Observation of quantum anomalies and topological quantum matter using an ultracold quantum simulator

by Mr Nehal Mittal (Laboratoire Kastler Brossel, ENS Paris, France)

Tuesday 10 Mar 2026, 15:30 → 16:30 Asia/Kolkata

D405 and on Zoom

Symmetry is a central organising principle of modern physics, shaping the laws of nature through invariance structures that constrain dynamics, enforce conservation laws, and unify interactions from classical mechanics to quantum field theory. Yet not all symmetries survive quantisation: in field theory, a symmetry is said to be anomalous when it cannot be consistently preserved at the quantum level. Quantum anomalies leave measurable fingerprints across physics, governing classically forbidden processes such as the rapid decay of the neutral pion into two photons and placing powerful constraints on low-energy effective field theories through ’t Hooft anomaly matching. In many-body systems with boundaries, anomalies give rise to phenomena such as bulk-edge correspondence and quantised topological response via anomaly inflow.

In this talk, I will introduce ultracold atomic gases as highly controllable platforms for exploring concepts at the interface of condensed-matter physics, high-energy physics, and quantum information science. I will then review key ideas in topological matter and describe our experimental realisation of quantum Hall physics in both (2+1)- and (4+1)-dimensional settings, achieved by coupling a continuous spatial dimension to a finite synthetic dimension encoded in atomic spin states of ultracold dysprosium atoms. Finally, I will present our observation of parity anomaly at the critical point of a topological phase transition, between Chern bands with C = 0 and C = 1.