10,241 research outputs found
Synthesis of linear quantum stochastic systems via quantum feedback networks
Recent theoretical and experimental investigations of coherent feedback
control, the feedback control of a quantum system with another quantum system,
has raised the important problem of how to synthesize a class of quantum
systems, called the class of linear quantum stochastic systems, from basic
quantum optical components and devices in a systematic way. The synthesis
theory sought in this case can be naturally viewed as a quantum analogue of
linear electrical network synthesis theory and as such has potential for
applications beyond the realization of coherent feedback controllers. In
earlier work, Nurdin, James and Doherty have established that an arbitrary
linear quantum stochastic system can be realized as a cascade connection of
simpler one degree of freedom quantum harmonic oscillators, together with a
direct interaction Hamiltonian which is bilinear in the canonical operators of
the oscillators. However, from an experimental perspective and based on current
methods and technologies, direct interaction Hamiltonians are challenging to
implement for systems with more than just a few degrees of freedom. In order to
facilitate more tractable physical realizations of these systems, this paper
develops a new synthesis algorithm for linear quantum stochastic systems that
relies solely on field-mediated interactions, including in implementation of
the direct interaction Hamiltonian. Explicit synthesis examples are provided to
illustrate the realization of two degrees of freedom linear quantum stochastic
systems using the new algorithm.Comment: 21 pages, 6 figure
Network Synthesis of Linear Dynamical Quantum Stochastic Systems
The purpose of this paper is to develop a synthesis theory for linear
dynamical quantum stochastic systems that are encountered in linear quantum
optics and in phenomenological models of linear quantum circuits. In
particular, such a theory will enable the systematic realization of
coherent/fully quantum linear stochastic controllers for quantum control,
amongst other potential applications. We show how general linear dynamical
quantum stochastic systems can be constructed by assembling an appropriate
interconnection of one degree of freedom open quantum harmonic oscillators and,
in the quantum optics setting, discuss how such a network of oscillators can be
approximately synthesized or implemented in a systematic way from some linear
and non-linear quantum optical elements. An example is also provided to
illustrate the theory.Comment: Revised and corrected version, published in SIAM Journal on Control
and Optimization, 200
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
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
The SLH framework for modeling quantum input-output networks
Many emerging quantum technologies demand precise engineering and control
over networks consisting of quantum mechanical degrees of freedom connected by
propagating electromagnetic fields, or quantum input-output networks. Here we
review recent progress in theory and experiment related to such quantum
input-output networks, with a focus on the SLH framework, a powerful modeling
framework for networked quantum systems that is naturally endowed with
properties such as modularity and hierarchy. We begin by explaining the
physical approximations required to represent any individual node of a network,
eg. atoms in cavity or a mechanical oscillator, and its coupling to quantum
fields by an operator triple . Then we explain how these nodes can be
composed into a network with arbitrary connectivity, including coherent
feedback channels, using algebraic rules, and how to derive the dynamics of
network components and output fields. The second part of the review discusses
several extensions to the basic SLH framework that expand its modeling
capabilities, and the prospects for modeling integrated implementations of
quantum input-output networks. In addition to summarizing major results and
recent literature, we discuss the potential applications and limitations of the
SLH framework and quantum input-output networks, with the intention of
providing context to a reader unfamiliar with the field.Comment: 60 pages, 14 figures. We are still interested in receiving
correction
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