the modified Hawking temperature is related to the charge. Only at the leading order approximation can the standard Hawking temperature be reproduced. We take the Reissner-Nordstr\"{o}m black hole as an example to clarify our points of view, and find that the accumulation of Hawking radiation makes it approach an extreme black hole.Comment: 10 pages, no figures; v2: a minor typo corrected; v3: 11 pages, clarification and reference added, final version to be published in EPL; v4: minor modifications to match the published versio

Optimal quantum circuit synthesis from Controlled-U gates

From a geometric approach, we derive the minimum number of applications needed for an arbitrary Controlled-Unitary gate to construct a universal quantum circuit. A new analytic construction procedure is presented and shown to be either optimal or close to optimal. This result can be extended to improve the efficiency of universal quantum circuit construction from any entangling gate. Specifically, for both the Controlled-NOT and Double-CNOT gates, we develop simple analytic ways to construct universal quantum circuits with three applications, which is the least possible.Comment: 4 pages, 3 figure

Symmetries and Lie algebra of the differential-difference Kadomstev-Petviashvili hierarchy

By introducing suitable non-isospectral flows we construct two sets of symmetries for the isospectral differential-difference Kadomstev-Petviashvili hierarchy. The symmetries form an infinite dimensional Lie algebra.Comment: 9 page

Quantum molecular dynamics simulations for the nonmetal-metal transition in shocked methane

We have performed quantum molecular-dynamics simulations for methane under shock compressions up to 80 GPa. We obtain good agreement with available experimental data for the principal Hugoniot, derived from the equation of state. A systematic study of the optical conductivity spectra, one-particle density of states, and the distributions of the electronic charge over supercell at Hugoniot points shows that the transition of shocked methane to a metallic state takes place close to the density at which methane dissociates significantly into molecular hydrogen and some long alkane chains. Through analyzing the pair correlation function, we predict the chemical picture of the shocked methane. In contrast to usual assumptions used for high pressure modeling of methane, we find that no diamond-like configurations occurs for the whole density-temperature range studied.Comment: Some revisions have been given in response to referees' sugestion

Constraints on Oscillating Quintom from Supernova, Microwave Background and Galaxy Clustering

We consider in this paper a simple oscillating Quintom model of dark energy which has two free parameters and an equation of state oscillating and crossing -1. For low redshifts the equation of state of this model resembles itself similar to the linearly parameterized dark energy, however differ substantially at large redshifts. We fit our model to the observational data separately from the new high redshift supernova observations from the HST/GOODS program and previous supernova, CMB and galaxy clustering. Our results show that because of the oscillating feature of our model the constraints from observations at large redshifts such as CMB become less stringent.Comment: 4 pages, 6 figures Revtex

Predictions on the Development Dimensions of Provincial Tourism Discipline Based on the Artificial Neural Network BP Model

As the tourism industry has gradually become the strategic mainstay industry of the national economy, the scope of the tourism discipline has developed rigorously. This paper makes a predictive study on the development of the scope of Guangdong provincial tourism discipline based on the artificial neural network BP model in order to find out how the branch of tourism studies can better adapt to the development of the tourism industry. The research findings indicate that the BP model can be applied to the predictions of the scope of the tourism discipline and provide a quantitative basis for decision making with regard to the spatial layout and optimal allocation of the tourism discipline