Relativistic quantum information theory and quantum reference frames

TL;DR

This thesis develops a relativistic quantum information framework for localized qubits in curved spacetime and explores quantum reference frames, revealing how changing frames induces decoherence and advancing the understanding of quantum relativity.

Contribution

It introduces a fundamental construction of quantum information theory for localized qubits in curved spacetime and analyzes quantum reference frames, including decoherence effects.

Findings

Quantum experiments on photons and electrons near Earth modeled.

Decoherence is induced when changing quantum reference frames.

A theoretical basis for quantum relativity principles established.

Abstract

This thesis is a compilation of research in relativistic quantum information theory, and research in quantum reference frames. The research in the former category provides a fundamental construction of quantum information theory of localised qubits in curved spacetimes. For example, this concerns quantum experiments on free-space photons and electrons in the vicinity of the Earth. From field theory a description of localised qubits that traverse classical trajectories in curved spacetimes is obtained, for photons and massive spin-1/2 fermions. The equations governing the evolution of the two-dimensional quantum state and its absolute phase are determined. Quantum information theory of these qubits is then developed. The Stern-Gerlach measurement formalism for massive spin-1/2 fermions is also derived from field theory. In the latter category of research, the process of changing reference frames is considered for the case where the reference frames are quantum systems. As part of this process, it is shown that decoherence is necessarily induced on any quantum system described relative to these frames. This process is explored using examples involving quantum reference frames for phase and orientation. Quantifying the effect of changing quantum reference frames provides a theoretical description for this process in quantum experiments, and serves as a first step in developing a relativity principle for theories in which all objects including reference frames are necessarily quantum.