Charu Jain

We describe the development of the NetQStack Simulator, a network-integrated simulation framework designed to evaluate distributed quantum computing (DQC) within data center environments. Our approach strictly models the network topology, classical control plane, and quantum data plane required to execute distributed quantum workloads. The simulator models classical and physical-layer protocol synchronization, schedules sub-circuit executions on individual Quantum Processing Units (QPUs), and routes entanglement generation requests across Bell State Measurement (BSM) nodes. With the ability to use external network-aware circuit partitioning software, and interface with an intelligent quantum network controller, this architecture enables researchers to execute fully distributed algorithms while rigorously evaluating the impact of network latency, routing heuristics, and control-plane overhead. Our early results demonstrate that a network-integrated approach provides useful insights when assessing the performance and scalability of distributed quantum algorithms.

Scaling quantum networks to long distances necessitates the development of advanced Quantum Repeater (QR) technologies. Depending on the error mitigation mechanisms adopted to suppress loss and errors, QRs are typically classified into memory-based or all-photonic QRs; and each type of QR may be best suited for a specific type of underlying quantum technology, a particular scale of quantum networks, or a specific regime of operational parameters. This paper presents a comparative theoretical and simulation-based analysis of first-generation memory-based trapped-ion QRs and networks, and all-photonic entanglement-based QRs and networks. Our model incorporates a wide range of realistic parameters and noise sources to evaluate performance trade-offs. Major research findings of this study include: (a) the entanglement rate does not necessarily scale with the number of quantum repeaters. Although adding repeaters in a chain helps to reduce photon loss in quantum links, it also introduces overheads that can be attributed to imperfect photon collection, inefficient quantum frequency conversion, and limited detector efficiency. The entanglement rate only improves when the distance between QRs exceeds a certain threshold, specifically, when the reduction in photon loss in quantum links gained by adding QRs outweighs the inherent overheads they introduce. (b) Without quantum error correction and entanglement purification, the entanglement fidelity decreases with the number of QRs, regardless of the chain distance. Finally, the theoretical models and simulation software package developed in this study provide a versatile framework for the design and evaluation of future QR technologies, protocols, and architectures.