Michael Kaicher, "Mean-Field Theory for Real- and Imaginary-Time Evolution in Interacting Spin-½ Systems"

Wednesday 11 Jun 2025, 12:00 → 13:00 Europe/Berlin

Abstract:  With the increasing size and controllability of modern quantum simulators, benchmarking experimental results against numerical simulations becomes increasingly challenging. In this work, we present two efficient mean-field approaches based on bosonic and fermionic Gaussian states. These methods enable the real- and imaginary-time evolution of large spin-½ systems with arbitrary geometries and interactions, extending conventional spin mean-field theory by incorporating quantum fluctuations within the Gaussian approximation. 
We derive numerically stable equations of motion for the bosonic variational parameters and extend the fermionic Gaussian mean-field formulation beyond fermionic parity-conservation. This advancement allows, for the first time, fermionic Gaussian states to represent general spin-½ Hamiltonians. As a case study, we examine the limitations of Gaussian mean-field methods in simulating a quantum quench of the transverse-field Ising model (TFIM) in two dimensions, comparing our results with state-of-the-art techniques.