Abstract: The ongoing development of powerful quantum computers threatens to render existing cryptographic primitives, based on mathematical complexity, vulnerable to attacks. Quantum Key Distribution (QKD) addresses this by offering a provably secure key exchange mechanism grounded in the laws of physics, ensuring information-theoretic security both today and in the future, even against an adversary with unlimited computing power. Numerous point-to-point QKD demonstrations have been carried out globally, and our research group has also previously demonstrated Coherent One-Way (COW) and Differential Phase Shift (DPS) QKD protocols. Building on these efforts, this work addresses the technical challenges of deploying COW and DPS protocols in field environments and scales them to establish a metropolitan secure access network, termed the “Metro Area Quantum Access Network” (MAQAN).

MAQAN is implemented on the AMD-Xilinx Zynq UltraScale+ hardware platform and demonstrates a hybrid COW/DPS-based QKD network integrated with a post-quantum cryptography (PQC) suite as a fail-safe mechanism. The DPS system operates at 2.5 GHz, while the COW system operates at 1 GHz. The core technology stack comprises an optical layer, a dedicated hardware layer featuring an FPGA-based Quantum Communication Controller and an FMC daughter card that interfaces directly with optical components, a key distillation engine, time-synchronisation, a Software-Defined Networking (SDN) framework, and an ETSI-compliant key management and access interface.

Following the network’s deployment, the research focuses on performance optimisation, specifically jitter analysis and multiprocessing, to reduce the quantum bit error rate (QBER) and enhance secret key generation rates. Finally, a novel “Hierarchical Adaptive XOR-based Alternating Trusted Relay Architecture” is devised to enable long-distance QKD and facilitate future wide-area network expansion.

Event Details
Title: Realising Metropolitan Quantum Access Networks: System Architecture, Performance Optimisation, and Trusted Relay Scaling
Date: October 27, 2026 at 2:00 PM
Venue: ESB 244 / Google Meet (https://meet.google.com/meet/ijf-syxf-qqt)
Speaker: Mr. Vaibhav Pratap Singh (EE20D036)
Guide: Dr. Anil Prabhakar
Type: PHD seminar

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