765 research outputs found
Generating Polarization-Entangled Photon Pairs with Arbitrary Joint Spectrum
We present a scheme for generating polarization-entangled photons pairs with
arbitrary joint spectrum. Specifically, we describe a technique for spontaneous
parametric down-conversion in which both the center frequencies and the
bandwidths of the down-converted photons may be controlled by appropriate
manipulation of the pump pulse. The spectral control offered by this technique
permits one to choose the operating wavelengths for each photon of a pair based
on optimizations of other system parameters (loss in optical fiber, photon
counter performance, etc.). The combination of spectral control, polarization
control, and lack of group-velocity matching conditions makes this technique
particularly well-suited for a distributed quantum information processing
architecture in which integrated optical circuits are connected by spans of
optical fiber.Comment: 6 pages, 3 figure
Symmetric Autocompensating Quantum Key Distribution
We present quantum key distribution schemes which are autocompensating
(require no alignment) and symmetric (Alice and Bob receive photons from a
central source) for both polarization and time-bin qubits. The primary benefit
of the symmetric configuration is that both Alice and Bob may have passive
setups (neither Alice nor Bob is required to make active changes for each run
of the protocol). We show that both the polarization and the time-bin schemes
may be implemented with existing technology. The new schemes are related to
previously described schemes by the concept of advanced waves.Comment: 4 pages, 2 figur
Polarization-sensitive quantum-optical coherence tomography
We set forth a polarization-sensitive quantum-optical coherence tomography
(PS-QOCT) technique that provides axial optical sectioning with
polarization-sensitive capabilities. The technique provides a means for
determining information about the optical path length between isotropic
reflecting surfaces, the relative magnitude of the reflectance from each
interface, the birefringence of the interstitial material, and the orientation
of the optical axis of the sample. PS-QOCT is immune to sample dispersion and
therefore permits measurements to be made at depths greater than those
accessible via ordinary optical coherence tomography. We also provide a general
Jones matrix theory for analyzing PS-QOCT systems and outline an experimental
procedure for carrying out such measurements.Comment: 15 pages, 5 figures, to appear in Physical Review
Simple model for 1/f noise
We present a simple stochastic mechanism which generates pulse trains
exhibiting a power law distribution of the pulse intervals and a
power spectrum over several decades at low frequencies with close to
one. The essential ingredient of our model is a fluctuating threshold which
performs a Brownian motion. Whenever an increasing potential hits the
threshold, is reset to the origin and a pulse is emitted. We show that
if increases linearly in time, the pulse intervals can be approximated
by a random walk with multiplicative noise. Our model agrees with recent
experiments in neurobiology and explains the high interpulse interval
variability and the occurrence of noise observed in cortical
neurons and earthquake data.Comment: 4 pages, 4 figure
Non-classical Photon Statistics For Two-mode Optical Fields
The non-classical property of subpoissonian photon statistics is extended
from one to two-mode electromagnetic fields, incorporating the physically
motivated property of invariance under passive unitary transformations.
Applications to squeezed coherent states, squeezed thermal states, and
superposition of coherent states are given. Dependences of extent of
non-classical behaviour on the independent squeezing parameters are graphically
displayed.Comment: 15 pages, RevTex, 5 figures, available by sending email to
[email protected]
Parity-dependent squeezing of light
A parity-dependent squeezing operator is introduced which imposes different
SU(1,1) rotations on the even and odd subspaces of the harmonic oscillator
Hilbert space. This operator is used to define parity-dependent squeezed states
which exhibit highly nonclassical properties such as strong antibunching,
quadrature squeezing, strong oscillations in the photon-number distribution,
etc. In contrast to the usual squeezed states whose and Wigner functions
are simply Gaussians, the parity-dependent squeezed states have much more
complicated and Wigner functions that exhibit an interesting interference
in phase space. The generation of these states by parity-dependent quadratic
Hamiltonians is also discussed.Comment: accepted for publication in J. Phys. A, LaTeX, 11 pages, 12 figures
(compressed PostScript, available at
http://www.technion.ac.il/~brif/graphics/pdss_graph ). More information on
http://www.technion.ac.il/~brif/science.htm
Single Cooper pair tunneling induced by non-classical microwaves
A mesoscopic Josephson junction interacting with a mode of non-classical
microwaves with frequency is considered. Squeezing of the
electromagnetic field drastically affects the dynamics of Cooper tunneling. In
particular, Bloch steps can be observed even when the microwaves are in the
squeezed vacuum state with {\em zero} average amplitude of the field . The interval between these steps is double in size in
comparison to the conventional Bloch steps.Comment: 8 pages, 2 figures are available upon request to:
[email protected]
Malignant myelomonocytic cells after in vitro infection of marrow cells with Friend leukaemia virus.
