Zenith Grant Awardee

Dr. Caslav Brukner

University of Vienna

Co-Investigators

Tomasz Paterek, <i>University of Vienna</i>

Project Title

Theories of Systems with Limited Information Content – Quantum Theory and Beyond

Project Summary

Quantum theory is our most accurate description of nature. It led to the discovery of the transistor and to understanding of chemistry. In a view of its enormous success, can we consider it as a final ultimate theory? History teaches that a scientific framework accepted at a time, is replaced by more complete description of nature. Flat Earth theory, e.g., accurate for scales much smaller than the Earth's radius, was superseded by spherical Earth theory. History teaches also that new breakthroughs usually require abandonment of old concepts. Insisting on them often led to models of increasing complexity, similar to the Ptolemaic planetary system with numerous epicycles. To date, almost all proposed alternative to quantum theory try to save some of pre-quantum concepts of classical physics. We put forward new theories that share the fundamental features with quantum theory, such as superposition of two distinct states at the same time. All of them are based on the principle of limited information content of physical systems, but differ in the dimensionality of the abstract space in which the system "lives". It is intriguing to speculate that these theories might be realized in Nature in a domain that is still beyond our observations.

Technical Abstract

It is commonly accepted that quantum theory is a singular point with no "neighbor" theories and that any change in its formalism necessarily leads to inconsistencies. At presence, one has considered collapse models as alternatives, which both mathematically and conceptually, are distinctly different and try to save one or the other classical feature. We propose to investigate, both theoretically and by proposing experiments, those alternative theories that share the fundamental, counter-intuitive, features with quantum theory, such as the superposition principle, irreducible randomness of outcomes and entanglement. The key joint feature of the theories is that they all describe systems with fundamentally limited information content. The limit is not due observer's ignorance about the "hidden" properties of the system – the view that would have to be confronted with Bell's theorem – but is of fundamental nature. It is defined operationally with respect to a "black box" as the fundamental restriction on how much information a physical system can carry about the internal configuration of the box. It is intriguing to speculate that either there are additional principle(s) that single out quantum theory, or the alterative ones are also realized in Nature in a domain that is still beyond our observations.