Quantum Foundations

In classical systems, the Kolmogorov–Arnold–Moser (KAM) theorem establishes that resonant tori of integrable Hamiltonians are destroyed by any nonintegrable perturbation, whereas nonresonant tori are only deformed up to a finite value of the perturbation parameter. In this seminar, we explore a…

Measurement is a fundamental ingredient of quantum theory, and reasonably well-understood in non-relativistic quantum mechanics. In contrast, relativistic requirements of locality and causality have provided a challenge for measurement in quantum field theory, as highlighted by Sorkin's seminal work…

Local indistinguishability - often called "quantum nonlocality without entanglement" (QNLWE) - describes the counterintuitive situation where orthogonal product states cannot be discriminated by local operations and classical communication (LOCC). Kunjwal and Baumeler [PRL 131, 120201 (2023)] showed…

Although there are good reasons to believe that quantum states are sometimes relativized to observers, there are difficulties for the view that quantum states can only be relativized to conscious macroscopic observers, and also for the view that quantum states can be relativized to any physical…

The study of quantum correlations in multipartite network scenarios represents a significant extension of nonlocality research beyond the standard Bell–CHSH framework. Quantum networks comprise multiple parties interconnected by several independent quantum sources that distribute quantum states…

At the heart of both Wigner's friend paradoxes and black hole puzzles lies the question of unitarity. In Wigner’s friend setups, sealed-lab measurements are modeled unitarily, probing the measurement problem. In black hole physics, the unitarity problem concerns information preservation in…

Causal interventions have emerged as an effective tool for certifying nonclassicality, offering improved detection efficiency and robustness to noise compared to purely observational approaches. However, standard node interventions (Pearl interventions) become uninformative in space-like separated…

The study of foils, or "mutations", of quantum theory has proven to be extremely useful in identifying operational reasons for why quantum theory is the way it is. In this talk, I will present our work on a mutation of quantum theory via its geometric formulation. The observational signatures (…

In 2017, Scellier and Bengio introduced the machine learning algorithm known as Equilibrium Propagation, in which the stationary state of a dynamical system is exploited for computation. A canonical example involves a network of nonlinear coupled elements -such as springs- described by a Hamiltonian…

Non-local games are a powerful tool to distinguish between correlations possible in classical and quantum worlds. Kalai et al. (STOC’23) proposed a compiler that converts multipartite non-local games into interactive protocols with a single prover, relying on cryptographic tools to remove the…

Purification theorems play a crucial role in quantum information, showing that mathematical models of quantum states and operations relate to physically realisable circuits. A long standing line of research has been concerned with the problem of finding appropriate conditions for simultaneous…

Abstract: In this talk, I will present our recent results in https://arxiv.org/abs/2507.14278: The statistics of local measurements of joint quantum systems can sometimes be used to distinguish the spatiotemporal structure in which they were measured. We first prove that every bipartite separable…