27,763 research outputs found
Superluminal propagation of an optical pulse in a Doppler broadened three-state, single channel active Raman gain medium
Using a single channel active Raman gain medium we show a ns
advance time for an optical pulse of s propagating
through a 10 cm medium, a lead time that is comparable to what was reported
previously. In addition, we have verified experimentally all the features
associated with this single channel Raman gain system. Our results show that
the reported gain-assisted superluminal propagation should not be attributed to
the interference between the two frequencies of the pump field.Comment: 4 pages, 3 figure
Alternative scheme for two-qubit conditional phase gate by adiabatic passage under dissipation
We check a recent proposal [H. Goto and K. Ichimura Phys. Rev. A 70, 012305
(2004)] for controlled phase gate through adiabatic passage under the influence
of spontaneous emission and the cavity decay. We show a modification of above
proposal could be used to generate the necessary conditional phase gates in the
two-qubit Grover search. Conditioned on no photon leakage either from the
atomic excited state or from the cavity mode during the gating period, we
numerically analyze the success probability and the fidelity of the two-qubit
conditional phase gate by adiabatic passage. The comparison made between our
proposed gating scheme and a previous one shows that Goto and Ichimura's scheme
is an alternative and feasible way in the optical cavity regime for two-qubit
gates and could be generalised in principle to multi-qubit gates.Comment: to appear in J. Phys.
Spectrum Analysis of the Type Ib Supernova 1999dn: Probable Identifications of C II and H-alpha
Low resolution spectra of SN 1999dn at early times are presented and compared
with synthetic spectra generated with the parameterized supernova
synthetic-spectrum code SYNOW. We find that the spectra of SN 1999dn strongly
resemble those of SN 1997X and SN 1984L, and hence we classify it as a Type Ib
event. Line-identifications are established through spectrum synthesis. Strong
evidence of both H-alpha and C II 6580 is found. We infer that H-alpha appears
first, before the time of maximum brightness, and then is blended with and
finally overwhelmed by the C II line after maximum; this favors a thin
high-velocity hydrogen skin in this Type Ib supernova.Comment: 15 pages, 3 figures. Accepted for publication in Ap
Evidence for the Collective Nature of the Reentrant Integer Quantum Hall States of the Second Landau Level
We report an unexpected sharp peak in the temperature dependence of the
magnetoresistance of the reentrant integer quantum Hall states in the second
Landau level. This peak defines the onset temperature of these states. We find
that in different spin branches the onset temperatures of the reentrant states
scale with the Coulomb energy. This scaling provides direct evidence that
Coulomb interactions play an important role in the formation of these reentrant
states evincing their collective nature
On the Light Curve and Spectrum of SN 2003dh Separated from the Optical Afterglow of GRB 030329
The net optical light curves and spectra of the supernova (SN) 2003dh are
obtained from the published spectra of GRB 030329, covering about 6 days before
SN maximum to about 60 days after. The bulk of the U-band flux is subtracted
from the observed spectra using early-time afterglow templates, because strong
line blanketing greatly depresses the UV and U-band SN flux in a metal-rich,
fast-moving SN atmosphere. The blue-end spectra of the gamma-ray burst
(GRB)connected hypernova SN 1998bw is used to determine the amount of
subtraction. The subtraction of a host galaxy template affects the late-time
results. The derived SN 2003dh light curves are narrower than those of SN
1998bw, rising as fast before maximum, reaching a possibly fainter maximum, and
then declining ~ 1.2-1.4 times faster. We then build UVOIR bolometric SN light
curve. Allowing for uncertainties, it can be reproduced with a spherical ejecta
model of Mej ~ 7+/-3 Msun, KE ~ (3.5+/-1.5)E52 ergs, with KE/Mej ~ 5 following
previous spectrum modelling, and M(Ni56) ~ (0.4 +0.15/-0.1) Msun. This suggests
a progenitor main-sequence mass of about 25-40 Msun, lower than SN 1998bw but
significantly higher than normal Type Ic SNe and the GRB-unrelated hypernova SN
2002ap.Comment: 18 pages, 7 figures, published by Ap
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