Modified BB84 quantum key distribution protocol robust to source imperfections

The Bennett-Brassard 1984 (BB84) protocol is the most widely implemented quantum key distribution (QKD) scheme. However, despite enormous theoretical and experimental efforts in past decades, security of this with imperfect sources has not yet been rigorously established. In paper, we address shortcoming prove BB84 presence multiple source imperfections, including state preparation flaws side channels, such as Trojan-horse attacks, mode dependencies classical correlations between emitted pulses. To do so, consider a modified that exploits basis mismatched events, which are often discarded standard analyses scheme; employ reference technique, powerful mathematical tool to accommodate imperfections analysis QKD. Moreover, compare achievable secret-key rate three-state loss-tolerant protocol, show addition fourth state, while redundant ideal conditions, significantly improves estimation leaked information resulting better performance. This paper demonstrates relevance guaranteeing implementation security, taking us step further towards closing existing gap theory practice