Qubit clock in quantum cosmology

TL;DR

This paper explores how a qubit-based clock in quantum cosmology can lead to the emergence of time through entanglement, resulting in a Schrödinger evolution of the universe's wave function.

Contribution

It introduces a quantum cosmological model with a qubit clock demonstrating how entanglement induces the emergence of time and affects the universe's energy content.

Findings

The universe's wave function obeys the Schrödinger equation conditioned on the qubit clock.

Entanglement between the universe and the clock is quantified by Fisher information.

Fisher information acts as a negative energy density in the model.

Abstract

We investigate the emergent time scenario in quantum cosmology based on the Page-Wotters approach. Using a quantum cosmological model with a qubit clock, it is demonstrated how the entanglement between the qubit clock and the geometry derives emergence of a time parameter which defines evolution of the timeless quantum state of the universe. We show the universe wave function conditioned by a qubit clock obeys the standard Schr\"{o}dinger equation and the Fisher information for the clock state, which quantifies entanglement between the universe and the clock, contributes as a negative energy density.