This is part of a virtual seminar series in theoretical condensed matter and atomic physics, with the aim to connect researchers working at different Nordic universities.
Entanglement is central to modern theoretical studies of quantum many-body systems but remains experimentally elusive due to its exponential complexity. Predictions of entanglement phase transitions in monitored quantum systems have further highlighted its importance in far-from-equilibrium states and quantum simulators. However, experimental exploration about manybody entanglement is hindered by the exponential costs of quantum-state tomography and, in monitored systems, by an additional experimentally complex bottleneck of postselection. To address these challenges, I will show how charge fluctuations—or more generally, reduced fluctuations of subsystem observables—can serve as scalable proxies for entanglement entropy, bypassing the need for full-state tomography. For monitored dynamics, I will also discuss a steering protocol that applies adaptive corrective feedback to approximate postselected pure-state trajectories with mixed ensembles of steered states, avoiding full postselection. Numerical simulations and theoretical arguments demonstrate the scalability and efficiency of these methods, with only a polynomial overhead.
Zoom-link: https://nordita.org/zoom/nvcms