51 research outputs found
An Algebra of Quantum Processes
We introduce an algebra qCCS of pure quantum processes in which no classical
data is involved, communications by moving quantum states physically are
allowed, and computations is modeled by super-operators. An operational
semantics of qCCS is presented in terms of (non-probabilistic) labeled
transition systems. Strong bisimulation between processes modeled in qCCS is
defined, and its fundamental algebraic properties are established, including
uniqueness of the solutions of recursive equations. To model sequential
computation in qCCS, a reduction relation between processes is defined. By
combining reduction relation and strong bisimulation we introduce the notion of
strong reduction-bisimulation, which is a device for observing interaction of
computation and communication in quantum systems. Finally, a notion of strong
approximate bisimulation (equivalently, strong bisimulation distance) and its
reduction counterpart are introduced. It is proved that both approximate
bisimilarity and approximate reduction-bisimilarity are preserved by various
constructors of quantum processes. This provides us with a formal tool for
observing robustness of quantum processes against inaccuracy in the
implementation of its elementary gates
Quantum Bisimilarity via Barbs and Contexts: Curbing the Power of Non-Deterministic Observers
Past years have seen the development of a few proposals for quantum
extensions of process calculi. The rationale is clear: with the development of
quantum communication protocols, there is a need to abstract and focus on the
basic features of quantum concurrent systems, like CCS has done for its
classical counterpart. So far, though, no accepted standard has emerged,
neither for the syntax nor for the behavioural semantics. Indeed, the various
proposals do not agree on what should be the observational properties of
quantum values, and as a matter of fact, the soundness of such properties has
never been validated against the prescriptions of quantum theory.
To this aim, we introduce a new calculus, Linear Quantum CCS, and investigate
the features of behavioural equivalences based on barbs and contexts. Our
calculus can be thought of as an asynchronous, linear version of qCCS (based on
value-passing CCS). Linearity ensures that each qubit is sent exactly once,
precisely specifying which qubits of a process interact with the context.
We exploit contexts to examine how bisimilarities relate to quantum theory.
We show that the observational power of general contexts is incompatible with
quantum theory: roughly, they can perform non-deterministic moves depending on
quantum values without measuring (hence perturbing) them.
Therefore, we refine the operational semantics in order to prevent contexts
from performing unfeasible non-deterministic choices. This induces a coarser
bisimilarity that better fits the quantum setting: (i) it lifts the
indistinguishability of quantum states to the distributions of processes and,
despite the additional constraints, (ii) it preserves the expressivity of
non-deterministic choices based on classical information. To the best of our
knowledge, our semantics is the first one that satisfies the two properties
above.Comment: This is the extended version of the POPL2024 paper "Quantum
Bisimilarity via Barbs and Contexts: Curbing the Power of Non-Deterministic
Observers
The Way We Were: Structural Operational Semantics Research in Perspective
This position paper on the (meta-)theory of Structural Operational Semantic
(SOS) is motivated by the following two questions: (1) Is the (meta-)theory of
SOS dying out as a research field? (2) If so, is it possible to rejuvenate this
field with a redefined purpose?
In this article, we will consider possible answers to those questions by
first analysing the history of the EXPRESS/SOS workshops and the data
concerning the authors and the presentations featured in the editions of those
workshops as well as their subject matters.
The results of our quantitative and qualitative analyses all indicate a
diminishing interest in the theory of SOS as a field of research. Even though
`all good things must come to an end', we strive to finish this position paper
on an upbeat note by addressing our second motivating question with some
optimism. To this end, we use our personal reflections and an analysis of
recent trends in two of the flagship conferences in the field of Programming
Languages (namely POPL and PDLI) to draw some conclusions on possible future
directions that may rejuvenate research on the (meta-)theory of SOS. We hope
that our musings will entice members of the research community to breathe new
life into a field of research that has been kind to three of the authors of
this article.Comment: In Proceedings EXPRESS/SOS2023, arXiv:2309.0578
Processes, Systems \& Tests: Defining Contextual Equivalences
In this position paper, we would like to offer and defend a new template to
study equivalences between programs -- in the particular framework of process
algebras for concurrent computation.We believe that our layered model of
development will clarify the distinction that is too often left implicit
between the tasks and duties of the programmer and of the tester. It will also
enlighten pre-existing issues that have been running across process algebras as
diverse as the calculus of communicating systems, the -calculus -- also
in its distributed version -- or mobile ambients.Our distinction starts by
subdividing the notion of process itself in three conceptually separated
entities, that we call \emph{Processes}, \emph{Systems} and \emph{Tests}.While
the role of what can be observed and the subtleties in the definitions of
congruences have been intensively studied, the fact that \emph{not every
process can be tested}, and that \emph{the tester should have access to a
different set of tools than the programmer} is curiously left out, or at least
not often formally discussed.We argue that this blind spot comes from the
under-specification of contexts -- environments in which comparisons takes
place -- that play multiple distinct roles but supposedly always \enquote{stay
the same}.We illustrate our statement with a simple Java example, the
\enquote{usual} concurrent languages, but also back it up with
-calculus and existing implementations of concurrent languages as
well
Quantum computation, quantum theory and AI
The main purpose of this paper is to examine some (potential) applications of quantum computation in AI and to review the interplay between quantum theory and AI. For the readers who are not familiar with quantum computation, a brief introduction to it is provided, and a famous but simple quantum algorithm is introduced so that they can appreciate the power of quantum computation. Also, a (quite personal) survey of quantum computation is presented in order to give the readers a (unbalanced) panorama of the field. The author hopes that this paper will be a useful map for AI researchers who are going to explore further and deeper connections between AI and quantum computation as well as quantum theory although some parts of the map are very rough and other parts are empty, and waiting for the readers to fill in. © 2009 Elsevier B.V. All rights reserved
Model checking quantum protocols
This thesis describes model checking techniques for protocols arising in quantum information
theory and quantum cryptography. We discuss the theory and implementation of a practical
model checker, QMC, for quantum protocols. In our framework, we assume that the quantum
operations performed in a protocol are restricted to those within the stabilizer formalism; while
this particular set of operations is not universal for quantum computation, it allows us to develop
models of several useful protocols as well as of systems involving both classical and quantum
information processing. We detail the syntax, semantics and type system of QMC’s modelling
language, the logic QCTL which is used for verification, and the verification algorithms that have
been implemented in the tool. We demonstrate our techniques with applications to a number of
case studies
Tools and Algorithms for the Construction and Analysis of Systems
This open access two-volume set constitutes the proceedings of the 26th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2020, which took place in Dublin, Ireland, in April 2020, and was held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The total of 60 regular papers presented in these volumes was carefully reviewed and selected from 155 submissions. The papers are organized in topical sections as follows: Part I: Program verification; SAT and SMT; Timed and Dynamical Systems; Verifying Concurrent Systems; Probabilistic Systems; Model Checking and Reachability; and Timed and Probabilistic Systems. Part II: Bisimulation; Verification and Efficiency; Logic and Proof; Tools and Case Studies; Games and Automata; and SV-COMP 2020
Foundations of Software Science and Computation Structures
This open access book constitutes the proceedings of the 22nd International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2019, which took place in Prague, Czech Republic, in April 2019, held as part of the European Joint Conference on Theory and Practice of Software, ETAPS 2019. The 29 papers presented in this volume were carefully reviewed and selected from 85 submissions. They deal with foundational research with a clear significance for software science
Programming Languages and Systems
This open access book constitutes the proceedings of the 30th European Symposium on Programming, ESOP 2021, which was held during March 27 until April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The 24 papers included in this volume were carefully reviewed and selected from 79 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems
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