Modeling Alignment Error in Quantum Key Distribution Based on a Weak Coherent Source
Guan‐Jie Fan‐Yuan, Shuang Wang, Zhen−Qiang Yin, Wei Chen, De‐Yong He, Zheng‐Fu Han, Guang‐Can Guo · Physical Review Applied · 2019
In optical quantum cryptography, alignment error is important in secure key generation for quantum key distribution (QKD), being one of the roots of error events. However, theoretical modeling typically only reflects the behavior of a single photon, which is incompatible with a weak coherent source. This study develops a realistic model to include the propagation of multiphoton pulses in the misalignment-error analysis by defining the $l\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}k\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}e$ $l\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}h\phantom{\rule{0}{0ex}}t$ $r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$, which can be obtained conveniently in practical QKD systems. In addition, double-click events can be depicted precisely, and thus the gap between the model and real systems is narrowed.