376 research outputs found
On the generalization of linear least mean squares estimation to quantum systems with non-commutative outputs
The purpose of this paper is to study the problem of generalizing the
Belavkin-Kalman filter to the case where the classical measurement signal is
replaced by a fully quantum non-commutative output signal. We formulate a least
mean squares estimation problem that involves a non-commutative system as the
filter processing the non-commutative output signal. We solve this estimation
problem within the framework of non-commutative probability. Also, we find the
necessary and sufficient conditions which make these non-commutative estimators
physically realizable. These conditions are restrictive in practice.Comment: 31 page
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
A Systems Theory Approach to the Synthesis of Minimum Noise Phase-Insensitive Quantum Amplifiers
We present a systems theory approach to the proof of a result bounding the
required level of added quantum noise in a phase-insensitive quantum amplifier.
We also present a synthesis procedure for constructing a quantum optical
phase-insensitive quantum amplifier which adds the minimum level of quantum
noise and achieves a required gain and bandwidth. This synthesis procedure is
based on a singularly perturbed quantum system and leads to an amplifier
involving two squeezers and two beamsplitters.Comment: To appear in the Proceedings of the 2018 European Control Conferenc
A Direct Coupling Coherent Quantum Observer for a Single Qubit Finite Level Quantum System
This paper considers the problem of constructing a direct coupling quantum
observer for a single qubit finite level quantum system plant. The proposed
observer is a single mode linear quantum system which is shown to be able to
estimate one of the plant variables in a time averaged sense. A numerical
example and simulations are included to illustrate the properties of the
observer.Comment: A preliminary version of this paper has been accepted to appear in
the 2014 Australian Control Conferenc
Coherent-Classical Estimation for Quantum Linear Systems
This paper introduces a problem of coherent-classical estimation for a class
of linear quantum systems. In this problem, the estimator is a mixed
quantum-classical system which produces a classical estimate of a system
variable. The coherent-classical estimator may also involve coherent feedback.
An example involving optical squeezers is given to illustrate the efficacy of
this idea.Comment: A version of this paper will appear in the Proceedings of the 2013
Australian Control Conferenc
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