Towards quantum networks: Theory, experiment, and applications

Quantum information science integrates the concepts of quantum mechanics and information science to examine the processing, transmission, and analysis of information. This multidisciplinary field encompasses both theoretical and experimental aspects of quantum physics, aiming to explore the limits of what can be achieved with quantum information technologies. In this thesis, we delve into both the theoretical frameworks and experimental investigations within quantum information science, placing a particular focus on photonic quantum systems. We introduce new findings across three main areas of quantum information science: (a) the development of a photonic information processing system, which includes the design and implementation of single-photon sources, quantum channels, and detectors; (b) the introduction of innovative applications in quantum information science, specifically leveraging entanglement (coherence) in multiple-access channels and for quantum telescopy; and (c) a deeper exploration into the foundations of quantum mechanics through the study of the generation, manipulation, and measurement of non-classical quantum correlations. To connect the study of diverse quantum information problems addressed in this thesis, we will first illustrate their collective relevance to the advancement of quantum networks -- an interconnected information-processing system that remains challenging to build up on a large-scale network, while simultaneously leading to the creation of revolutionary quantum technologies. In the first part, we will focus on the entanglement generation layer of quantum networks, where the generation and distribution of an efficient single-photon source and entangled photon-pair source are required. We will detail our experimental works on the design of factorable photon-pair sources based on both the spontaneous four-wave mixing (SFWM) and spontaneous down-conversion (SPDC) processes. These sources are important for numerous quantum operations where the purity of the single-photon state is of paramount importance. Moving to the second part, the focus shifts to the application layer of the quantum network. Here, we explore both the theoretical framework and experimental realization of two different quantum protocols: multiple-access quantum communication and quantum-enhanced telescopy. This discussion aims to underscore the significant advantages that quantum resources, particularly single-particle quantum entanglement, offer in the realms of communication, sensing, and beyond in information-theoretical applications. In the last part, we delve into the fundamental aspects of non-classical quantum correlations from a theoretical perspective, focusing on their generation through non-classical quantum states, the influence of noisy quantum channels, and the role of non-classical quantum measurements. Firstly, concerning noisy quantum channels, we present a series of channel activation results demonstrating how the collective use of multiple noisy quantum channels can facilitate nonlocal distribution while each channel cannot. In the realm of non-classical quantum states, we introduce and elaborate on the concept of the simulation cost of a quantum state. This metric serves to quantify the degree of 'quantumness' of an unsteerable state. Our findings reveal that all entangled quantum states necessitate a higher simulation cost in the qubit framework, highlighting that certain quantum states, despite being theoretically simulatable, require unbounded resources for practical simulation. Finally, we address a longstanding question in quantum information science, identified as problem 39 in the list of open quantum problems in Vienna. We establish that positive operator-valued measurements (POVMs) do not provide greater non-classicality than projective-valued measurements (PVMs) in the quantum steering of noisy Werner states. This conclusion clarifies the limitations and capabilities of POVMs in enhancing non-classicality under specific conditions. However, we also identify scenarios where the distinction between POVMs and PVMs becomes evident, particularly in contexts where classical resources are constrained. This nuanced understanding of measurement-induced non-classicality contributes significantly to the broader discourse on quantum measurement theory and its implications for quantum information processing.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Zhang, Yujie

Contributors dc:contributor

• Lorenz, Virginia O
• Chitambar, Eric
• Kwiat, Paul G
• Junge, Marius

• Quantum Information
• Quantum Optics
• Entanglement Theory
• Quantum Network
• Quantum Communication
• Quantum Telescope

Statement dc:rights

• Copyright 2024 Yujie Zhang

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/124155

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F124155