# Epistemology

## Quantum Clocks

### An Operationalist Approach to Time in Quantum Mechanics (in Preparation)

Time plays a fundamental role in our understanding of the world around us and we consistently experience things evolving, persisting and perishing. In quantum mechanics, however, time is not usually treated as an observable, but occurs only as a parameter in the equations of motion of physical systems. This is a very unsatisfactory tension which, in our understanding, necessitates an operationalist approach within physics. This means an approach which aims at the conditions under which a concrete interaction between observer and quantum system can occur; and which thus differs, for example, from approaches which start from inner-theoretical considerations about the mathematical formalism of quantum mechanics.

More precisely, this project is concerned with investigating the conditions under which quantum systems can generate something like an objective time scale that is in principle accessible to an observer - i.e., the general conditions for something to act as a quantum clock. Furthermore, the quality of such clocks will be investigated with respect to establishing an earlier-later relation and staying synchronized.

This project has a broad relevance, in particular for current discussions about the emergence of a statistical arrow of time and about retrocausality as a way to overcome the so-called measurement problem of quantum mechanics.

The project is a collaboration with the Chair of Quantum Information Theory at ETH Zurich (Prof. Dr. Renato Renner).

## Epistemology of Spacetime Theories

The epistemology of spacetime theories deals with the question of what we can know about space and time in and by means of our best spacetime theories (such as general relativity). Specifically, the project investigates under what conditions and to what degree the empirical content of general relativity and related spacetime theories can be determined by means of clocks (chronometry).

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