Date of Award

Spring 2002

Document Type

Restricted Thesis

Terms of Use

© 2002 Robert N. McFarland. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Physics & Astronomy Department

First Advisor

John R. Boccio


We discuss the nature and role of the measurement problem in quantum mechanics and present the concept of decoherence as a proposed solution to the measurement problem. We review important conceptual foundations for understanding both the problem and the proposed solution, including axiomatic formulations of quantum theory and the dens it operator formalism. We then present a simple yet physically realistic model of a measurement interaction, in which the spin of a spin-112 particle is measured using a Stern-Gerlach type device in the presence of an ideal gas environment. The model is solved first in the absence of an environment and then with the bath present. We demonstrate decoherence in the latter case and discuss the numerical predictions, analyzing possible problems in the model or calculation. Finally, we discuss the implications of a decoherence-based view of quantum measurement and consider the impact of such a model on interpretations of quantum mechanics.