48,688 research outputs found
Multichannel wavelength conversion of 40 Gbit/s NRZ DPSK signals in a highly nonlinear dispersion flattened lead silicate fibre
We experimentally demonstrate the wavelength conversion of three wavelength multiplexed 40 Gbit/s Differential Phase Shift Keyed (DPSK) signals in a 2.2m length of highly nonlinear, dispersion tailored W-type lead-silicate optical fibre
Probing the plateau-insulator quantum phase transition in the quantum Hall regime
We report quantum Hall experiments on the plateau-insulator transition in a
low mobility In_{.53} Ga_{.47} As/InP heterostructure. The data for the
longitudinal resistance \rho_{xx} follow an exponential law and we extract a
critical exponent \kappa= .55 \pm .05 which is slightly different from the
established value \kappa = .42 \pm .04 for the plateau transitions. Upon
correction for inhomogeneity effects, which cause the critical conductance
\sigma_{xx}^* to depend marginally on temperature, our data indicate that the
plateau-plateau and plateau- insulator transitions are in the same universality
class.Comment: 4 pages, 4 figures (.eps
Implications of the Optical Observations of Neutron Stars
We show that observations of pulsars with pulsed optical emission indicate
that the peak flux scales according to the magnetic field strength at the light
cylinder. The derived relationships indicate that the emission mechanism is
common across all of the observed pulsars with periods ranging from 33ms to 385
ms and ages of 1000-300,000 years. It is noted that similar trends exist for
ray pulsars. Furthermore the model proposed by Pacini (1971) and
developed by Pacini and Salvati (1983,1987) still has validity and gives an
adequate explanation of the optical phenomena.Comment: 23 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Thermal Charm Production in Quark-Gluon Plasma at LHC
Charm production from the quark-gluon plasma created in the midrapidity of
central heavy ion collisions at the Large Hadron Collider (LHC) is studied in
the next-to-leading order in QCD. Using a schematic longitudinally
boost-invariant and transversally expanding fire-cylinder model, we find that
charm production could be appreciably enhanced at LHC as a result of the high
temperature that is expected to be reached in the produced quark-gluon plasma.
Sensitivities of our results to the number of charm quark pairs produced from
initial hard scattering, the initial thermalization time and temperature of the
quark-gluon plasma, and the charm quark mass are also studied.Comment: 8 pages, 9 figures; adding a figure and relevant discussion on the
sensitivity of our results to the number of charm quark pairs produced from
initial hard scattering. Version accepted for publication in PR
Model analysis of thermal UV-cutoff effects on the chiral critical surface at finite temperature and chemical potential
We study the effects of temporal UV-cutoff on the chiral critical surface in
hot and dense QCD using a chiral effective model. Recent lattice QCD
simulations indicate that the curvature of the critical surface might change
toward the direction in which the first order phase transition becomes stronger
on increasing the number of lattice sites. To investigate this effect on the
critical surface in an effective model approach, we use the Nambu-Jona-Lasinio
model with finite Matsubara frequency summation. We find that qualitative
feature of the critical surface does not alter appreciably as we decrease the
summation number, which is unlike the case what is observed in the recent
lattice QCD studies. This may either suggest the dependence of chemical
potential on the coupling strength or due to some additional interacting terms
such as vector interactions which could play an important role at finite
density.Comment: 7 pages, 8 figure
Entanglement in bosonic systems
We present a technique to resolve a Gaussian density matrix and its time
evolution through known expectation values in position and momentum. Further we
find the full spectrum of this density matrix and apply the technique to a
chain of harmonic oscillators to find agreement with conformal field theory in
this domain. We also observe that a non-conformal state has a divergent
entanglement entropy.Comment: 7 pages, 6 figure
Generation and control of Greenberger-Horne-Zeilinger entanglement in superconducting circuits
Going beyond the entanglement of microscopic objects (such as photons, spins,
and ions), here we propose an efficient approach to produce and control the
quantum entanglement of three macroscopic coupled superconducting qubits. By
conditionally rotating, one by one, selected Josephson charge qubits, we show
that their Greenberger-Horne-Zeilinger (GHZ) entangled states can be
deterministically generated. The existence of GHZ correlations between these
qubits could be experimentally demonstrated by effective single-qubit
operations followed by high-fidelity single-shot readouts. The possibility of
using the prepared GHZ correlations to test the macroscopic conflict between
the noncommutativity of quantum mechanics and the commutativity of classical
physics is also discussed.Comment: 4 Pages with 1 figure. to appear in Physical Review Letter
- …