News

Jan 13 15:00 ₂₀₂₃

Abstract: The advent of quantum computers capable of solving problems that are intractable on classical computers has motivated the development of new programming languages and tools for quantum computing. However, the current state of the art in quantum programming is still in its infancy.

In this thesis, we present a series of novel approaches to different aspects of the quantum compilation process based on the ZX calculus. Read more...

Jan 9 14:00 ₂₀₂₃

Abstract: In this thesis, we are interested in the development of a Curry-Howard correspondence for quantum computing, allowing to represent quantum types and quantum control-flow. In the standard model of Quantum Computation, a classical computer is linked to a quantum coprocessor. The classical computer can then send instructions to allocate, update, or read quantum registers. The programs executed by the coprocessor are represented by a quantum circuit: a sequence of instructions that applies unitary operations to the input quantum bits. Read more...

Dec 14 14:00 ₂₀₂₂

Abstract: Multicore OCaml extends OCaml with support for shared-memory concurrency. It is equipped with a weak memory model, for which an operational semantics has been published. This begs the question: what reasoning rules can one rely upon while writing or verifying Multicore OCaml code?

To answer it, we instantiate Iris, a modern descendant of Concurrent Separation Logic, for Multicore OCaml. This yields a low-level program logic whose reasoning rules expose the details of the memory model. On top of it, we build a higher-level logic, Cosmo, which trades off some expressive power in return for a simple set of reasoning rules that allow accessing non-atomic locations in a data-race-free manner, exploiting the sequentially-consistent behavior of atomic locations, and exploiting the release/acquire behavior of atomic locations. Cosmo allows both low-level reasoning, where the details of the Multicore OCaml memory model are apparent, and high-level reasoning, which is independent of this memory model.

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Dec 12 14:00 ₂₀₂₂

Abstract: Distributed systems involve processes that run independently and communicate asynchronously. While they capture a wide range of use cases and are hence, ubiquitous in our world, it is also particularly difficult to ensure their correctness.

In this thesis, we model such systems using mathematical and logical formulation, and try to verify them algorithmically. In particular, we focus on FIFO (First-In First-Out) machines, with one or more finite-state machines communicating via unbounded reliable FIFO buffers. Read more...

Dec 13 9:00 ₂₀₂₂

Abstract: The most standard model checking approaches are limited to verifying concrete specifications, such as “can we reach a configuration with more than 10 time units elapsing ?”. Nevertheless, for certain computer programs, like embedded systems, the constraints depend on the environment. Thus arises the need for parametric specifications, such as “can we reach a configuration with more than p time units elapsing ?” where p is a parameter which takes values in the non-negative integers.

In this thesis, we study parametric pushdown, counter and timed automata and extensions thereof. In addition to expressing concrete constraints (on the stack, on the counter or on clocks), these can employ parametric constraints. The reachability problem for a parametric automaton asks for the existence of an assignment of the parameters such that there exists an accepting run in the underlying concrete automaton. In addition to the reachability problem, we consider parametric parity games, two player games where players alternate choosing assignments for each parameters, then alternate moving a token along the configurations of the concrete automaton resulting from their choice of parameter assignment. We consider the problem of deciding which player has a winning strategy.

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Mathilde Boltenhagen received the Best Process Mining PhD Dissertation Award 2022 during the Fourth International Conference on Process Mining (ICPM 2022) for her thesis entitled "Process Instance Clustering based on Conformance Checking Artefacts".

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Un article sur Evelyne Contejean vient de paraitre dans la rubrique Portraits de chercheurs des Actualités de l'Université Paris-Saclay.

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Un article sur Thomas Nowak vient de paraitre sur le site de l'ENS Paris-Saclay.

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Sep 27 17:00 ₂₀₂₂

Abstract: Safe programming as well as most proof systems rely on typing. The more a type system is expressive, the more these types can be used to encode invariants which are therefore verified mechanically through type checking procedures. Predicate subtyping extends simple type theory by allowing terms to be defined by predicates. A predicate subtype { x : A | P(x) } is inhabited by terms t of type A for which P(t) holds. This extension provides a rich and intuitive but undecidable type system.

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Pierre Vandenhove est lauréat d'un accessit au Prix « Doctorants » du plateau de Saclay dans la domaine STIC - Sciences et Technologies de l'Information et la Communication.

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