2,540 research outputs found
Direct and Indirect Couplings in Coherent Feedback Control of Linear Quantum Systems
The purpose of this paper is to study and design direct and indirect
couplings for use in coherent feedback control of a class of linear quantum
stochastic systems. A general physical model for a nominal linear quantum
system coupled directly and indirectly to external systems is presented.
Fundamental properties of stability, dissipation, passivity, and gain for this
class of linear quantum models are presented and characterized using complex
Lyapunov equations and linear matrix inequalities (LMIs). Coherent
and LQG synthesis methods are extended to accommodate direct couplings using
multistep optimization. Examples are given to illustrate the results.Comment: 33 pages, 7 figures; accepted for publication in IEEE Transactions on
Automatic Control, October 201
Selective linear or quadratic optomechanical coupling via measurement
The ability to engineer both linear and non-linear coupling with a mechanical
resonator is an important goal for the preparation and investigation of
macroscopic mechanical quantum behavior. In this work, a measurement based
scheme is presented where linear or square mechanical displacement coupling can
be achieved using the optomechanical interaction linearly proportional to the
mechanical position. The resulting square displacement measurement strength is
compared to that attainable in the dispersive case using the direct interaction
to the mechanical displacement squared. An experimental protocol and parameter
set are discussed for the generation and observation of non-Gaussian states of
motion of the mechanical element.Comment: 7 pages, 2 figures, (accepted in Physical Review X
Quantum Feedback Networks and Control: A Brief Survey
The purpose of this paper is to provide a brief review of some recent
developments in quantum feedback networks and control. A quantum feedback
network (QFN) is an interconnected system consisting of open quantum systems
linked by free fields and/or direct physical couplings. Basic network
constructs, including series connections as well as feedback loops, are
discussed. The quantum feedback network theory provides a natural framework for
analysis and design. Basic properties such as dissipation, stability, passivity
and gain of open quantum systems are discussed. Control system design is also
discussed, primarily in the context of open linear quantum stochastic systems.
The issue of physical realizability is discussed, and explicit criteria for
stability, positive real lemma, and bounded real lemma are presented. Finally
for linear quantum systems, coherent and LQG control are described.Comment: 29 pages, 11 figures. A new reference has been adde
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