34,774 research outputs found
Fault-tolerant linear optics quantum computation by error-detecting quantum state transfer
A scheme for linear optical implementation of fault-tolerant quantum
computation is proposed, which is based on an error-detecting code. Each
computational step is mediated by transfer of quantum information into an
ancilla system embedding error-detection capability. Photons are assumed to be
subjected to both photon loss and depolarization, and the threshold region of
their strengths for scalable quantum computation is obtained, together with the
amount of physical resources consumed. Compared to currently known results, the
present scheme reduces the resource requirement, while yielding a comparable
threshold region.Comment: 9 pages, 7 figure
Controlled Unitary Operation between Two Distant Atoms
We propose a scheme for implementing a controlled unitary gate between two
distant atoms directly communicating through a quantum transmission line. To
achieve our goal, only a series of several coherent pulses are applied to the
atoms. Our scheme thus requires no ancilla atomic qubit. The simplicity of our
scheme may significantly improve the scalability of quantum computers based on
trapped neutral atoms or ions
Quantum Hall Ferromagnetism in a Two-Dimensional Electron System
Experiments on a nearly spin degenerate two-dimensional electron system
reveals unusual hysteretic and relaxational transport in the fractional quantum
Hall effect regime. The transition between the spin-polarized (with fill
fraction ) and spin-unpolarized () states is accompanied
by a complicated series of hysteresis loops reminiscent of a classical
ferromagnet. In correlation with the hysteresis, magnetoresistance can either
grow or decay logarithmically in time with remarkable persistence and does not
saturate. In contrast to the established models of relaxation, the relaxation
rate exhibits an anomalous divergence as temperature is reduced. These results
indicate the presence of novel two-dimensional ferromagnetism with a
complicated magnetic domain dynamic.Comment: 15 pages, 5 figure
Blow-up behavior of collocation solutions to Hammerstein-type volterra integral equations
We analyze the blow-up behavior of one-parameter collocation solutions for Hammerstein-type Volterra integral equations (VIEs) whose solutions may blow up in finite time. To approximate such solutions (and the corresponding blow-up time), we will introduce an adaptive stepsize strategy that guarantees the existence of collocation solutions whose blow-up behavior is the same as the one for the exact solution. Based on the local convergence of the collocation methods for VIEs, we present the convergence analysis for the numerical blow-up time. Numerical experiments illustrate the analysis
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Development Of Third Harmonic Generation As A Short Pulse Probe Of Shock Heated Material
We are studying high-pressure laser produced shock waves in silicon (100). To examine the material dynamics, we are performing pump-probe style experiments utilizing 600 ps and 40 fs laser pulses from a Ti:sapphire laser. Two-dimensional interferometry reveals information about the shock breakout, while third harmonic light generated at the rear surface is used to infer the crystalline state of the material as a function of time. Sustained third harmonic generation (THG) during a similar to 100 kbar shock breakout indicate that the rear surface remains crystalline for at least 3 ns. However, a decrease in THG during a similar to 300 kbar shock breakout suggests a different behavior, which could include a change in crystalline structure.Mechanical Engineerin
Phenomenological Theory of Superconductivity and Magnetism in HoDyNiBC
The coexistence of the superconductivity and magnetism in the
HoDyNiBC is studied by using Ginzburg-Landau theory. This
alloy shows the coexistence and complex interplay of superconducting and
magnetic order. We propose a phenomenological model which includes two magnetic
and two superconducting order parameters accounting for the multi-band
structure of this material. We describe phenomenologically the magnetic
fluctuations and order and demonstrate that they lead to anomalous behavior of
the upper critical field. The doping dependence of in
HoDyNiBC showing a reentrance behavior are analyzed
yielding a very good agreement with experimental data.Comment: 4 pages, 3 figures, REVTeX, submitted to PR
Compressible Sub-Alfvenic MHD turbulence in Low-beta Plasmas
We present a model for compressible sub-Alfvenic isothermal
magnetohydrodynamic (MHD) turbulence in low-beta plasmas and numerically test
it. We separate MHD fluctuations into 3 distinct families - Alfven, slow, and
fast modes. We find that, production of slow and fast modes by Alfvenic
turbulence is suppressed. As a result, Alfven modes in compressible regime
exhibit scalings and anisotropy similar to those in incompressible regime. Slow
modes passively mimic Alfven modes. However, fast modes show isotropy and a
scaling similar to acoustic turbulence.Comment: 4 pages, 8 figures, Phys. Rev. Lett., in pres
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