Zenith Grant Awardee

Dr. Markus Aspelmeyer

Institute for Quantum Optics and Quantum Information (IQOQI)

Co-Investigators

Caslav Brukner, <i>University of Vienna</i><br>Keith Schwab, <i>Cornell University</i><br>Vlatko Vedral, <i>Leeds University</i><br>Anton Zeilinger, <i>IQOQI</i>

Project Title

Expolring Physical Realism – Experiments on the Foundations & Limits of Quantum Physics

Project Summary

Two important fundamental questions are presently left unanswered by physics: "Why the quantum?" and "Why the classical?" The first question arises from our inability to provide a simple epistemological basis for quantum phenomena, above all quantum superposition and entanglement. Different interpretations claim to provide an explanation for the same phenomena and are yet founded on fully incompatible principles. A well-known example is the striking contradiction between the underlying assumptions of the Copenhagen interpretation and the realistic model of Bohm. The second question addresses the yet unresolved problem whether classicality can emerge from a quantum physical description of the world. Conceptual difficulties arise when quantum physics is applied consequently to increasingly massive and complex systems. Schrodinger's famous "cat"-example was the first to point out the dramatic, contra-intuitive consequences of the possibility of macroscopic entanglement for our understanding of the world.

Our research aims to provide a better understanding of the nature of physical reality based on these two fundamental questions. We will both explore the consequences of a realistic description of the quantum world and test experimentally to which extent the present boundary between the quantum and the classical world can be exploited – if it exists at all.

Technical Abstract

The objective of the project is to provide, both in theory and in experiment, a deeper understanding of the nature of physical reality. One line of research ("Why the quantum?") will be based on experiments with entangled photons designed to explore the foundations of quantum phenomena in a regime where quantum physics is known to hold and where alternative underlying theories still exist. A specific goal is to test quantum physics against classes of hidden-variable models that are not covered by Bell's theorem, in particular non-local realistic theories. Can such theories be experimentally ruled out as foundational basis for quantum theory, similar to the successful Bell-experiments that could rule out all local-realistic theories? Another line of research ("Why the classical?") will exploit an up to now unexplored experimental regime, in which quantum physics is believed to hold but has not yet been tested. Specifically, experiments will be devised and performed that involve macroscopic mechanical resonators of up to 10^22 atoms. The experiments aim to observe quantum superposition and quantum entanglement in seemingly classical systems. These configurations will allow to formulate Bell-like theorems and to investigate the underlying structure of the classical world – and its compatibility with a quantum description.