PAST OF A QUANTUM PARTICLE AND QUANTUM INFORMATION PROCESSING WITH OPEN-SYSTEM NOISE

Abstract

This thesis consists of two parts: (I) past of a quantum particle, and (II) quantum information processing with open-system noise.

In Part I, we study the path taken by a quantum particle, after it has traversed an interferometer. In our analysis, “the particle’s path” has operational meaning as acquired by a path-discriminating measurement. We show that the particle’s path through the interferometer can be understood with common sense. Furthermore, we perform an experiment and obtain results that strongly support our theoretical analysis.

In Part II, we study the performance of quantum error correction (QEC) on a system undergoing an open-system (OS) dynamics—the noise on the system originates from a joint quantum channel on the system-bath composite. We derive the conditions for perfect correctability, and provide a lower bound for the OSQEC performance when the noise is approximately correctable. As the initial state is important for specifying the dynamics of open systems, we also study the extraction of information about the system-bath initial state with measurements on the system alone.