4,463 research outputs found
Experimental Realization of Asymmetric Phase-Covariant Quantum Cloning
While exact cloning of an unknown quantum state is prohibited by the
linearity of quantum mechanics, approximate cloning is possible and has been
used, e.g., to derive limits on the security of quantum communication
protocols. In the case of asymmetric cloning, the information from the input
state is distributed asymmetrically between the different output states. Here,
we consider asymmetric phase-covariant cloning, where the goal is to optimally
transfer the phase information from a single input qubit to different output
qubits. We construct an optimal quantum cloning machine for two qubits that
does not require ancilla qubits and implement it on an NMR quantum information
processor.Comment: 6 pages, 5 figure
Quantum Electrodynamics near a Dielectric Half-space
We determine the photon propagator in the presence of a non-dispersive
dielectric half-space and use it to calculate the self-energy of an electron
near a dielectric surface
Quantifying Changes in the Spatial Structure of Trabecular Bone
We apply recently introduced measures of complexity for the structural
quantfication of distal tibial bone. For the first time, we are able to
investigate the temporal structural alteration of trabecular bone. Based on
four patients, we show how bone may alter due to temporal immobilisation
Formation of Polymorphic Cluster Phases for Purely Repulsive Soft Spheres
We present results from density functional theory and computer simulations
that unambiguously predict the occurrence of first-order freezing transitions
for a large class of ultrasoft model systems into cluster crystals. The
clusters consist of fully overlapping particles and arise without the existence
of attractive forces. The number of particles participating in a cluster scales
linearly with density, therefore the crystals feature density-independent
lattice constants. Clustering is accompanied by polymorphic bcc-fcc
transitions, with fcc being the stable phase at high densities.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Magnetic Field-Induced Lattice Effects in a Quasi-2D Organic Conductor Close to the Mott Metal-Insulator Transition
We present ultra-high-resolution dilatometric studies in magnetic fields on a
quasi-two-dimensional organic conductor
-(D8-BEDT-TTF)Cu[N(CN)]Br, which is located close to the
Mott metal-insulator (MI) transition. The obtained thermal expansion
coefficient, , reveals two remarkable features: (i) the Mott MI
transition temperature = (13.6 0.6)\,K is insensitive to fields
up to 10\,T, the highest applied field; (ii) for fields along the interlayer
\emph{b}-axis, a magnetic-field-induced (FI) phase transition at =
(9.5 0.5)\,K is observed above a threshold field 1 T,
indicative of a spin reorientation with strong magneto-elastic coupling.Comment: 5 pages, 4 figure
Direct Measurement of 2D and 3D Interprecipitate Distance Distributions from Atom-Probe Tomographic Reconstructions
Edge-to-edge interprecipitate distance distributions are critical for
predicting precipitation strengthening of alloys and other physical phenomena.
A method to calculate this 3D distance and the 2D interplanar distance from
atom-probe tomographic data is presented. It is applied to nanometer-sized
Cu-rich precipitates in an Fe-1.7 at.% Cu alloy. Experimental interprecipitate
distance distributions are discussed
From Type IIA Black Holes to T-dual Type IIB D-Instantons in N=2, D=4 Supergravity
We discuss the T-duality between the solutions of type IIA versus IIB
superstrings compactified on Calabi-Yau threefolds. Within the context of the
N=2, D=4 supergravity effective Lagrangian, the T-duality transformation is
equivalently described by the c-map, which relates the special Kahler moduli
space of the IIA N=2 vector multiplets to the quaternionic moduli space of the
N=2 hyper multiplets on the type IIB side (and vice versa). Hence the
T-duality, or c-map respectively, transforms the IIA black hole solutions,
originating from even dimensional IIA branes, of the special Kahler effective
action, into IIB D-instanton solutions of the IIB quaternionic sigma-model
action, where the D-instantons can be obtained by compactifying odd IIB
D-branes on the internal Calabi-Yau space. We construct via this mapping a
broad class of D-instanton solutions in four dimensions which are determinded
by a set of harmonic functions plus the underlying topological Calabi-Yau data.Comment: LaTeX, 37 pages. Some typos fixed. Final version, to appear in Nucl.
Phys.
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