Quantum Gravity and Quantum Information

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This project lies at the interface of quantum gravity and quantum information. The cross-fertilization of these two sub-fields is at the roots of a number of foundational results in theoretical physics related to the interface between gravity and quantum mechanics. The goal of this project is to develop new quantum-information methods and apply them to the exploration of the quantum nature of spacetime. The results of this research are expected to have a direct impact on the development of loop quantum gravity (LQC), a theory that unifies gravitation with all the other forces of nature, and of the understanding of the interplay between these forces in the very early universe.In the context of loop quantum gravity, methods from condensed-matter physics are applied to spin-network states to identify the corner of the kinematical Hilbert space which supports quantum geometries with long-range correlations. In particular, typicality and eigenstate thermalization in a new fermionic representation of the spin 1/2 truncation is employed. At the dynamical level, methods from causal networks are applied to spin-foams to identify classes of configurations with a fixed global causal structure and determine the effective Lagrangian of the theory. At the perturbative level, the entanglement production by quantum fields in cosmological spacetimes is studied, with a focus on the pre-inflationary phase. The objective is to identify quantum-information quantities, such as the mutual information between regions of spacetime, that describe universal features of the transition between the non-perturbative quantum gravity phase and the perturbative effective-field-theory regime.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.