1,198 research outputs found
Engineering Entanglement: The Fast-Approach Phase Gate
Optimal-control techniques and a fast-approach scheme are used to implement a
collisional control phase gate in a model of cold atoms in an optical lattice,
significantly reducing the gate time as compared to adiabatic evolution while
maintaining high fidelity. New objective functionals are given for which
optimal paths are obtained for evolution that yields a control-phase gate up to
single-atom Rabi shifts. Furthermore, the fast-approach procedure is used to
design a path to significantly increase the fidelity of non-adiabatic transport
in a recent experiment. Also, the entanglement power of phase gates is
quantified.Comment: 7 pages, 4 figures. Phys. Rev. A (in press
On the nature of Coulomb corrections to the e^+e^- pair production in ultrarelativistic heavy-ion collisions
We manifest the origin of the wrong conclusion made by several groups of
authors on the absence of Coulomb corrections to the cross section of the
e^+e^- pair production in ultrarelativistic heavy-ion collisions. The source of
the mistake is connected with an incorrect passage to the limit in the
expression for the cross section. When this error is eliminated, the Coulomb
corrections do not vanish and agree with the results obtained within the
Weizs\"acker-Williams approximation.Comment: 7 pages, LaTe
Incoherent matter-wave solitons
The dynamics of matter-wave solitons in Bose-Einstein condensates (BEC) is
considerably affected by the presence of a surrounding thermal cloud and by
condensate depletion during its evolution. We analyze these aspects of BEC
soliton dynamics, using time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory.
The condensate is initially prepared within a harmonic trap at finite
temperature, and solitonic behavior is studied by subsequently propagating the
TDHFB equations without confinement. Numerical results demonstrate the collapse
of the BEC via collisional emission of atom pairs into the thermal cloud,
resulting in splitting of the initial density into two solitonic structures
with opposite momentum. Each one of these solitary matter waves is a mixture of
condensed and noncondensed particles, constituting an analog of optical
random-phase solitons.Comment: 4 pages, 2 figures, new TDHFB result
Hot Spot model of Nucleon and Double Parton Scattering
We calculate the rate of double parton scattering (DPS) in proton - proton
collisions in the framework of the recently proposed hot spot model of the
nucleon structure. The resulting rate, especially for the case of three hot
spots, appears to be in tension with the current experimental data on DPS at
the LHC.Comment: 12 pages 2 figures 1 tabl
Nonlinear Dynamics in the Resonance Lineshape of NbN Superconducting Resonators
In this work we report on unusual nonlinear dynamics measured in the
resonance response of NbN superconducting microwave resonators. The nonlinear
dynamics, occurring at relatively low input powers (2-4 orders of magnitude
lower than Nb), and which include among others, jumps in the resonance
lineshape, hysteresis loops changing direction and resonance frequency shift,
are measured herein using varying input power, applied magnetic field, white
noise and rapid frequency sweeps. Based on these measurement results, we
consider a hypothesis according to which local heating of weak links forming at
the boundaries of the NbN grains are responsible for the observed behavior, and
we show that most of the experimental results are qualitatively consistent with
such hypothesis.Comment: Updated version (of cond-mat/0504582), 16 figure
Pattern Competition in the Photorefractive Semiconductors
We analytically study the photorefractive Gunn effect in n-GaAs subjected to
two external laser beams which form a moving interference pattern (MIP) in the
semiconductor. When the intensity of the spatially independent part of the MIP,
denoted by , is small, the system has a periodic domain train (PDT),
consistent with the results of linear stability analysis. When is large,
the space-charge field induced by the MIP will compete with the PDT and result
in complex dynamics, including driven chaos via quasiperiodic route
Induced Coherence and Stable Soliton Spiraling
We develop a theory of soliton spiraling in a bulk nonlinear medium and
reveal a new physical mechanism: periodic power exchange via induced coherence,
which can lead to stable spiraling and the formation of dynamical two-soliton
states. Our theory not only explains earlier observations, but provides a
number of predictions which are also verified experimentally. Finally, we show
theoretically and experimentally that soliton spiraling can be controled by the
degree of mutual initial coherence.Comment: 4 pages, 5 figure
Coulomb corrections and multiple e+e- pair production in ultra-relativistic nuclear collisions
We consider the problem of Coulomb corrections to the inclusive cross
section. We show that these corrections in the limiting case of small charge
number of one of the nuclei coincide with those to the exclusive cross section.
Within our approach we also obtain the Coulomb corrections for the case of
large charge numbers of both nuclei.Comment: 7 pages, REVTeX
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