2,337 research outputs found
Operator quantum error correction for continuous dynamics
We study the conditions under which a subsystem code is correctable in the
presence of noise that results from continuous dynamics. We consider the case
of Markovian dynamics as well as the general case of Hamiltonian dynamics of
the system and the environment, and derive necessary and sufficient conditions
on the Lindbladian and system-environment Hamiltonian, respectively. For the
case when the encoded information is correctable during an entire time
interval, the conditions we obtain can be thought of as generalizations of the
previously derived conditions for decoherence-free subsystems to the case where
the subsystem is time dependent. As a special case, we consider conditions for
unitary correctability. In the case of Hamiltonian evolution, the conditions
for unitary correctability concern only the effect of the Hamiltonian on the
system, whereas the conditions for general correctability concern the entire
system-environment Hamiltonian. We also derive conditions on the Hamiltonian
which depend on the initial state of the environment, as well as conditions for
correctability at only a particular moment of time. We discuss possible
implications of our results for approximate quantum error correction.Comment: 11 pages, no figures, essentially the published version, includes a
new section on correctability at only a particular moment of tim
Fault tolerance for holonomic quantum computation
We review an approach to fault-tolerant holonomic quantum computation on
stabilizer codes. We explain its workings as based on adiabatic dragging of the
subsystem containing the logical information around suitable loops along which
the information remains protected.Comment: 16 pages, this is a chapter in the book "Quantum Error Correction",
edited by Daniel A. Lidar and Todd A. Brun, (Cambridge University Press,
2013), at
http://www.cambridge.org/us/academic/subjects/physics/quantum-physics-quantum-information-and-quantum-computation/quantum-error-correctio
A robust multivariable control for an electropneumatic system using backstepping design
International audienceDuring the last twenty years, the parallel development of pneumatic systems and control theory has lead to the implementation of modern control laws in pneumatic devices. This paper deals with the robust control problem of a pneumatic actuator subjected to mass flow leakage inside the servodistributor and load disturbances. The control strategy is based on backstepping design. For this, backstepping is presented in an informal setting. The nonlinear model of the electropneumatic system is presented. This one is transformed to be nonlinear affine model and a coordinate transformation is then related to make possible the implementation of the nonlinear controller. Control laws are developed using backstepping design to control position and pressure. The robustness visa -vis modeling errors and some unknown terms is proved. Finally, the experiment results are presented and discussed
Control design for energy saving
International audienceThis paper presents the interest of including control strategy into electropneumatic design. For this certain experimental results obtained in an electropneumatic process have been presented. Using two servo-distributors leads to a system with one degree of freedom. This opportunity is exploited for in two objectives. The first concerns positioning control and the second attempts to optimise energy efficiency. With this aim an energy optimisation algorithm has been presented. The chosen control algorithm issues from the flatness concept. KEY WORDS nonlinear control, flatness, energy saving, electropneumatic
Hybrid control for switching between position and force tracking
International audienceThis paper is the logical result of previous researches about advanced control in electropneumatic systems. After different works in feedback control of electropneumatic actuators in position tracking [1] or in force tracking [2], this study led about a method to switch between these two different focuses. This question is an important problem in many industrial systems, for example in the case of vehicle active suspension or for pneumatic or hydraulic pliers, fingers and spot welding, fatigue test. Indeed, some dangerous damages could occur when the aim is to move a load near a structure and to apply a force against this structure. The major difficulty is to know when and how to switch between the position control and the force control (this is here the notion of hybrid control). A classical occurrence is due to a static position error when the control algorithm switches from position feedback to force feedback. The result leads very often to an undesirable impact to the structure. KEYWORDS Force / position tracking, hybrid control, pneumatic
BAT - The Bayesian Analysis Toolkit
We describe the development of a new toolkit for data analysis. The analysis
package is based on Bayes' Theorem, and is realized with the use of Markov
Chain Monte Carlo. This gives access to the full posterior probability
distribution. Parameter estimation, limit setting and uncertainty propagation
are implemented in a straightforward manner. A goodness-of-fit criterion is
presented which is intuitive and of great practical use.Comment: 31 pages, 10 figure
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