449 research outputs found
Orbital entanglement and violation of Bell inequalities in mesoscopic conductors
We propose a spin-independent scheme to generate and detect two-particle
entanglement in a mesoscopic normal-superconductor system. A superconductor,
weakly coupled to the normal conductor, generates an orbitally entangled state
by injecting pairs of electrons into different leads of the normal conductor.
The entanglement is detected via violation of a Bell inequality, formulated in
terms of zero-frequency current cross-correlators. It is shown that the Bell
inequality can be violated for arbitrary strong dephasing in the normal
conductor.Comment: 4 pages, 2 figure
High multiplicity W+jets predictions at NLO
In these proceedings we present results from a recent calculation for the
production of a W boson in conjunction with five jets at next-to-leading order
in perturbative QCD. We also use results at lower multiplicities to extrapolate
the cross section to the same process with six jets.Comment: 5 pages, Proceedings for the DIS2013 conferenc
Application of the Principle of Maximum Conformality to Top-Pair Production
A major contribution to the uncertainty of finite-order perturbative QCD
predictions is the perceived ambiguity in setting the renormalization scale
. For example, by using the conventional way of setting , one obtains the total production cross-section
with the uncertainty \Delta \sigma_{t \bar{t}}/\sigma_{t
\bar{t}}\sim ({}^{+3%}_{-4%}) at the Tevatron and LHC even for the present
NNLO level. The Principle of Maximum Conformality (PMC) eliminates the
renormalization scale ambiguity in precision tests of Abelian QED and
non-Abelian QCD theories. In this paper we apply PMC scale-setting to predict
the cross-section at the Tevatron and LHC
colliders. It is found that remains almost unchanged by
varying within the region of . The convergence
of the expansion series is greatly improved. For the -channel,
which is dominant at the Tevatron, its NLO PMC scale is much smaller than the
top-quark mass in the small -region, and thus its NLO cross-section is
increased by about a factor of two. In the case of the -channel, which is
dominant at the LHC, its NLO PMC scale slightly increases with the subprocess
collision energy , but it is still smaller than for
TeV, and the resulting NLO cross-section is increased by
. As a result, a larger is obtained in comparison
to the conventional scale-setting method, which agrees well with the present
Tevatron and LHC data. More explicitly, by setting GeV, we
predict pb,
pb and pb. [full abstract can be found in the
paper.]Comment: 15 pages, 11 figures, 5 tables. Fig.(9) is correcte
Antenna subtraction with hadronic initial states
The antenna subtraction method for the computation of higher order
corrections to jet observables and exclusive cross sections at collider
experiments is extended to include hadronic initial states. In addition to the
already known antenna subtraction with both radiators in the final state
(final-final antennae), we introduce antenna subtractions with one or two
radiators in the initial state (initial-final or initial-initial antennae). For
those, we derive the phase space factorization and discuss the allowed phase
space mappings at NLO and NNLO. We present integrated forms for all antenna
functions relevant to NLO calculations, and describe the construction of the
full antenna subtraction terms at NLO on two examples. The extension of the
formalism to NNLO is outlined.Comment: 33 pages, 3 figure
Conditional preparation of a quantum state in the continuous variable regime: generation of a sub-Poissonian state from twin beams
We report the first experimental demonstration of conditional preparation of
a non classical state of light in the continuous variable regime. Starting from
a non degenerate OPO which generates above threshold quantum intensity
correlated signal and idler "twin beams", we keep the recorded values of the
signal intensity only when the idler falls inside a band of values narrower
than its standard deviation. By this very simple technique, we generate a
sub-Poissonian state 4.4dB below shot noise from twin beams exhibiting 7.5dB of
noise reduction in the intensity difference.Comment: 4 pages, Accepted in Phys. Rev. Let
Cyclical Quantum Memory for Photonic Qubits
We have performed a proof-of-principle experiment in which qubits encoded in
the polarization states of single-photons from a parametric down-conversion
source were coherently stored and read-out from a quantum memory device. The
memory device utilized a simple free-space storage loop, providing a cyclical
read-out that could be synchronized with the cycle time of a quantum computer.
The coherence of the photonic qubits was maintained during switching operations
by using a high-speed polarizing Sagnac interferometer switch.Comment: 4 pages, 5 figure
Ultra-low threshold CW Triply Resonant OPO in the near infrared using Periodically Poled Lithium Niobate
We have operated a CW triply resonant OPO using a PPLN crystal pumped by a
Nd:YAG laser at 1.06 micron and generating signal and idler modes in the 2-2.3
micron range. The OPO was operated stably in single mode operation over large
periods of time with a pump threshold as low as 500 microwatts.Comment: 7 pages, 5 figures, submitted to JEOS
NNLO phase space master integrals for two-to-one inclusive cross sections in dimensional regularization
We evaluate all phase space master integrals which are required for the total
cross section of generic 2 -> 1 processes at NNLO as a series expansion in the
dimensional regulator epsilon. Away from the limit of threshold production, our
expansion includes one order higher than what has been available in the
literature. At threshold, we provide expressions which are valid to all orders
in terms of Gamma functions and hypergeometric functions. These results are a
necessary ingredient for the renormalization and mass factorization of
singularities in 2 -> 1 inclusive cross sections at NNNLO in QCD.Comment: 37 pages, plus 3 ancillary files containing analytic expressions in
Maple forma
- …