Bayesian Modelling Approaches for Quantum States -- The Ultimate Gaussian Process States Handbook

TL;DR

This paper introduces Gaussian Process States, a Bayesian framework for modeling quantum many-body wavefunctions, enabling efficient, interpretable, and accurate representations for complex correlated quantum systems.

Contribution

It presents a novel probabilistic ansatz called Gaussian Process State, integrating machine learning techniques for improved quantum state modeling and analysis.

Findings

Effective ground state approximations for quantum lattice models

Successful application to quantum chemical systems

High interpretability and flexibility of the model

Abstract

Capturing the correlation emerging between constituents of many-body systems accurately is one of the key challenges for the appropriate description of various systems whose properties are underpinned by quantum mechanical fundamentals. This thesis discusses novel tools and techniques for the (classical) modelling of quantum many-body wavefunctions with the ultimate goal to introduce a universal framework for finding accurate representations from which system properties can be extracted efficiently. It is outlined how synergies with standard machine learning approaches can be exploited to enable an automated inference of the most relevant intrinsic characteristics through rigorous Bayesian regression techniques. Based on the probabilistic framework forming the foundation of the introduced ansatz, coined the Gaussian Process State, different compression techniques are explored to extract numerically feasible representations of relevant target states within stochastic schemes. By following intuitively motivated design principles, the resulting model carries a high degree of interpretability and offers an easily applicable tool for the numerical study of quantum systems, including ones which are notoriously difficult to simulate due to a strong intrinsic correlation. The practical applicability of the Gaussian Process States framework is demonstrated within several benchmark applications, in particular, ground state approximations for prototypical quantum lattice models, Fermi-Hubbard models and $J_1-J_2$ models, as well as simple ab-initio quantum chemical systems.