Zenith Grant Awardee
Stefano Pironio
Universite Libre de Bruxelles
Co-Investigators
Lluis Masanes, ICFO; Robert Spekkens, Perimiter Institute for Theoretical Physics
Project Title
Time and the Structure of Quantum Theory
Project Summary
It is common to be in a state of bewilderment after reading a popular account of quantum theory. After all, physicists and philosophers are still trying to make sense out of the numerous puzzles and paradoxes of the theory, such as Schrodinger's cat, the impossibility of determining unambiguously the polarization state of a photon by measuring it, or the mysterious faster-than-light connection between distant particles. It is rarely stressed, though, that these weird quantum effects are deeply connected to issues about the nature of time. If Schrodinger's cat must end up alive or dead, it is hard to maintain a time-reversible picture of quantum evolution. A measurement apparatus able to determine the polarization state of an arbitrary photon would contradict the second law of thermodynamics. The spooky action-at-a-distance between quantum particles can be accounted for if the future can influence the past. What does quantum theory tell us about time? Can facts about time help us interpret the mathematical formalism of quantum theory or understand why Nature chose this theory? We will address these questions in the context of a very new area of research, wherein probabilistic models more general than quantum theory are developed and explored.
Technical Abstract
The project aims to investigate the connections between the nature of time and the mathematical formalism of quantum theory. We want to know what quantum theory tells us about time and conversely, if facts about time could explain why quantum theory has the particular structure that it does.
The project will address these questions in the context of a new but very active area of research, wherein probabilistic models more general than quantum theory are developed and explored. Work in this area to date has focused on the information-theoretic properties of different sorts of theories. The project will establish an entirely new direction, which is to consider the nature of time, rather than information in a general framework.
The broad aims are
- A fundamental understanding of the constraints that assumptions about time, such as reversibility, place on the structure of physical theories.
- An identification of the properties that a probabilistic theory must have in order to admit a notion of thermodynamic entropy or for the second law of thermodynamics to hold.
- Investigating whether a model with no unique direction of causation can provide a common-cause explanation of nonlocal correlations while also entailing the absence of superluminal signalling.
QSpace Latest
PressRelease: Shining a light on the roots of plant “intelligence”
All living organisms emit a low level of light radiation, but the origin and function of these ‘biophotons’ are not yet fully understood. An international team of physicists, funded by the Foundational Questions Institute, FQxI, has proposed a new approach for investigating this phenomenon based on statistical analyses of this emission. Their aim is to test whether biophotons can play a role in the transport of information within and between living organisms, and whether monitoring biophotons could contribute to the development of medical techniques for the early diagnosis of various diseases. Their analyses of the measurements of the faint glow emitted by lentil seeds support models for the emergence of a kind of plant ‘intelligence,’ in which the biophotonic emission carries information and may thus be used by plants as a means to communicate. The team reported this and reviewed the history of biophotons in an article in the journal Applied Sciences in June 2024.