Date of Award
5-9-2025
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Recent advancements in quantum computing have opened up new possibilities across various fields, offering significant potential to enhance computation, communication, cryptography, and applications in areas like sensing, medicine, and chemistry. However, the capabilities of individual quantum devices are still limited, and scaling quantum hardware monolithically presents substantial challenges. Interconnecting quantum systems offers a promising alternative by aggregating capabilities across a network, thereby enabling quantum advantages for larger and more practical problems. This interconnection is achieved through quantum networking, which links external quantum systems, and Distributed Quantum Computing (DQC), which connects quantum processors within a system, such as in quantum data centers. As the scale of interconnected systems increases, security concerns associated with their integration also grow. To advance quantum networking and DQC techniques, numerous models of quantum repeaters and switches have been proposed, each presenting distinct strategies for enabling quantum communication over long distances. Our focus is on repeaters that leverage entanglement generation and swapping, known as “quantum-native” or “first-generation” repeaters. These repeaters face challenges stemming from the probabilistic nature of entanglement generation and limited coherence times. To address these challenges, this dissertation examines the core principles of quantum networking, DQC, and quantum network security, and presents our contributions to these fields. In particular, we propose Asynchronous Entanglement Routing (AER) to eliminate the need for synchronized operations required by existing approaches and to preserve unused entanglement links, significantly enhancing the efficiency of End-to-End (E2E) entanglement distribution. AER operates in a distributed manner using only local neighbor information for routing, employing structures such as Destination-Oriented Directed Acyclic Graphs (DODAGs) or distributed spanning trees. By mitigating delays caused by network-wide updates, AER significantly improves practicality for quantum applications. Our results demonstrate that AER achieve a higher upper bound and significantly increase the entanglement rate compared to existing synchronous approaches. The practicality and efficiency gains suggest that AER will have a substantial impact on quantum networks as technology progresses. We further extend AER to a multi-tree networking scheme to accommodate larger-scale quantum networks. This approach connects multiple DODAGs in a distributed manner, achieving a higher E2E entanglement generation rate in a practical and asynchronous fashion, while still relying solely on the local knowledge of each node’s entanglement links. Testing on both generated and realistic topologies indicates that the multi-tree approach outperforms single-tree and synchronous routing schemes in terms of entanglement rate and efficiency. This work highlights the effectiveness of asynchronous routing strategies for diverse quantum network topologies and presents a superior routing solution. In addition to interconnecting external quantum systems, the need for linking Quantum Processing Units (QPUs) within a single system has also grown, driving the expansion of DQC architectures. In a quantum data center with multiple QPUs distributed across different racks, executing remote gates requires entanglement between distinct QPUs. However, generating this entanglement often leads to congestion and resource contention. To address this, we propose a resource management framework that maximizes fidelity-guaranteed throughput while maintaining dependencies. We formulate the problem as a Mixed-Integer Linear Programming (MILP) model for benchmarking and introduce efficient heuristic scheduling algorithms. Simulations show that these heuristics closely approximate the solver’s results, demonstrating their practicality for managing remote gates and improving overall performance. Despite the enhanced security that quantum networks offer over traditional systems, the quantum internet still faces unique security challenges crucial for ensuring its Confidentiality, Integrity, and Availability (CIA). We examine these challenges by analyzing vulnerabilities and potential mitigation strategies across different layers of the quantum internet, including the physical, link, network, and application layers. We assess the severity of potential attacks and evaluate the effectiveness of corresponding countermeasures, integrating both classical and quantum approaches. The findings highlight the dynamic nature of security risks and emphasize the need for adaptive security measures. It underscores the need of continuous exploration into the security aspects of the quantum internet to enhance its robustness and facilitate its widespread adoption. We further explore quantum-era cryptographic applications through a theoretical analysis of quantum blockchains for decentralized identity authentication. It includes a proposed conceptual framework, a review of supporting technical evidence, and an evaluation of its core components, feasibility, effectiveness, and limitations.
Language
English (en)