Fiber-based higher dimensional quantum key distribution implementation using time-bin qudits

Gokul A.; Harinee Natarajan; Varun Raghunathan

doi:10.1117/12.3002155

13 March 2024 Fiber-based higher dimensional quantum key distribution implementation using time-bin qudits

Gokul A., Harinee Natarajan, Varun Raghunathan

Proceedings Volume 12911, Quantum Computing, Communication, and Simulation IV; 129110C (2024) https://doi.org/10.1117/12.3002155
Event: SPIE Quantum West, 2024, San Francisco, California, United States

Abstract

Higher Dimensional Quantum Key Distribution (HD-QKD) improves information capacity and security compared to binary QKD systems. Previous HD-QKD implementations have required d+1 (d refers to encoding dimension) single-photon detectors, limiting large-scale implementation. In contrast, another HD-QKD implementation using coherent one-way (COW) protocol hardware with two detectors achieved a secret key rate (SKR) of 155 kbps for an 8-D system and 2.7% QBER tolerance for a 16-D system with qubit scrambling across a time window. In this paper, we theoretically simulate and experimentally demonstrate time-bin encoded HD-QKD using COW protocol hardware with two single-photon detectors operating at standard telecom wavelengths, achieving a remarkable maximum encoding of 6 bits per photon (i.e., 56-d system). Our HD-QKD system incorporates a practical decoy-state technique to counter the photon number splitting attack, allowing greater flexibility in choosing higher mean photon number thereby achieving higher SKR and distances. This implementation demonstrates a remarkable ninefold increase in SKR for a 16-d system (210 kbps over 25 km of standard single-mode fiber) compared to qubit-based systems, with a QBER tolerance of 13.5% for d = 16. Notably, we achieved positive key rates for emulated loss up to 131 km of fiber length for d = 8. By optimizing detector deadtime and mean photon number using our theoretical model, we achieve enhanced key rates and security. Our findings highlight the superiority of our approach and lay the foundation for high throughput HD-QKD implementation, offering a secure and efficient method for transmitting sensitive information.

Conference Presentation

Citation Download Citation

Gokul A., Harinee Natarajan, and Varun Raghunathan "Fiber-based higher dimensional quantum key distribution implementation using time-bin qudits", Proc. SPIE 12911, Quantum Computing, Communication, and Simulation IV, 129110C (13 March 2024); https://doi.org/10.1117/12.3002155

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