The time as an emergent property of quantum mechanics, a synthetic description of a first experimental approach

TL;DR

This paper presents an experimental approach using entangled photons to demonstrate how time can emerge as a property within quantum mechanics, supporting the idea that subsystems can serve as clocks in a static universe.

Contribution

It provides the first experimental demonstration of a subsystem acting as a clock within an entangled quantum state, illustrating the emergence of time.

Findings

Subsystems in entangled states can serve as clocks.

Experimental validation of the Page-Wootters mechanism.

Supports the view of time as an emergent property in quantum mechanics.

Abstract

The "problem of time" in present physics substantially consists in the fact that a straightforward quantization of the general relativistic evolution equation and constraints generates for the Universe wave function the Wheeler-De Witt equation, which describes a static Universe. Page and Wootters considered the fact that there exist states of a system composed by entangled subsystems that are stationary, but one can interpret the component subsystems as evolving: this leads them to suppose that the global state of the universe can be envisaged as one of this static entangled state, whereas the state of the subsystems can evolve. Here we synthetically present an experiment, based on PDC polarization entangled photons, that allows showing with a practical example a situation where this idea works, i.e. a subsystem of an entangled state works as a "clock" of another subsystem.