Zenith Grant Awardee

Dr. Markus Aspelmeyer

Institute for Quantum Optics and Quantum Information (IQOQI)

Project Title

Experimental Metaphysics at the Quantum-Classical Border

Project Summary

To what entities do our descriptions of observations refer to in the "real" world? This question is one of the most elementary ones of epistemology and it has undergone a broad spectrum of answers in the course of history, from Berkeley's "esse est percipi" over Kant's unobservable "Thing-in-itself" to Quine's ontological relativism. Due to its successful descriptive models Physics has often served as a guideline to develop these epistemological views, yet they remained basically unchallenged by experimental test. In fact, epistemology has long been considered a purely philosophical field living on a "meta"-level of physics (and it might be even the prevailing view up to date). It was only in the 1960s that John Bell discovered a fundamental incompatibility of certain epistemological views, namely physical realism and locality, with testable predictions of a quantum physics experiment. Since then, many experiments have confirmed that "local realism" is an untenable assumption about the world. Further incompatibility theorems have been put forward, most prominently by Leggett, which leave even less room for the possibility of physical realism as a manifest feature in the world.

Technical Abstract

This project is dedicated to the exploration of the fundamental assumptions about the world that are compatible with experimental observation. It will investigate the possibility for new incompatibility theorems beyond Bell and Leggett, with particular emphasis on including unique features of macroscopic quantum physical systems into the consideration. This will add not only qualitatively new features to the field of "experimental metaphysics," but it might also lead to a better or even new understanding of how physical realism emerges in a classical world. The idea is that macroscopic systems offer unique features of relevance to epistemological concepts such as a well-defined dynamics in phase-space and strict localization in the gravitational field, both of which seem problematic in the context of a quantum description. This leaves room for novel incompatibility theorems that will be testable in the context of quantum experiments on macroscopic quantum systems.

The proposal builds on the results of a previous FQXi project ("Exploring Physical Realism"). While being completely exploratory in nature it tries to take the previous achievements to the next level by combining in a new approach epistemological questions with the clear prospect to design realizable experiments that involve massive mechanical systems.