199 research outputs found
Observability and Decentralized Control of Fuzzy Discrete Event Systems
Fuzzy discrete event systems as a generalization of (crisp) discrete event
systems have been introduced in order that it is possible to effectively
represent uncertainty, imprecision, and vagueness arising from the dynamic of
systems. A fuzzy discrete event system has been modelled by a fuzzy automaton;
its behavior is described in terms of the fuzzy language generated by the
automaton. In this paper, we are concerned with the supervisory control problem
for fuzzy discrete event systems with partial observation. Observability,
normality, and co-observability of crisp languages are extended to fuzzy
languages. It is shown that the observability, together with controllability,
of the desired fuzzy language is a necessary and sufficient condition for the
existence of a partially observable fuzzy supervisor. When a decentralized
solution is desired, it is proved that there exist local fuzzy supervisors if
and only if the fuzzy language to be synthesized is controllable and
co-observable. Moreover, the infimal controllable and observable fuzzy
superlanguage, and the supremal controllable and normal fuzzy sublanguage are
also discussed. Simple examples are provided to illustrate the theoretical
development.Comment: 14 pages, 1 figure. to be published in the IEEE Transactions on Fuzzy
System
A modified quantum adiabatic evolution for the Deutsch-Jozsa problem
Deutsch-Jozsa algorithm has been implemented via a quantum adiabatic
evolution by S. Das et al. [Phys. Rev. A 65, 062310 (2002)]. This adiabatic
algorithm gives rise to a quadratic speed up over classical algorithms. We show
that a modified version of the adiabatic evolution in that paper can improve
the performance to constant time.Comment: 2 pages, no figur
(Un)decidable Problems about Reachability of Quantum Systems
We study the reachability problem of a quantum system modelled by a quantum
automaton. The reachable sets are chosen to be boolean combinations of (closed)
subspaces of the state space of the quantum system. Four different reachability
properties are considered: eventually reachable, globally reachable, ultimately
forever reachable, and infinitely often reachable. The main result of this
paper is that all of the four reachability properties are undecidable in
general; however, the last three become decidable if the reachable sets are
boolean combinations without negation
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