Qiss

The possibility of a future `table top’ Quantum Gravity test has been much discussed the past years. I will discuss the family of `standard’ protocols that envision entanglement production between spatially delocalised particles, the controversy surrounding the topic with respect to a `theory fixed’ vs a `theory independent’ interpretation and the related confusion on the assumption of `locality’ and the `mediating degree of freedom’. I will also discuss alternative protocols involving macroscopic quantum systems like bose einstein condensates, a genuine relativistic test involving superposition of rotations (superposition of mass), as well as these ideas may be leveraged also for the detection of Planck mass dark matter particles (which could be tiny black/white holes!).

I will sketch the toolbox and achievements of modern lattice quantum gravity, aka solving the full 4D Lorentzian gravitational path integral, using causal dynamical triangulations (CDT). It provides us with a long-sought window on physics in a near-Planckian regime, where geometry is highly nonclassical and not describable in terms of standard tensor calculus. With concrete answers to longstanding issues of how to properly implement diffeomorphism invariance, causal structure and Wick rotation, we are now focusing on interesting, approach-independent questions on the nature of nonperturbative quantum gravity and its observables. Based on results on the dynamical emergence of a 4D universe with de Sitter properties from first principles, early-universe cosmology may be our best bet in terms of quantum gravity phenomenology.

Quantum networks are the center of many of the recent advances in quantum science, not only leading to the discovery of new properties in the foundations of quantum theory but also allowing for novel communication and cryptography protocols. It is known that networks beyond that in the paradigmatic Bell’s theorem imply new and sometimes stronger forms of nonclassicality. We will review some recent experiments addressing non-classicality in different network structures.