Information processing with Page-Wootters states

TL;DR

This paper explores how quantum mechanics constrains the use of entangled photons to define a clock and copy system states, addressing fundamental questions about quantum time evolution.

Contribution

It analyzes the limitations quantum mechanics imposes on establishing a quantum clock and copying states, informed by recent experimental results.

Findings

Quantum mechanics restricts the ability to perfectly copy quantum states.

Entangled photons can be used to implement quantum clocks under certain conditions.

Experimental insights highlight the constraints on quantum state replication and time measurement.

Abstract

In order to perceive that a physical system evolves in time, two requirements must be met: (a) it must be possible to define a "clock" and (b) it must be possible to make a copy of the state of the system, that can be reliably retrieved to make a comparison. We investigate what constraints quantum mechanics poses on these issues, in light of recent experiments with entangled photons.