Analog control of open quantum systems under arbitrary decoherence. (arXiv:0909.1680v1 [quant-ph])

We derive and investigate a general non-Markovian equation for the
time-dependence of a Hamiltonian that maximizes the fidelity of a desired
quantum gate on any finite-dimensional quantum system in the presence of
arbitrary bath and noise sources. The method is illustrated for a single-qubit
gate implemented on a three-level system.

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Original source : http://arxiv.org/abs/0909.1680...

Anyonic Topological Quantum Computation and the Virtual Braid Group. (arXiv:0909.1672v1 [quant-ph])

We introduce a recoupling theory for virtual braided trees. This recoupling
theory can be utilized to incorporate swap gates into anyonic models of quantum
computation.

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Original source : http://arxiv.org/abs/0909.1672...

Entanglement of graph states up to 8 qubits. (arXiv:0909.1603v1 [quant-ph])

The entanglement of graph states up to eight qubits is calculated in the
regime of iteration calculation. The entanglement measures could be the
relative entropy of entanglement, the logarithmic robustness or the geometric
measure. All 146 local inequivalent graphs are classified as three categories:
the 2-colorable graphs, the non 2-colorable graphs with identical upper LOCC
entanglement bound and lower bipartite entanglement bound, the non 2-colorable
graphs with unequal bounds. The last may displays non-integer entanglement. The
precision of iteration calculation of the entanglement is less than $10^{-14}$.

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Original source : http://arxiv.org/abs/0909.1603...

Computation and Dynamics: Classical and Quantum. (arXiv:0909.1594v1 [quant-ph])

We discuss classical and quantum computations in terms of corresponding
Hamiltonian dynamics. This allows us to introduce quantum computations which
involve parallel processing of both: the data and programme instructions. Using
mixed quantum-classical dynamics we look for a full cost of computations on
quantum computers with classical terminals.

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Original source : http://arxiv.org/abs/0909.1594...

Real time plasma equilibrium reconstruction in a Tokamak. (arXiv:0909.1646v1 [math.NA])

The problem of equilibrium of a plasma in a Tokamak is a free boundary
problemdescribed by the Grad-Shafranov equation in axisymmetric configurations.
The right hand side of this equation is a non linear source, which represents
the toroidal component of the plasma current density. This paper deals with the
real time identification of this non linear source from experimental
measurements. The proposed method is based on a fixed point algorithm, a finite
element resolution, a reduced basis method and a least-square optimization
formulation.

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Original source : http://arxiv.org/abs/0909.1646...

RIOT: I/O-Efficient Numerical Computing without SQL. (arXiv:0909.1766v1 [cs.DB])

R is a numerical computing environment that is widely popular for statistical
data analysis. Like many such environments, R performs poorly for large
datasets whose sizes exceed that of physical memory. We present our vision of
RIOT (R with I/O Transparency), a system that makes R programs I/O-efficient in
a way transparent to the users. We describe our experience with RIOT-DB, an
initial prototype that uses a relational database system as a backend. Despite
the overhead and inadequacy of generic database systems in handling array data
and numerical computation, RIOT-DB significantly outperforms R in many
large-data scenarios, thanks to a suite of high-level, inter-operation
optimizations that integrate seamlessly into R. While many techniques in RIOT
are inspired by databases (and, for RIOT-DB, realized by a database system),
RIOT users are insulated from anything database related. Compared with previous
approaches that require users to learn new languages and rewrite their programs
to interface with a database, RIOT will, we believe, be easier to adopt by the
majority of the R users.

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Original source : http://arxiv.org/abs/0909.1766...

Proposed Quantum Computer Consists of Billions of Electron Spins

(PhysOrg.com) -- While researchers have already demonstrated the building blocks for few-bit quantum computers, scaling these systems up to large quantum computers remains a challenge. One of the biggest problems is developing physical systems that can reliably store thousands of qubits, and enabling bits and pairs to be addressed individually for gate operations.

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Original source : http://www.physorg.com/news171705608.html...