9,758 research outputs found
Electromagnetically Induced Entanglement
We present a novel quantum phenomenon named electromagnetically induced
entanglement in the conventional Lambda-type three-level atomic system driven
by a strong pump field and a relatively weak probe field. Nearly perfect
entanglement between the pump and probe fields can be achieved with a low
coherence decay rate between the two lower levels, high pump-field intensity,
and large optical depth of the atomic ensemble. The physical origin is quantum
coherence between the lower doublet produced by the pump and probe fields,
similar to the well-known electromagnetically induced transparency. This method
would greatly facilitate the generation of nondegenerate narrow-band
continuous-variable entanglement between bright light beams by using only
coherent laser fields, and may find potential and broad applications in
realistic quantum information processing.Comment: 15pages, 4figure
Observational Constraints on Two-field Warm Inflation
We study the two-field warm inflation models with a double quadratic
potential and a linear temperature dependent dissipative coefficient. We
derived the evolution equation of all kinds of perturbations without assuming
slow-roll approximation, and obtained the curvature power spectrum at the end
of inflation with a fully numerical method. Then we compute the scalar spectral
index , tensor-to-scalar ratio for several representative potentials,
and compare our results with observational data. At last, we use Planck data to
constrain the parameters in our models. This work is a natural extension of
single-field warm inflation, and the aim of this work is to present some
features of multi-field warm inflation using a simple two-field model.Comment: 13 pages, 6 figures. Accepted for publication in Physical Review
Primordial non-Gaussianity in noncanonical warm inflation
We study the bispectrum of the primordial curvature perturbation on
uniform-density hypersurfaces generated by a kind of the noncanonical warm
inflation, wherein the inflation is provided by a noncanonical scalar inflaton
field that is coupled to radiation through a thermal dissipation effect. We
obtain an analytic form for the nonlinear parameter that describes the
non-Gaussianity in first-order cosmological perturbation theory and analyse the
magnitude of this nonlinear parameter. We make a comparison between our result
and those of the standard inflation and the canonical warm inflation. We also
discuss when the contribution to the non-Gaussianity due to the second-order
perturbation theory becomes more important and what effect can be observed. We
take the Dirac-Born-Infeld (DBI) inflation as a concrete example to find how
the sound speed and the thermal dissipation strength to decide the
non-Gaussianity and to get a lower bound of the sound speed constrained by
PLANCK.Comment: 7 pages, 2 figure
Two-field Warm Inflation and Its Scalar Perturbations on Large Scales
We explore the homogeneous background dynamics and the evolution of generated
perturbations of cosmological inflation that is driven by multiple scalar
fields interacting with a perfect fluid.Then we apply the method to warm
inflation driven by two scalar fields and a radiation fluid, and present
general results about the evolution of the inflaton and radiation. After
decomposing the perturbations into adiabatic and entropy modes, we give the
equation of motion of adiabatic and entropy perturbations on large scales.
Then, we give numerical results of background and perturbation equations in a
concrete model (the dissipative coefficient ). At last, we
use the most recent observational data to constrain our models and give the
observationally allowed regions of parameters. This work is a natural extension
of warm inflation to multi-field cases.Comment: 10 pages, 4 figure
Entangler via Electromagnetically Induced Transparency with Atomic Ensembles
We present an efficient and convenient scheme to entangle multiple optical
fields via electromagnetically induced transparency in an atomic ensemble. The
atomic spin wave, produced through electromagnetically induced transparency in
the Lambda-type configuration in an atomic ensemble, can be described by a Bose
operator and acts as the entangler. By using the entangler, any desired number
of nondegenerate narrow-band continuous-variable entangled fields, in
principle, can be generated through stimulated Raman scattering processes,
which holds great promise for applications in scalable quantum communication
and quantum networks.Comment: 14pages, 3figure
Warm inflation in loop quantum cosmology: a model with a general dissipative coefficient
A general form of warm inflation with the dissipative coefficient
in loop quantum cosmology is
studied. In this case, we obtain conditions for the existence of a warm
inflationary attractor in the context of loop quantum cosmology by using the
method of stability analysis. The two cases when the dissipative coefficient is
independent and dependent on temperature are analyzed
specifically. In the latter case, we use the new power spectrum which should be
used when considering temperature dependence in the dissipative coefficient. We
find that the thermal effect is enhanced in the case . As in the standard
inflation in loop quantum cosmology, we also reach the conclusion that quantum
effect leaves a tiny imprint on the cosmic microwave background (CMB) sky.Comment: 12 pages, accepted for publication in Rhys. Rev.
