6,725 research outputs found
Quantum Superposition State Production by Continuous Observations and Feedback
We present a protocol for generation of superpositions of states with
distinguishable field amplitudes in an optical cavity by quantum nondemolition
photon number measurements and coherent feeding of the cavity.Comment: RevTex4, 4 pages, 2 figures. Published in Phys. Rev. Lett. with
higher quality figures. The first part of the manuscript, regarding the Fock
state generator, has been remove
Odd Triplet Pairing in clean Superconductor/Ferromagnet heterostructures
We study triplet pairing correlations in clean Ferromagnet (F)/Superconductor
(S) nanojunctions, via fully self consistent solution of the Bogoliubov-de
Gennes equations. We consider FSF trilayers, with S being an s-wave
superconductor, and an arbitrary angle between the magnetizations of
the two F layers. We find that contrary to some previous expectations, triplet
correlations, odd in time, are induced in both the S and F layers in the clean
limit. We investigate their behavior as a function of time, position, and
. The triplet amplitudes are largest at times on the order of the
inverse ``Debye'' frequency, and at that time scale they are long ranged in
both S and F. The zero temperature condensation energy is found to be lowest
when the magnetizations are antiparallel.Comment: Four pages, including four figure
Four-terminal magneto-transport in graphene p-n junctions created by spatially selective doping
In this paper we describe a graphene p-n junction created by chemical doping.
We find that chemical doping does not reduce mobility in contrast to
top-gating. The preparation technique has been developed from systematic
studies about influences on the initial doping of freshly prepared graphene. We
investigated the removal of adsorbates by vacuum treatment, annealing and
compensation doping using NH3. Hysteretic behavior is observed in the electric
field effect due to dipolar adsorbates like water and NH3. Finally we
demonstrate spatially selective doping of graphene using patterned PMMA.
4-terminal transport measurements of the p-n devices reveal edge channel mixing
in the quantum hall regime. Quantized resistances of h/e^2, h/3e^2 and h/15e^2
can be observed as expected from theory.Comment: 18 pages, 5 figure
Explicit coercivity estimates for the linearized Boltzmann and Landau operators
We prove explicit coercivity estimates for the linearized Boltzmann and
Landau operators, for a general class of interactions including any
inverse-power law interactions, and hard spheres. The functional spaces of
these coercivity estimates depend on the collision kernel of these operators.
They cover the spectral gap estimates for the linearized Boltzmann operator
with Maxwell molecules, improve these estimates for hard potentials, and are
the first explicit coercivity estimates for soft potentials (including in
particular the case of Coulombian interactions). We also prove a regularity
property for the linearized Boltzmann operator with non locally integrable
collision kernels, and we deduce from it a new proof of the compactness of its
resolvent for hard potentials without angular cutoff.Comment: 32 page
The TQ equation of the 8 vertex model for complex elliptic roots of unity
We extend our studies of the TQ equation introduced by Baxter in his 1972
solution of the 8 vertex model with parameter given by
from to the more general case of complex
We find that there are several different cases depending on the parity of
and .Comment: 30 pages, LATE
Structure and hydration of membranes embedded with voltage-sensing domains.
Despite the growing number of atomic-resolution membrane protein structures, direct structural information about proteins in their native membrane environment is scarce. This problem is particularly relevant in the case of the highly charged S1-S4 voltage-sensing domains responsible for nerve impulses, where interactions with the lipid bilayer are critical for the function of voltage-activated ion channels. Here we use neutron diffraction, solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations to investigate the structure and hydration of bilayer membranes containing S1-S4 voltage-sensing domains. Our results show that voltage sensors adopt transmembrane orientations and cause a modest reshaping of the surrounding lipid bilayer, and that water molecules intimately interact with the protein within the membrane. These structural findings indicate that voltage sensors have evolved to interact with the lipid membrane while keeping energetic and structural perturbations to a minimum, and that water penetrates the membrane, to hydrate charged residues and shape the transmembrane electric field
Quantum geometry and gravitational entropy
Most quantum states have wavefunctions that are widely spread over the
accessible Hilbert space and hence do not have a good description in terms of a
single classical geometry. In order to understand when geometric descriptions
are possible, we exploit the AdS/CFT correspondence in the half-BPS sector of
asymptotically AdS_5 x S^5 universes. In this sector we devise a
"coarse-grained metric operator" whose eigenstates are well described by a
single spacetime topology and geometry. We show that such half-BPS universes
have a non-vanishing entropy if and only if the metric is singular, and that
the entropy arises from coarse-graining the geometry. Finally, we use our
entropy formula to find the most entropic spacetimes with fixed asymptotic
moments beyond the global charges.Comment: 29 pages, 2 figures; references adde
Matrix Product Eigenstates for One-Dimensional Stochastic Models and Quantum Spin Chains
We show that all zero energy eigenstates of an arbitrary --state quantum
spin chain Hamiltonian with nearest neighbor interaction in the bulk and single
site boundary terms, which can also describe the dynamics of stochastic models,
can be written as matrix product states. This means that the weights in these
states can be expressed as expectation values in a Fock representation of an
algebra generated by operators fulfilling quadratic relations which
are defined by the Hamiltonian.Comment: 11 pages, Late
Weak electricity of the Nucleon in the Chiral Quark-Soliton Model
The induced pseudotensor constant (weak electricity) of the nucleon is
calculated in the framework of the chiral quark soliton model. This quantity
originates from the G-parity violation and hence is proportional to .
We obtain for a value of .Comment: The final version. Accepted for publication in Phys. Rev.
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