Relativistic quantum information and time machines

TL;DR

This paper reviews the emerging field of relativistic quantum information, focusing on how quantum systems interact with closed timelike curves, and discusses models that avoid paradoxes in quantum time travel.

Contribution

It introduces two approaches for modeling quantum systems with time machines, highlighting the density operator matching method as more consistent.

Findings

Density operator matching avoids paradoxes

Two modeling approaches for quantum time machines

Insights into quantum information in curved spacetime

Abstract

Relativistic quantum information combines the informational approach to understanding and using quantum mechanics systems - quantum information - with the relativistic view of the universe. In this introductory review we examine key results to emerge from this new field of research in physics and discuss future directions. A particularly active area recently has been the question of what happens when quantum systems interact with general relativistic closed timelike curves - effectively time machines. We discuss two different approaches that have been suggested for modelling such situations. It is argued that the approach based on matching the density operator of the quantum state between the future and past most consistently avoids the paradoxes usually associated with time travel.