2,945 research outputs found
False Vacuum in the Supersymmetric Mass Varying Neutrinos Model
We present detailed analyses of the vacuum structure of the scalar potential
in a supersymmetric Mass Varying Neutrinos model. The observed dark energy
density is identified with false vacuum energy and the dark energy scale of
order is understood by gravitationally suppressed supersymmetry
breaking scale, , in the model. The vacuum expectation
values of sneutrinos should be tiny in order that the model works. Some decay
processes of superparticles into acceleron and sterile neutrino are also
discussed in the model.Comment: 7 pages, 5 figures, revtex, typos correcte
Efficient-phase-encoding protocols for continuous-variable quantum key distribution using coherent states and postselection
We propose efficient-phase-encoding protocols for continuous-variable quantum
key distribution using coherent states and postselection. By these phase
encodings, the probability of basis mismatch is reduced and total efficiency is
increased. We also propose mixed-state protocols by omitting a part of
classical communication steps in the efficient-phase-encoding protocols. The
omission implies a reduction of information to an eavesdropper and possibly
enhances the security of the protocols. We investigate the security of the
protocols against individual beam splitting attack.Comment: RevTeX4, 8 pages, 9 figure
Entanglement Spectra of the quantum hard-square model: Holographic minimal models
We study the entanglement properties of a quantum lattice-gas model for which
we can find the exact ground state (of the Rokhsar-Kivelson type). The ground
state can be expressed as a superposition of states, each of which is
characterized by a particle configuration with nearest-neighbor exclusion. We
show that the reduced density matrix of the model on a ladder is intimately
related to the transfer matrix of the classical hard-square model. The
entanglement spectra of the model on square and triangular ladders are critical
when parameters are chosen so that the corresponding classical hard-square
models are critical. A detailed analysis reveals that the critical theories for
the entanglement Hamiltonians are minimal conformal field theories. We
further show that the entanglement Hamiltonian for the triangular ladder is
integrable despite the fact that the original quantum lattice-gas model is
non-integrable.Comment: 10 pages, 8 figure
Low Energy Theorem for SUSY Breaking with Gauge Supermultiplets
Low energy theorems of Nambu-Goldstone fermion associated with spontaneously
broken supersymmetry are studied for gauge supermultiplets. Two possible terms
in the effective Lagrangian are needed to deal with massless gaugino and/or
massless gauge boson. As an illustrative example, a concrete model is worked
out which can interpolate massless as well as massive gaugino and/or gauge
boson to examine the low energy effective interaction of NG-fermion.Comment: 14page
Analysis of an experimental quantum logic gate by complementary classical operations
Quantum logic gates can perform calculations much more efficiently than their
classical counterparts. However, the level of control needed to obtain a
reliable quantum operation is correspondingly higher. In order to evaluate the
performance of experimental quantum gates, it is therefore necessary to
identify the essential features that indicate quantum coherent operation. In
this paper, we show that an efficient characterization of an experimental
device can be obtained by investigating the classical logic operations on a
pair of complementary basis sets. It is then possible to obtain reliable
predictions about the quantum coherent operations of the gate such as
entanglement generation and Bell state discrimination even without performing
these operations directly.Comment: 14 pages, 1 figure, 3 tables, Brief Review for Modern Physics Letters
A, includes a more detailed analysis of the experimental data in Phys. Rev.
Lett. 95, 210506 (2005) (quant-ph/0506263). v2 has minor corrections in
layou
Fidelity criterion for quantum-domain transmission and storage of coherent states beyond unit-gain constraint
We generalize the experimental success criterion for quantum
teleportation/memory in continuous-variable quantum systems to be suitable for
non-unit-gain condition by considering attenuation/amplification of the
coherent-state amplitude. The new criterion can be used for a non-ideal quantum
memory and long distance quantum communication as well as quantum devices with
amplification process. It is also shown that the framework to measure the
average fidelity is capable of detecting all Gaussian channels in quantum
domain.Comment: 4pages, No figures, Accepted for publication in PR
Observable non-gaussianity from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis
In any realistic particle physics model of inflation, the inflaton can be
expected to couple to other fields. We consider a model with a dilaton-like
coupling between a U(1) gauge field and a scalar inflaton. We show that this
coupling can result in observable non-gaussianity, even in the conventional
regime where inflation is supported by a single scalar slowly rolling on a
smooth potential: the time dependent inflaton condensate leads to amplification
of the large-scale gauge field fluctuations, which can feed-back into the
scalar/tensor cosmological perturbations. In the squeezed limit, the resulting
bispectrum is close to the local one, but it shows a sizable and characteristic
quadrupolar dependence on the angle between the shorter and the larger modes in
the correlation. Observable non-gaussianity is obtained in a regime where
perturbation theory is under control. If the gauge field is identified with the
electromagnetic field, the model that we study is a realization of the
magnetogenesis idea originally proposed by Ratra, and widely studied. This
identification (which is not necessary for the non-gaussianity production) is
however problematic in light of a strong coupling problem already noted in the
literature.Comment: 28 pages, no figures. Final versio
More anomaly-free models of six-dimensional gauged supergravity
We construct a huge number of anomaly-free models of six-dimensional N =
(1,0) gauged supergravity. The gauge groups are products of U(1) and SU(2), and
every hyperino is charged under some of the gauge groups. It is also found that
the potential may have flat directions when the R-symmetry is diagonally gauged
together with another gauge group. In an appendix, we determine the
contribution to the global SU(2) anomaly from symplectic Majorana Weyl fermions
in six dimensions.Comment: 20 pages, v3: published versio
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