33,178 research outputs found
State Transfer and Spin Measurement
We present a Hamiltonian that can be used for amplifying the signal from a
quantum state, enabling the measurement of a macroscopic observable to
determine the state of a single spin. We prove a general mapping between this
Hamiltonian and an exchange Hamiltonian for arbitrary coupling strengths and
local magnetic fields. This facilitates the use of existing schemes for perfect
state transfer to give perfect amplification. We further prove a link between
the evolution of this fixed Hamiltonian and classical Cellular Automata,
thereby unifying previous approaches to this amplification task.
Finally, we show how to use the new Hamiltonian for perfect state transfer in
the, to date, unique scenario where total spin is not conserved during the
evolution, and demonstrate that this yields a significantly different response
in the presence of decoherence.Comment: 4 pages, 2 figure
Resonance absolute quantum reflection at selected energies
The possibility of the resonance reflection (100 % at maximum) is revealed.
The corresponding exactly solvable models with the controllable numbers of
resonances, their positions and widths are presented.Comment: 5 pages, 2 figure
Natural three-qubit interactions in one-way quantum computing
We address the effects of natural three-qubit interactions on the
computational power of one-way quantum computation (\QC). A benefit of using
more sophisticated entanglement structures is the ability to construct compact
and economic simulations of quantum algorithms with limited resources. We show
that the features of our study are embodied by suitably prepared optical
lattices, where effective three-spin interactions have been theoretically
demonstrated. We use this to provide a compact construction for the Toffoli
gate. Information flow and two-qubit interactions are also outlined, together
with a brief analysis of relevant sources of imperfection.Comment: 4 pages, 3 figures, RevTeX
Evaluation of a manufacturing task support system using the Task Technology Fit Model
This paper presents an exploratory study of a Task Support System (TSS) supporting manufacturing task operations. The study investigated the degree to which a TSS, in use in a company, actually supports the task of the shop floor personnel. The approach has been to adopt the Task-Technology Fit (TTF) instrument to measure
the degree of fitness between the TSS and the associated task. The analysis gives an indication of the state of the TSS and the potential improvements that can be made. The study also shows that the instrument can be used as a foundation for the development of a hypermedia TSS and a benchmarking tool for a TSS
Self-energy flows in the two-dimensional repulsive Hubbard model
We study the two-dimensional repulsive Hubbard model by functional RG
methods, using our recently proposed channel decomposition of the interaction
vertex. The main technical advance of this work is that we calculate the full
Matsubara frequency dependence of the self-energy and the interaction vertex in
the whole frequency range without simplifying assumptions on its functional
form, and that the effects of the self-energy are fully taken into account in
the equations for the flow of the two-body vertex function. At Van Hove
filling, we find that the Fermi surface deformations remain small at fixed
particle density and have a minor impact on the structure of the interaction
vertex. The frequency dependence of the self-energy, however, turns out to be
important, especially at a transition from ferromagnetism to d-wave
superconductivity. We determine non-Fermi-liquid exponents at this transition
point.Comment: 48 pages, 18 figure
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