Entanglement and Quantum Information Transfer in Arrays of Interacting Quantum Systems

TL;DR

This thesis explores quantum information transfer and entanglement creation in neutron systems and dipolar spin chains, highlighting methods for efficient quantum communication and the physical interpretation of scattering experiments.

Contribution

It demonstrates neutron entanglement via forward-scattering and analyzes quantum information transfer in dipolar spin chains, proposing optimization strategies.

Findings

Neutron spins can be measurably entangled through forward-scattering.

Dipolar spin chains enable high-fidelity long-distance quantum state transfer.

Transfer times in unmodulated chains are impractically long, but optimization is possible.

Abstract

This thesis examines some of the more fundamental requirements of a successful quantum computation, namely the ability to transmit quantum information with maximum efficiency, and the creation of entanglement. I focus specifically on neutron entanglement, showing that the spins of two or more distinct neutrons can be measurably entangled by forward-scattering from an isotropic medium. The interpretation of `time' in scattering experiments is also discussed. I present a simple treatment based on the Heisenberg S-matrix, from which it emerges that in certain situations the quantum-mechanical time parameter appearing in the effective time-evolution operator for the spin system has an intuitive physical interpretation. The final part of the thesis deals with quantum information transfer in arrays of permanently coupled dipolar systems. It is shown that spin chains with dipolar couplings offer high fidelity long-distance state transmission, but transfer times in unmodulated chains are unfeasibly long. Possible optimization methods are discussed, concluding with a review of recent achievements in this field.