Consistency of the tachyon warm inflationary universe models
This study concerns the consistency of the tachyon warm inflationary models.
A linear stability analysis is performed to find the slow-roll conditions,
characterized by the potential slow-roll (PSR) parameters, for the existence of
a tachyon warm inflationary attractor in the system. The PSR parameters in the
tachyon warm inflationary models are redefined. Two cases, an exponential
potential and an inverse power-law potential, are studied, when the dissipative
coefficient and , respectively. A
crucial condition is obtained for a tachyon warm inflationary model
characterized by the Hubble slow-roll (HSR) parameter , and the
condition is extendable to some other inflationary models as well. A proper
number of e-folds is obtained in both cases of the tachyon warm inflation, in
contrast to existing works. It is also found that a constant dissipative
coefficient is usually not a suitable assumption for a warm
inflationary model.Comment: 10 pages, 0 figures, accepted for publication in Journal of Cosmology
and Astroparticle Physics (JCAP
Entangling light field with mechanical resonator at high temperature
We present a study on how to realize the widely interested optomechanical
entanglement at high temperature. Unlike the majority of the previous
experimental and theoretical researches that consider the entanglement of a
mechanical resonator with a cavity field created by red-detuned continuous-wave
or blue-detuned pulsed driving field, we find that applying blue-detuned
continuous-wave pump field to cavity optomechanical systems can achieve
considerable degrees of quantum entanglement, which is generally challenging to
obtain at high temperature for the known physical systems. The competition
between the induced squeezing-type interaction and the existing decoherence
leads to stable entanglement in dynamically unstable regime. There is a much
more relaxed condition for the existence of entanglement, as compared with the
well-known criterion for neglecting the thermal decoherence on optomechanically
coupled systems. A simple relation about a boundary in the parameter space,
across which the entanglement can exist or not, is found with an analytical
expression for the degree of the achieved entanglement at any temperature,
which is derived for the systems of highly resolved sideband. The studied
scenario with blue-detuned continuous-wave driving field can greatly simplify
the generation of the widely interested optomechanical entanglement of
macroscopic quantum states. Our study also provides the answers to two
fundamentally meaningful open problems: (1) what is the condition for a system
to avoid its loss of quantum entanglement under thermal decoherence? (2) is it
possible to preserve the entanglement in a thermal environment by increasing
the interaction that entangles the subsystems?Comment: 12 pages, 11 figure
Higgs pair signal enhanced in the 2HDM with two degenerate 125 GeV Higgs bosons
We discuss a scenario of the type-II 2HDM in which the
rate of the Higgs pair production is enhanced due to the two nearly degenerate
125 GeV Higgs bosons (, ). Considering various theoretical and
experimental constraints, we figure out the allowed ranges of the trilinear
couplings of these two Higgs bosons and calculate the signal rate of
from the productions of Higgs pairs (, , )
at the LHC. We find that in the allowed parameter space some trilinear Higgs
couplings can be larger than the SM value by an order and the production rate
of can be greatly enhanced. We also consider a
"decoupling" benchmark point where the light CP-even Higgs has a SM-like cubic
self-coupling while other trilinear couplings are very small. With a detailed
simulation on the signal and backgrounds, we find that
in such a "decoupling" scenario the and channels can jointly enhance
the statistical significance to 5 at 14 TeV LHC with an integrated
luminosity of 3000 fb.Comment: 16 pages, 4 figures, 1 tabl
An extension of two-Higgs-doublet model and the excesses of 750 GeV diphoton, muon g-2 and
In this paper we simultaneously explain the excesses of the 750 GeV diphoton,
muon g-2 and in an extension of the two-Higgs-doublet model
(2HDM) with additional vector-like fermions and a CP-odd scalar singlet ()
which is identified as the 750 GeV resonance. This 750 GeV resonance has a
mixing with the CP-odd scalar () in 2HDM, which leads to a coupling between
and the SM particles as well as a coupling between and the vector-like
fermions. Such a mixing and couplings are strongly constrained by
, muon g-2 and the 750 GeV diphoton data. We scan over the
parameter space and find that such an extension can simultaneously account for
the observed excesses of 750 GeV diphoton, muon g-2 and . The 750
GeV resonance decays in exotic modes, such as , ,
and , and its width can be dozens of GeV and is sensitive to
the mixing angle.Comment: 18 pages, 3 figures and references adde
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