Cari amici, Spring greetings! I'd like to invite everyone to the "first" CQI seminar of the semester at 14:30 in D5.01, or online at https://meet.jit.si/cqi -demon-M6QW9V7YY (actually we've had several seminars already, just in the framework of the Information and Physics student seminar). In this talk Charles Bédard will tell us about ZX calculus, a diagrammatic language for reasoning about quantum circuits in the style of Penrose's tensor notation. Title and abstract below. Hoping to see everyone there, Will Schober Title: On Tensor Networks and ZX Calculus, or 'when vertical lines can be horizontalized' Abstract: Tensor-network calculus can be done with drawings. Quantum circuits are drawn 'because' they are tensor networks. To foster the full power of diagrammatic simplifications in quantum circuits, some specific tensors and rules governing them are introduced: the ZX calculus. I shall introduce it, exemplify it with the teleportation circuit, and use it to prove the Gottesman-Knill theorem. This talk is based on a presentation by Julien Codsi, at the Bellairs Workshop in March 2023.