3,173 research outputs found
Quantum interference with beamlike type-II spontaneous parametric down-conversion
We implement experimentally a method to generate photon-numberpath and
polarization entangled photon pairs using ``beamlike'' type-II spontaneous
parametric down-conversion (SPDC), in which the signal-idler photon pairs are
emitted as two separate circular beams with small emission angles rather than
as two diverging cones.Comment: 4 pages, two-colum
How Could the Proton Transversity be Measured
The perspectives of two new nonstandard methods of transversal quark
polarization measurement are considered: the jet handedness and the so-called
"Collins effect" due to spin dependent T-odd fragmentation function responsible
for the left-right asymmetry in fragmenting of transversally polarized quarks.
Recent experimental indications in favor of these effects are observed: 1.The
correlation of the T-odd one-particle fragmentation functions found by DELPHI
in -jet decay. Integrated over the fraction of longitudinal and
transversal momenta, this correlation is of 1.6% order, which means order of
13% for the analyzing power. 2.A rather large () handedness
transversal to the production plane observed in the diffractive production of
() triples from nuclei by the --beam.
It shows a clear dynamic origin and resembles the single spin asymmetry
behavior.
All this makes us hope to use these effects in polarized DIS experiments for
transversity measurement. The first estimation of transversity was done by
using the azimuthal asymmetry in semi-inclusive DIS recently measured by HERMES
and SMC.Comment: 8 pages, Latex, czjphys2.sty. Talk at Int. Workshop "PRAHA-SPIN99",
Prague 6-11 Sept 1999. To appear in Czech.J.Phys Supp
M-Theory Giant Gravitons with C field
We find giant graviton configurations of an M5-brane probe in the D=11
supergravity background generated by a stack of non-threshold (M2,M5) bound
states. The M5-brane probe shares three directions with the background and
wraps a two-sphere transverse to the bound states. For a particular value of
the worldvolume gauge field of the PST formalism, there exist solutions of the
equations of motion for which the M5-brane probe behaves as a wave propagating
in the (M2,M5) background. We have checked that the probe breaks the
supersymmetry of the background exactly as a massless particle moving along the
trajectory of its center of mass.Comment: 11 pages, LaTeX; v2: references adde
Role of many-body entanglement in decoherence processes
A pure state decoheres into a mixed state as it entangles with an
environment. When an entangled two-mode system is embedded in a thermal
environment, however, each mode may not be entangled with its environment by
their simple linear interaction. We consider an exactly solvable model to study
the dynamics of a total system, which is composed of an entangled two-mode
system and a thermal environment, and also an array of infinite beam splitters.
It is shown that many-body entanglement of the system and the environment plays
a crucial role in the process of disentangling the system.Comment: 4 pages, 1 figur
Interferometric Bell-state preparation using femtosecond-pulse-pumped Spontaneous Parametric Down-Conversion
We present theoretical and experimental study of preparing maximally
entangled two-photon polarization states, or Bell states, using femtosecond
pulse pumped spontaneous parametric down-conversion (SPDC). First, we show how
the inherent distinguishability in femtosecond pulse pumped type-II SPDC can be
removed by using an interferometric technique without spectral and amplitude
post-selection. We then analyze the recently introduced Bell state preparation
scheme using type-I SPDC. Theoretically, both methods offer the same results,
however, type-I SPDC provides experimentally superior methods of preparing Bell
states in femtosecond pulse pumped SPDC. Such a pulsed source of highly
entangled photon pairs is useful in quantum communications, quantum
cryptography, quantum teleportation, etc.Comment: 11 pages, two-column format, to appear in PR
Old and new parton distribution and fragmentation functions
A short review of problems with parton distribution functions in nucleons,
non-polarized and polarized, is given. The main part is devoted to the
transversity distribution its possible measurement and its first experimental
probe via spin asymmetry in semi-inclusive DIS. It is argued that the proton
transversity distribution could be successfully measured in future DIS
experiments with {\it longitudinally} polarized target.Comment: 9 pages, latex, czjphys2.sty, 4 eps figures. Submitted at 35-th
Rancontre de Moriond, March 2000 and at Praha-SPIN-2000, July 2000. To be
published in Czechoslovak J. Phys. (Suppl) 51 (2001
The chirally-odd twist-3 distribution function e(x) in the chiral quark-soliton model
The chirally-odd twist-3 nucleon distribution e(x) is studied in the large-Nc
limit in the framework of the chiral quark-soliton model at a low normalization
point of about 0.6 GeV. The remarkable result is that in the model e(x)
contains a delta-function-type singularity at x=0. The regular part of e(x) is
found to be sizeable at the low scale of the model and in qualitative agreement
with bag model calculations.Comment: 16 pages, 6 figures, revtex, Ref.[50] and footnote 3 adde
First-order interference of nonclassical light emitted spontaneously at different times
We study first-order interference in spontaneous parametric down-conversion
generated by two pump pulses that do not overlap in time. The observed
modulation in the angular distribution of the signal detector counting rate can
only be explained in terms of a quantum mechanical description based on
biphoton states. The condition for observing interference in the signal channel
is shown to depend on the parameters of the idler radiation.Comment: 5 pages, two-column, submitted to PR
Clapping modes in unconventional superconductors
We consider a superconducting state with a mixed symmetry order parameter
components, e.g. or with . We argue for the
existence of the new orbital magnetization mode which corresponds to the
oscillations of relative phase between two components around an
equilibrium value of . It is similar to the so called
``clapping'' mode in superfluid . We estimate the frequency of this
mode depending on the field and temperature for the specific
case of magnetic field induced state. We find that this mode is {\em
tunable} with an applied magnetic field with \omega_0(B,T) \propto B \0,
where \0 is the magnitude of the d-wave order parameter. We argue also that
similar filed induced clapping mode should be present in an organic p-wave
superconductors.Comment: M2S-HTSC-VI Proceedings, Feb 2000, Houston, TX, USA; 4 pages. Physica
C, to be publishe
Tailoring Single and Multiphoton Probabilities of a Single Photon On-Demand Source
As typically implemented, single photon sources cannot be made to produce
single photons with high probability, while simultaneously suppressing the
probability of yielding two or more photons. Because of this, single photon
sources cannot really produce single photons on demand. We describe a
multiplexed system that allows the probabilities of producing one and more
photons to be adjusted independently, enabling a much better approximation of a
source of single photons on demand.Comment: 4 pages, LaTex, 2 figures, twocolumn and RevTex Style for PR
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