222 research outputs found
the EU's policy on genetic resources in the CBD / WIPO / TRIPS nexus
The present paper aims at an analysis of the coherence of the European Union’s
policy output in the field of Access and Benefit-Sharing, in the nexus between
the Convention on Biological Diversity, the World Intellectual Property
Organization and the Agreement on Trade-related Aspects of Intellectual
Property Rights. As some preliminary data suggests, during 2006, the EU
approach to ABS was fundamentally reorganized. The paper sets out to test
whether such a reorganization can be found at the level of policy coherence.
Statistical analysis suggests, that with one of two measures for policy
coherence, a rupture around 2006 can be observed.First rough draf
Quantum Multiobservable Control
We present deterministic algorithms for the simultaneous control of an
arbitrary number of quantum observables. Unlike optimal control approaches
based on cost function optimization, quantum multiobservable tracking control
(MOTC) is capable of tracking predetermined homotopic trajectories to target
expectation values in the space of multiobservables. The convergence of these
algorithms is facilitated by the favorable critical topology of quantum control
landscapes. Fundamental properties of quantum multiobservable control
landscapes that underlie the efficiency of MOTC, including the multiobservable
controllability Gramian, are introduced. The effects of multiple control
objectives on the structure and complexity of optimal fields are examined. With
minor modifications, the techniques described herein can be applied to general
quantum multiobjective control problems.Comment: To appear in Physical Review
Encoding a qubit into multilevel subspaces
We present a formalism for encoding the logical basis of a qubit into
subspaces of multiple physical levels. The need for this multilevel encoding
arises naturally in situations where the speed of quantum operations exceeds
the limits imposed by the addressability of individual energy levels of the
qubit physical system. A basic feature of the multilevel encoding formalism is
the logical equivalence of different physical states and correspondingly, of
different physical transformations. This logical equivalence is a source of a
significant flexibility in designing logical operations, while the multilevel
structure inherently accommodates fast and intense broadband controls thereby
facilitating faster quantum operations. Another important practical advantage
of multilevel encoding is the ability to maintain full quantum-computational
fidelity in the presence of mixing and decoherence within encoding subspaces.
The formalism is developed in detail for single-qubit operations and
generalized for multiple qubits. As an illustrative example, we perform a
simulation of closed-loop optimal control of single-qubit operations for a
model multilevel system, and subsequently apply these operations at finite
temperatures to investigate the effect of decoherence on operational fidelity.Comment: IOPart LaTeX, 2 figures, 31 pages; addition of a numerical simulatio
Beable trajectories for revealing quantum control mechanisms
The dynamics induced while controlling quantum systems by optimally shaped
laser pulses have often been difficult to understand in detail. A method is
presented for quantifying the importance of specific sequences of quantum
transitions involved in the control process. The method is based on a
``beable'' formulation of quantum mechanics due to John Bell that rigorously
maps the quantum evolution onto an ensemble of stochastic trajectories over a
classical state space. Detailed mechanism identification is illustrated with a
model 7-level system. A general procedure is presented to extract mechanism
information directly from closed-loop control experiments. Application to
simulated experimental data for the model system proves robust with up to 25%
noise.Comment: Latex, 20 pages, 13 figure
Unified analysis of terminal-time control in classical and quantum systems
Many phenomena in physics, chemistry, and biology involve seeking an optimal
control to maximize an objective for a classical or quantum system which is
open and interacting with its environment. The complexity of finding an optimal
control for maximizing an objective is strongly affected by the possible
existence of sub-optimal maxima. Within a unified framework under specified
conditions, control objectives for maximizing at a terminal time physical
observables of open classical and quantum systems are shown to be inherently
free of sub-optimal maxima. This attractive feature is of central importance
for enabling the discovery of controls in a seamless fashion in a wide range of
phenomena transcending the quantum and classical regimes.Comment: 10 page
Loading a Bose-Einstein Condensate onto an Optical Lattice: an Application of Optimal Control Theory to The Non Linear Schr\"odinger Equation
Using a set of general methods developed by Krotov [A. I. Konnov and V. A.
Krotov, Automation and Remote Control, {\bf 60}, 1427 (1999)], we extend the
capabilities of Optimal Control Theory to the Nonlinear Schr\"odinger Equation
(NLSE). The paper begins with a general review of the Krotov approach to
optimization. Although the linearized version of the method is sufficient for
the linear Schr\"odinger equation, the full flexibility of the general method
is required for treatment of the nonlinear Schr\"odinger equation. Formal
equations for the optimization of the NLSE, as well as a concrete algorithm are
presented. As an illustration, we consider a Bose-Einstein condensate initially
at rest in a harmonic trap. A phase develops across the BEC when an optical
lattice potential is turned on. The goal is to counter this effect and keep the
phase flat by adjusting the trap strength. The problem is formulated in the
language of Optimal Control Theory (OCT) and solved using the above
methodology. To our knowledge, this is the first rigorous application of OCT to
the Nonlinear Schr\"odinger equation, a capability that is bound to have
numerous other applications.Comment: 11 pages, 4 figures, A reference added, Some typos correcte
Extracting molecular Hamiltonian structure from time-dependent fluorescence intensity data
We propose a formalism for extracting molecular Hamiltonian structure from
inversion of time-dependent fluorescence intensity data. The proposed method
requires a minimum of \emph{a priori} knowledge about the system and allows for
extracting a complete set of information about the Hamiltonian for a pair of
molecular electronic surfaces.Comment: 7pages, no figures, LaTeX2
Volume Fractions of the Kinematic "Near-Critical" Sets of the Quantum Ensemble Control Landscape
An estimate is derived for the volume fraction of a subset in the neighborhood
of the critical set
of the kinematic quantum ensemble control landscape J(U) = Tr(U\rho U' O),
where represents the unitary time evolution operator, {\rho} is the initial
density matrix of the ensemble, and O is an observable operator. This estimate
is based on the Hilbert-Schmidt geometry for the unitary group and a
first-order approximation of . An upper bound on these
near-critical volumes is conjectured and supported by numerical simulation,
leading to an asymptotic analysis as the dimension of the quantum system
rises in which the volume fractions of these "near-critical" sets decrease to
zero as increases. This result helps explain the apparent lack of influence
exerted by the many saddles of over the gradient flow.Comment: 27 pages, 1 figur
Learning from learning algorithms: application to attosecond dynamics of high-harmonic generation
Includes bibliographical references (pages 043404-5).Using experiment and modeling, we show that the data set generated when a learning algorithm is used to optimize a quantum system can help to uncover the physics behind the process being optimized. In particular, by optimizing the process of high-harmonic generation using shaped light pulses, we generate a large data set and analyze its statistical behavior. This behavior is then compared with theoretical predictions, verifying our understanding of the attosecond dynamics of high-harmonic generation and uncovering an anomalous region of parameter space
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