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Q: Fachverband Quantenoptik und Photonik

Q 20: Quantum Gases: Bosons II

Q 20.7: Vortrag

Dienstag, 7. März 2023, 12:30–12:45, F342

Full quantum simulations of Bose gases with the complex Langevin method — •Philipp Heinen and Thomas Gasenzer — Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg

While path integrals can be straightforwardly evaluated by standard Monte Carlo methods in the case of a real action, these are not applicable for a complex action because the interpretation of the integrand as a probability density is lost in this case, a fact that is commonly known as sign problem. This hinders ab initio simulations of the interacting Bose gas in the field-theoretic framework, since the purely imaginary Berry phase term in its action causes a sign problem even in thermal equilibrium. The complex Langevin (CL) algorithm is a generic, model-independent approach to tackle the sign problem by recasting the path integral into a stochastic Langevin equation and by complexifying the originally real degrees of freedom of the problem. While it has a long-standing history in high energy physics, its application to ultracold atoms is rather recent. In my talk I want to demonstrate that CL is able to simulate interacting bosons from first principles and show applications to the BKT transition and the physics of dipolar Bose gases.