QKD System Performance — Part 1
Quantum Key Distribution (QKD) systems manifest through diverse protocols with varying strengths and constraints. Entanglement protocol-based QKD relies on generating and transmitting entangled photon pairs, offering compatibility with the prospective quantum Internet architecture but grappling with entanglement yield and fidelity limitations. Conversely, preparation-measurement protocols-based QKD, encompassing discrete (DV) and continuous variables (CV) implementations, exploits diverse optical signal degrees of freedom, like polarization, phase, and pulse phase difference. However, the key rate of these systems is influenced by transmission efficiency and the inherent loss constraints of optical fiber channels.
Since 2018, the twin-field (TF) QKD protocol has gained traction. Its dual-end preparation and center measurement architecture mitigates side-channel vulnerabilities, enhances theoretical secure key rates tied to transmission efficiency, and surpasses the PLOB boundary of quantum channel capacity. Noteworthy advancements include the sending-or-not-sending (SNS) protocol, the two-way classical communication (TWCC) method, and the active odd-parity paring method, elevating TF-QKD as a future-ready solution for long-range, high-security QKD. These innovations extend the horizons of QKD, not only addressing security concerns but also pushing the boundaries of achievable secure key rates, bolstering its position as a next-generation QKD paradigm.
A series of experiments has showcased significant advancements in quantum communication technology. Notably, the Modified BB84 protocol achieved a distance of 421 km over lab fiber in 2018. The Twin-field protocol demonstrated remarkable progress, achieving distances of 90.8 dB at 0.045 (2019), 502 km at 0.118 (2020), 509 km at 0.269 (2020), 605 km at 0.97 (2021), and covering 511 km at 3.45 in a field trial (2021). In lab fiber environments, the Twin-field protocol reached distances of 658 km at 0.092 (2022) and an impressive 830 km at 0.014 (2022), showcasing its rapid development. These accomplishments underscore the feasibility and growing effectiveness of quantum communication technologies, hinting at secure long-distance quantum communication becoming a reality.
Note: This article is a part of my Womanium Online Quantum Media Project. Find out about it here .
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