25,890 research outputs found
Representation of quantum states as points in a probability simplex associated to a SIC-POVM
The quantum state of a -dimensional system can be represented by the
probabilities corresponding to a SIC-POVM, and then this distribution of
probability can be represented by a vector of in a simplex, we
will call this set of vectors . Other way of represent a
-dimensional system is by the corresponding Bloch vector also in
, we will call this set of vectors . In this paper it
is proved that with the adequate scaling . Also we
indicate some features of the shape of .Comment: 12 pages. Added journal referenc
High purith low defect FZ silicon
The most common intrinsic defects in dislocation-free float zone (FZ) silicon crystals are the A- and B-type swirl defects. The mechanisms of their formation and annihilation have been extensively studied. Another type of defect in dislocation-free FZ crystals is referred to as a D-type defect. Concentrations of these defects can be minimized by optimizing the growth conditions, and the residual swirls can be reduced by the post-growth extrinsic gettering process. Czochralski (Cz) silicon wafers are known to exhibit higher resistance to slip and warpage due to thermal stress than do FZ wafers. The Cz crystals containing dislocations are more resistant to dislocation movement than dislocated FZ crystals because of the locking of dislocations by oxygen atoms present in the Cz crystals. Recently a transverse magnetic field was applied during the FZ growth of extrinsic silicon. Resultant flow patterns, as revealed by striation etching and spreading resistance in Ga-doped silicon crystals, indicate strong effects of the transverse magnetic field on the circulation within the melt. At fields of 5500 gauss, the fluid flow in the melt volume is so altered as to affect the morphology of the growing crystal
Magnetic structure of Ba(TiO)Cu(PO) probed using spherical neutron polarimetry
The antiferromagnetic compound Ba(TiO)Cu(PO) contains square
cupola of corner-sharing CuO plaquettes, which were proposed to form
effective quadrupolar order. To identify the magnetic structure, we have
performed spherical neutron polarimetry measurements. Based on symmetry
analysis and careful measurements we conclude that the orientation of the
Cu spins form a non-collinear in-out structure with spins approximately
perpendicular to the CuO motif. Strong Dzyaloshinskii-Moriya interaction
naturally lends itself to explain this phenomenon. The identification of the
ground state magnetic structure should serve well for future theoretical and
experimental studies into this and closely related compounds.Comment: 9 pages, 4 figure
Chiral Zeromodes on Vortex-type Intersecting Heterotic Five-branes
We solve the gaugino Dirac equation on a smeared intersecting five-brane
solution in E_8\times E_8 heterotic string theory to search for localized
chiral zeromodes on the intersection. The background is chosen to depend on the
full two-dimensional overall transverse coordinates to the branes. Under some
appropriate boundary conditions, we compute the complete spectrum of zeromodes
to find that, among infinite towers of Fourier modes, there exist only three
localized normalizable zeromodes, one of which has opposite chirality to the
other two. This agrees with the result previously obtained in the domain-wall
type solution, supporting the claim that there exists one net chiral zeromode
localized on the heterotic five-brane system.Comment: 10 pages, 2 figure
Charged rotating Kaluza-Klein multi-black holes and multi-black strings in five-dimensional Einstein-Maxwell theory
We construct exact solutions, which represent regular charged rotating
Kaluza-Klein multi-black holes in the five-dimensional pure Einstein-Maxwell
theory. Quantization conditions between the mass, the angular momentum, and
charges appear from the regularity condition of horizon. We also obtain
multi-black string solutions by taking some limits in the solutions. We extend
the black hole solutions to the five-dimensional Einstein-Maxwell-Chern-Simons
theory with an arbitrary Chern-Simons coupling constant.Comment: 14 pages. arXiv admin note: substantial text overlap with
arXiv:1206.481
Surface Shubnikov-de Hass oscillations and non-zero Berry phases of the topological hole conduction in TlBiSe
We report the observation of two-dimensional Shubnikov-de Hass (SdH)
oscillations in the topological insulator TlBiSe. Hall
effect measurements exhibited electron-hole inversion in samples with bulk
insulating properties. The SdH oscillations accompanying the hole conduction
yielded a large surface carrier density of /cm, with the Landau-level fan diagram exhibiting the
Berry phase. These results showed the electron-hole reversibility around the
in-gap Dirac point and the hole conduction on the surface Dirac cone without
involving the bulk metallic conduction.Comment: 5 pages, 4 figure
Lazy states: sufficient and necessary condition for zero quantum entropy rates under any coupling to the environment
We find the necessary and sufficient conditions for the entropy rate of the
system to be zero under any system-environment Hamiltonian interaction. We call
the class of system-environment states that satisfy this condition lazy states.
They are a generalization of classically correlated states defined by quantum
discord, but based on projective measurements of any rank. The concept of lazy
states permits the construction of a protocol for detecting global quantum
correlations using only local dynamical information. We show how quantum
correlations to the environment provide bounds to the entropy rate, and how to
estimate dissipation rates for general non-Markovian open quantum systems.Comment: 4 page
Elliptical orbits in the Bloch sphere
As is well known, when an SU(2) operation acts on a two-level system, its
Bloch vector rotates without change of magnitude. Considering a system composed
of two two-level systems, it is proven that for a class of nonlocal
interactions of the two subsystems including \sigma_i\otimes\sigma_j (with i,j
\in {x,y,z}) and the Heisenberg interaction, the geometric description of the
motion is particularly simple: each of the two Bloch vectors follows an
elliptical orbit within the Bloch sphere. The utility of this result is
demonstrated in two applications, the first of which bears on quantum control
via quantum interfaces. By employing nonunitary control operations, we extend
the idea of controllability to a set of points which are not necessarily
connected by unitary transformations. The second application shows how the
orbit of the coherence vector can be used to assess the entangling power of
Heisenberg exchange interaction.Comment: 9 pages, 4 figures, few corrections, J. Opt. B: Quantum Semiclass.
Opt. 7 (2005) S1-S
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