Molecular Optimization for Classical and Quantum Condensed Phase Systems

Condensed phase phenomena remain a theoretical challenge to thoroughly understand and elucidate due to the close interactions among large number of microscopic degrees of freedom. Such deviation from the non-interacting ideality necessitates an effective resolution of the constrained fluctuations a...

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Bibliographic Details
Main Author: Shen, Yizhi
Other Authors: Willard, Adam P.
Format: Thesis
Published: Massachusetts Institute of Technology 2023
Online Access:https://hdl.handle.net/1721.1/150557
https://orcid.org/0000-0002-4160-5482
Description
Summary:Condensed phase phenomena remain a theoretical challenge to thoroughly understand and elucidate due to the close interactions among large number of microscopic degrees of freedom. Such deviation from the non-interacting ideality necessitates an effective resolution of the constrained fluctuations and strong correlations in condensed phase systems, which can be methodically achieved using non-Euclidean optimization tools. This thesis is devoted to the optimization-based development of molecular simulations that facilitate our understanding of the static and dynamical properties of many-body systems. Chapter 1 introduces the background on simulating condensed phase systems and sets up the overall scope of the thesis. Chapter 2 provides a primary exposure to a few fundamental connections between functional minimization on manifolds and essential properties, for example statistical and spectral, of many-body systems. Chapter 3 considers methods adept at treating representative classical condensed-phase systems. We start with phenomenological spin models on a lattice and turn our attention to atomistic interfaces including aqueous electrolyte-electrode and polymer-protein composite. We discuss proficient schemes to implement and process our molecular simulations, allowing us to elucidate (a)typical structural-dynamical fluctuations to heterogeneities native to these classical systems. Chapter 4 considers methods capable of studying correlated quantum condensed-phase systems. In particular, we explore the theoretical and numerical underpinnings behind non-parametric simulation schemes that utilize the error-mitigating technique of quantum subspace expansion. We focus on the emergent scenario in which the sub- space is generated by a real-time evolution implemented efficiently on quantum hardware. The practical advantages of the schemes are highlighted through demonstration of their fast and accurate extraction of spectral information.