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Optical Fiber Communication Conference

A Silicon Photonic Chip-based System for 2.5-GHz Quantum Key Distribution (QKD)

Wei Luo, Lushuai Cao, Hong Nian Cai, Muhammad Faeyz Karim, L. C. Kwek, A. Q. Liu

Published Jan 1, 2024• 4 citations
Publisher

Abstract

We have demonstrated a compact, chip-based system for high-speed polarization-encoded QKD, which utilizes advanced silicon photonics technology and operates at a clock rate of 2.5 GHz. Our design enables secure key rates up to 1.018 Mbps at equivalent fiber distance of 100 km in the finite-size regime. The results of the proof-of-principle experiment indicate that this high-speed, chip-based QKD system is a viable, high-performance solution well-suited for upcoming quantum communication applications.

DOI
10.1364/ofc.2024.th2a.9

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Photonic integrated circuits provide a compact and stable platform for quantum photonics. Here we demonstrate a silicon photonics quantum key distribution (QKD) encoder in the first high-speed polarization-based QKD field tests. The systems reach composable secret key rates of 1.039 Mbps in a local test (on a 103.6-m fiber with a total emulated loss of 9.2 dB) and 157 kbps in an intercity metropolitan test (on a 43-km fiber with 16.4 dB loss). Our results represent the highest secret key generation rate for polarization-based QKD experiments at a standard telecom wavelength and demonstrate photonic integrated circuits as a promising, scalable resource for future formation of metropolitan quantum-secure communications networks.
Abstract Quantum communication has extremely high security and is a development direction of future communication networks. In this paper, an on-chip path, off-chip polarization encoded quantum key distribution (QKD) chip is designed and fabricated using advanced silicon photonics fabrication technology. Using a special two-dimensional grating, we can convert light of different path states into corresponding polarization states and propagate in fiber. The performance of the basic optics, waveguides, gratings, and Mach–Zehnder interferometers on the chip is characterized. In the demonstrated QKD experiment, the quantum bit error rate is as low as 1.08%. It provides an important device for the future development of advanced integrated quantum information.
Quantum key distribution (QKD) enables secure communication by harnessing the fundamental principles of quantum physics, which inherently guarantee information-theoretic security and intrinsic resistance to quantum computing attacks. However, the secure key rate of QKD typically decreases exponentially with increasing channel distance. In this work, by developing a novel polarization-state preparation method, an ultra-low time-jitter laser source and superconducting nanowire single-photon detectors, we demonstrate a 5-GHz integrated QKD system featuring ultra-low quantum bit error rates (QBERs). The system achieves secure key rates of 1.076 Mbps at 150 km and 105 kbps at 200 km over standard single-mode fiber channels, respectively. Our system substantially enhances the secure key rate, enabling high-resolution video calls with one-time-pad encryption over intercity backbone QKD links. This work represents a significant step forward in the development of high-performance practical QKD systems.