4,516 research outputs found
Structuring Multilevel Discrete-Event Systems With Dependence Structure Matrices
Despite the correct-by-construction property, one of the major drawbacks of supervisory control synthesis is state-space explosion. Several approaches have been proposed to overcome this computational difficulty, such as modular, hierarchical, decentralized, and multilevel supervisory control synthesis. Unfortunately, the modeler needs to provide additional information about the system's structure or controller's structure as input for most of these nonmonolithic synthesis procedures. Multilevel synthesis assumes that the system is provided in a tree-structured format, which may resemble a system decomposition. In this paper, we present a systematic approach to transform a set of plant models and a set of requirement models provided as extended finite automata into a tree-structured multilevel discrete-event system to which multilevel supervisory control synthesis can be applied. By analyzing the dependencies between the plants and the requirements using dependence structure matrix techniques, a multilevel clustering can be calculated. With the modeling framework of extended finite automata, plant models and requirements depend on each other when they share events or variables. We report on experimental results of applying the algorithm's implementation on several models available in the literature to assess the applicability of the proposed method. The benefit of multilevel synthesis based on the calculated clustering is significant for most large-scale systems
Magic-State Functional Units: Mapping and Scheduling Multi-Level Distillation Circuits for Fault-Tolerant Quantum Architectures
Quantum computers have recently made great strides and are on a long-term
path towards useful fault-tolerant computation. A dominant overhead in
fault-tolerant quantum computation is the production of high-fidelity encoded
qubits, called magic states, which enable reliable error-corrected computation.
We present the first detailed designs of hardware functional units that
implement space-time optimized magic-state factories for surface code
error-corrected machines. Interactions among distant qubits require surface
code braids (physical pathways on chip) which must be routed. Magic-state
factories are circuits comprised of a complex set of braids that is more
difficult to route than quantum circuits considered in previous work [1]. This
paper explores the impact of scheduling techniques, such as gate reordering and
qubit renaming, and we propose two novel mapping techniques: braid repulsion
and dipole moment braid rotation. We combine these techniques with graph
partitioning and community detection algorithms, and further introduce a
stitching algorithm for mapping subgraphs onto a physical machine. Our results
show a factor of 5.64 reduction in space-time volume compared to the best-known
previous designs for magic-state factories.Comment: 13 pages, 10 figure
Model Properties for Efficient Synthesis of Nonblocking Modular Supervisors
Supervisory control theory provides means to synthesize supervisors for
systems with discrete-event behavior from models of the uncontrolled plant and
of the control requirements. The applicability of supervisory control theory
often fails due to a lack of scalability of the algorithms. We propose a format
for the requirements and a method to ensure that the crucial properties of
controllability and nonblockingness directly hold, thus avoiding the most
computationally expensive parts of synthesis. The method consists of creating a
control problem dependency graph and verifying whether it is acyclic. Vertices
of the graph are modular plant components, and edges are derived from the
requirements. In case of a cyclic graph, potential blocking issues can be
localized, so that the original control problem can be reduced to only
synthesizing supervisors for smaller partial control problems. The strength of
the method is illustrated on two case studies: a production line and a roadway
tunnel.Comment: Submitted to Journal of Control Engineering Practice, revision
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