63,953 research outputs found
Electron teleportation with quantum dot arrays
An electron teleportation protocol, inspired by the scenario by Bennett et
al., is proposed in a mesoscopic set-up. A superconducting circuit allows to
both inject and measure entangled singlet electron pairs in an array of three
normal quantum dots. The selection of the teleportation process is achieved in
the steady state with the help of two superconducting dots and appropriate
gating. Teleportation of the electron spin is detected by measuring the
spin-polarized current through the normal dot array. This current is perfectly
correlated to the pair current flowing inside the superconducting circuit. The
classical channel required by Bennett's protocol, which signals the completion
of a teleportation cycle, is identified with the detection of an electron
charge in the superconducting circuit.Comment: revised version, 4 pages, 2 figure
Reduced classical field theories. k-cosymplectic formalism on Lie algebroids
In this paper we introduce a geometric description of Lagrangian and
Hamiltonian classical field theories on Lie algebroids in the framework of
-cosymplectic geometry. We discuss the relation between Lagrangian and
Hamiltonian descriptions through a convenient notion of Legendre
transformation. The theory is a natural generalization of the standard one; in
addition, other interesting examples are studied, mainly on reduction of
classical field theories.Comment: 26 page
Tensor Representation of Spin States
We propose a generalization of the Bloch sphere representation for arbitrary
spin states. It provides a compact and elegant representation of spin density
matrices in terms of tensors that share the most important properties of Bloch
vectors. Our representation, based on covariant matrices introduced by Weinberg
in the context of quantum field theory, allows for a simple parametrization of
coherent spin states, and a straightforward transformation of density matrices
under local unitary and partial tracing operations. It enables us to provide a
criterion for anticoherence, relevant in a broader context such as quantum
polarization of light.Comment: 5 pages + 7 pages of supplementary informatio
Energy spectrum, dissipation and spatial structures in reduced Hall magnetohydrodynamic
We analyze the effect of the Hall term in the magnetohydrodynamic turbulence
under a strong externally supported magnetic field, seeing how this changes the
energy cascade, the characteristic scales of the flow and the dynamics of
global magnitudes, with particular interest in the dissipation.
Numerical simulations of freely evolving three-dimensional reduced
magnetohydrodynamics (RHMHD) are performed, for different values of the Hall
parameter (the ratio of the ion skin depth to the macroscopic scale of the
turbulence) controlling the impact of the Hall term. The Hall effect modifies
the transfer of energy across scales, slowing down the transfer of energy from
the large scales up to the Hall scale (ion skin depth) and carrying faster the
energy from the Hall scale to smaller scales. The final outcome is an effective
shift of the dissipation scale to larger scales but also a development of
smaller scales. Current sheets (fundamental structures for energy dissipation)
are affected in two ways by increasing the Hall effect, with a widening but at
the same time generating an internal structure within them. In the case where
the Hall term is sufficiently intense, the current sheet is fully delocalized.
The effect appears to reduce impulsive effects in the flow, making it less
intermittent.Comment: 17 pages, 10 figure
Anticoherence of spin states with point group symmetries
We investigate multiqubit permutation-symmetric states with maximal entropy
of entanglement. Such states can be viewed as particular spin states, namely
anticoherent spin states. Using the Majorana representation of spin states in
terms of points on the unit sphere, we analyze the consequences of a
point-group symmetry in their arrangement on the quantum properties of the
corresponding state. We focus on the identification of anticoherent states (for
which all reduced density matrices in the symmetric subspace are maximally
mixed) associated with point-group symmetric sets of points. We provide three
different characterizations of anticoherence, and establish a link between
point symmetries, anticoherence and classes of states equivalent through
stochastic local operations with classical communication (SLOCC). We then
investigate in detail the case of small numbers of qubits, and construct
infinite families of anticoherent states with point-group symmetry of their
Majorana points, showing that anticoherent states do exist to arbitrary order.Comment: 15 pages, 5 figure
Semileptonic decays of the Higgs boson at the Tevatron
We examine the prospects for extending the Tevatron reach for a Standard
Model Higgs boson by including the semileptonic Higgs boson decays h --> WW -->
l nu jj for M_h >~ 2 M_W, and h --> W jj --> l nu jj for M_h <~ 2 M_W, where j
is a hadronic jet. We employ a realistic simulation of the signal and
backgrounds using the Sherpa Monte Carlo event generator. We find kinematic
selections that enhance the signal over the dominant W+jets background. The
resulting sensitivity could be an important addition to ongoing searches,
especially in the mass range 120 <~ M_h <~ 150 GeV. The techniques described
can be extended to Higgs boson searches at the Large Hadron Collider.Comment: 68 pages, 19 figure
A technique for constructing spectral reflectance curves from Viking lander camera multispectral data
A technique for evaluating the construction of spectral reflectance curves from multispectral data obtained with the Viking lander cameras is presented. The multispectral data is limited to 6 channels in the wave-length range 0.4 to 1.1 microns, and several of the channels suffer from appreciable out-of-band response. The technique represents the estimated reflectance curves as a linear combination of known basic functions with coefficients determined to minimize the error in the representation, and it permits all channels, with and without out-of-band response, to contribute equally valid information. The technique is evaluated for known spectral reflectance curves of 8 materials felt likely to be present on the Martian surface. The technique provides an essentially exact fit if the the reflectance curve has no pronounced maxima and minima. Even if the curve has pronounced maxima and minima, the fit is good and reveals the most dominant features. Since only 6 samples are available some short period features are lost. This loss is almost certainly due to undersampling rather than out-of-band channel response
Effects of the Generalized Uncertainty Principle on the Inflation Parameters
We investigate the effects of the generalized uncertainty principle on the
inflationary dynamics of the early universe in both standard and braneworld
viewpoint. We choose the Randall-Sundrum II model as our underlying braneworld
scenario. We find that the quantum gravitational effects lead to a spectral
index which is not scale invariant. Also, the amplitude of density fluctuations
is reduced by increasing the strength of quantum gravitational corrections.
However, the tensor-to-scalar ratio increases by incorporation of these quantum
gravity effects. We outline possible manifestations of these quantum gravity
effects in the recent and future observations.Comment: 11 pages, revised version with new references, Accepted for
publication in IJMP
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