Null Physics: at the Interface of Quantum Information and Quantum Gravity

Objective

What is the quantum blueprint of spacetime, and which quantum information tools can decode its structure? NPIQIQG addresses fundamental questions in quantum gravity through the lens of quantum information theory, now central to the modern understanding of spacetime. The core idea is to use null hypersurfaces as the scaffolding for this exploration. Null physics offers unique simplifications: null rays follow ultra-local propagation, and the associated Carrollian dynamics is inherently conformal. These properties have enabled key breakthroughs such as the proof of the Generalized Second Law and the formulation of the Quantum Focusing Conjecture, cornerstones of the quantum information approach to gravity. NPIQIQG focuses on the quantum informational content of surfaces, bringing together tools from quantum field theory, perturbative gravity, and operator algebras. The primary goal is to identify and characterize quantum geometric observables on null surfaces and understand their entropic and algebraic structure. In particular, we aim to: 1. Develop a systematic framework for the quantization of geometric data, such as null expansions and area of cuts, ultimately grounding gravitational entropy in the algebraic structure of null hypersurfaces. 2. Establish entropic bounds, modular properties, and quantum information constraints on null hypersurfaces, providing a novel platform to study gravitational subsystems beyond AdS/CFT. This includes flat space and local holography, where we investigate boundary entropic properties and their dual bulk imprints. In a nutshell, NPIQIQG opens a window into the quantum architecture of spacetime, by probing how information is encoded, localized, and retrieved across arbitrary gravitating surfaces.