18,380 research outputs found
Multipartite entanglement and few-body Hamiltonians
We investigate the possibility to obtain higly multipartite-entangled states
as nondegenerate eigenstates of Hamiltonians that involve only short-range and
few-body interactions. We study small-size systems (with a number of qubits
ranging from three to five) and search for Hamiltonians with a Maximally
Multipartite Entangled State (MMES) as a nondegenerate eigenstate. We then find
conditions, including bounds on the number of coupled qubits, to build a
Hamiltonian with a Greenberger-Horne-Zeilinger (GHZ) state as a nondegenerate
eigenstate. We finally comment on possible applications.Comment: 15 pages, 3 figures. Proceedings of IQIS 2013 to appear on IJQ
A Spinning Mirror for Fast Angular Scans of EBW Emission for Magnetic Pitch Profile Measurement
A tilted spinning mirror rapidly steers the line of sight of the electron
Bernstein wave (EBW) emission radiometer at the Mega Amp Spherical Tokamak
(MAST). In order to resist high mechanical stresses at rotation speeds of up to
12,000 rpm and to avoid eddy current induced magnetic braking, the mirror
consists of a glass-reinforced nylon substrate of a special self-balanced
design, coated with a reflecting layer. By completing an angular scan every
2.5-10ms, it allows one to characterize with good time resolution the
Bernstein-extraordinary-ordinary mode-conversion efficiency as a function of
the view angles. Angular maps of conversion efficiency are directly related to
the magnetic pitch angle at the cutoff layer for the ordinary mode. Hence,
measurements at various frequencies provide the safety factor profile at the
plasma edge. Initial measurements and indications of the feasibility of the
diagnostic are presented. Moreover, angular scans indicate the best launch
conditions for EBW heating.Comment: 4 pages, 7 figures. Presented at High Temperature Plasma Diagnostics
(HTPD) Conference. Accepted on June 15, 2010 for publication on
Rev.Sci.Instru
Open boundary Quantum Knizhnik-Zamolodchikov equation and the weighted enumeration of Plane Partitions with symmetries
We propose new conjectures relating sum rules for the polynomial solution of
the qKZ equation with open (reflecting) boundaries as a function of the quantum
parameter and the -enumeration of Plane Partitions with specific
symmetries, with . We also find a conjectural relation \`a la
Razumov-Stroganov between the limit of the qKZ solution and refined
numbers of Totally Symmetric Self Complementary Plane Partitions.Comment: 27 pages, uses lanlmac, epsf and hyperbasics, minor revision
Correlation Plenoptic Imaging With Entangled Photons
Plenoptic imaging is a novel optical technique for three-dimensional imaging
in a single shot. It is enabled by the simultaneous measurement of both the
location and the propagation direction of light in a given scene. In the
standard approach, the maximum spatial and angular resolutions are inversely
proportional, and so are the resolution and the maximum achievable depth of
focus of the 3D image. We have recently proposed a method to overcome such
fundamental limits by combining plenoptic imaging with an intriguing
correlation remote-imaging technique: ghost imaging. Here, we theoretically
demonstrate that correlation plenoptic imaging can be effectively achieved by
exploiting the position-momentum entanglement characterizing spontaneous
parametric down-conversion (SPDC) photon pairs. As a proof-of-principle
demonstration, we shall show that correlation plenoptic imaging with entangled
photons may enable the refocusing of an out-of-focus image at the same depth of
focus of a standard plenoptic device, but without sacrificing
diffraction-limited image resolution.Comment: 12 pages, 5 figure
Quantum Knizhnik-Zamolodchikov equation: reflecting boundary conditions and combinatorics
We consider the level 1 solution of quantum Knizhnik-Zamolodchikov equation
with reflecting boundary conditions which is relevant to the Temperley--Lieb
model of loops on a strip. By use of integral formulae we prove conjectures
relating it to the weighted enumeration of Cyclically Symmetric Transpose
Complement Plane Partitions and related combinatorial objects
Sum rules for the ground states of the O(1) loop model on a cylinder and the XXZ spin chain
The sums of components of the ground states of the O(1) loop model on a
cylinder or of the XXZ quantum spin chain at Delta=-1/2 (of size L) are
expressed in terms of combinatorial numbers. The methods include the
introduction of spectral parameters and the use of integrability, a mapping
from size L to L+1, and knot-theoretic skein relations.Comment: final version to be publishe
Quantum Typicality and Initial Conditions
If the state of a quantum system is sampled out of a suitable ensemble, the
measurement of some observables will yield (almost) always the same result.
This leads us to the notion of quantum typicality: for some quantities the
initial conditions are immaterial. We discuss this problem in the framework of
Bose-Einstein condensates.Comment: 8 page
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