Infection of long-term BDF1 marrow cultures with Friend leukaemia virus complex (FLV) induced transformed cells with myelomonocytic characteristics, which were isolated only 14 days after the viral infection. Criteria for transformation were growth in suspension cultures and high plating efficiency in agar. The lymphatic leukaemia virus (LLV) replicates in these suspension cultures, but the spleen focus-forming virus (SFFV) component of the FLV complex has not been detected. Injection of the transformed cells into syngeneic neonatal or adult mice leads to the development of leukaemia which can be demonstrated to be of donor origin by the presence of two metacentric marker chromosomes which are also seen in the cultured cells
Observation of bosonic coalescence of photon pairs
Quantum theory predicts that two indistinguishable photons incident on a
beam-splitter interferometer stick together as they exit the device (the pair
emerges randomly from one port or the other). We use a special
photon-number-resolving energy detector for a direct loophole-free observation
of this quantum-interference phenomenon. Simultaneous measurements from two
such detectors, one at each beam-splitter output port, confirm the absence of
cross-coincidences.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Diagnosis and outcome of oesophageal Crohn's disease
BACKGROUND AND AIMS:
Crohn's disease (CD) can involve any part of the gastrointestinal tract. We aimed to characterize clinical, endoscopic, histologic features and treatment outcomes of CD patients with oesophageal involvement.
METHODS:
We collected cases through a retrospective multicentre European Crohn's and Colitis Organisation CONFER [COllaborative Network For Exceptionally Rare case reports] project. Clinical data were recorded in a standardized case report form.
RESULTS:
A total of 40 patients were reported [22 males, mean (±SD, range) age at oesophageal CD diagnosis: 25 (±13.3, 10-71) years and mean time of follow-up: 67 (±68.1, 3-240) months]. Oesophageal involvement was established at CD diagnosis in 26 patients (65%) and during follow-up in 14. CD was exclusively located in the oesophagus in 2 patients. Thirteen patients (32.2%) were asymptomatic at oesophageal disease diagnosis. Oesophageal strictures were present in 5 patients and fistulizing oesophageal disease in one. Eight patients exhibited granulomas on biopsies. Proton-pump inhibitors (PPIs) were administered in 37 patients (92.5%). Three patients underwent endoscopic dilation for symptomatic strictures and none oesophageal-related surgery. Diagnosis in pre-established CD resulted in treatment modifications in 9/14 patients. Clinical remission of oesophageal disease was seen in 33/40 patients (82.5%) after a mean time of 7 (±5.6, 1-18) months. Follow-up endoscopy was performed in 29/40 patients and 26/29 (89.7%) achieved mucosal healing.
CONCLUSION:
In this case series the endoscopic and histologic characteristics of isolated oesophageal CD were similar to those reported in other sites of involvement. Treatment was primarily conservative, with PPIs administered in the majority of patients and modifications in pre-existing IBD-related therapy occurring in two thirds of them. Clinical and endoscopic remission was achieved in more than 80% of the patients.info:eu-repo/semantics/publishedVersio
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