Constraints on quantum nature of gravity from superposition and entanglement

Abstract

The study of quantum gravity benefits greatly from observational validation. In this thesis, we explore quantum information theoretic aspects of gravity, that can confirm or challenge key assumptions and properties expected of a quantum theory of gravity with the aim of validating and distinguishing between different classes of gravitational theories. Specifically, we identify and analyze three possible classes: mean-field classical, classical field with quantum interactions, and fully quantum theories. We begin by reviewing the notions of quantumness and locality, providing a framework for understanding their implications in gravitational contexts. We then propose observations of superposed primordial massive particles as a method to distinguish mean-field classical theories from others. Further, we discuss entanglement as a witness to fully quantum gravitational theories following the BMV proposal, arguing that while certain specific semi-classical theories might produce entanglement, these are "rule book" theories and lack a fundamental notion of causality.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Yi WANG (Supervisor)