Security of two quantum cryptography protocols using the same four qubit states
Security of two quantum cryptography protocols using the same four qubit states
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DOI：
10.1103/physreva.72.032301
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发表时间：
2005-05
影响因子：
2.9
通讯作者：
C. Branciard;N. Gisin;B. Kraus;V. Scarani
中科院分区：
文献类型：
--
作者：
C. Branciard;N. Gisin;B. Kraus;V. Scarani
第一个量子密码协议由 Bennett 和 Brassard 于 1984 年提出（BB84），近年来得到了广泛的研究。该协议使用四种状态（更准确地说，两个互补碱基）来编码经典位。最近，人们注意到，通过使用相同的四种状态，但不同的信息编码，可以定义一种在实际实现中更稳健的协议，特别是当使用衰减激光脉冲代替单光子源时[V.斯卡拉尼等人，物理学。莱特牧师。 92, 057901 (2004)，简称SARG04协议]。我们对 SARG04 在两种不同的情况下进行了详细研究。在第一部分中，我们考虑使用单光子源的实现：我们得出错误率 $Q$ 的界限，以防止窃听者的所有可能的攻击。 SARG04 获得的下限和上限（分别为 $Q\ensuremath{\lesssim}10.95%$ 和 $Q\ensuremath{\gtrsim}14.9%$）接近于 BB84 获得的下限和上限（分别为 $Q\ensuremath{\lesssim}12.4%$ 和 $Q\ensuremath{\gtrsim}14.6%$）。在第二部分中，我们考虑由衰减激光组成的现实源，并通过允许 Alice 优化作为距离函数的平均光子数来改进之前的分析。研究发现，对于各种 Eve 攻击，SARG04 协议在密钥速率和最大可实现距离方面都比 BB84 表现更好。
The first quantum cryptography protocol, proposed by Bennett and Brassard in 1984 (BB84), has been widely studied in recent years. This protocol uses four states (more precisely, two complementary bases) for the encoding of the classical bit. Recently, it has been noticed that by using the same four states, but a different encoding of information, one can define a protocol which is more robust in practical implementations, specifically when attenuated laser pulses are used instead of single-photon sources [V. Scarani et al., Phys. Rev. Lett. 92, 057901 (2004), referred to as the SARG04 protocol]. We present a detailed study of SARG04 in two different regimes. In the first part, we consider an implementation with a single-photon source: we derive bounds on the error rate $Q$ for security against all possible attacks by the eavesdropper. The lower and the upper bound obtained for SARG04 ($Q\ensuremath{\lesssim}10.95%$ and $Q\ensuremath{\gtrsim}14.9%$, respectively) are close to those obtained for BB84 ($Q\ensuremath{\lesssim}12.4%$ and $Q\ensuremath{\gtrsim}14.6%$, respectively). In the second part, we consider a realistic source consisting of an attenuated laser and improve on previous analysis by allowing Alice to optimize the mean number of photons as a function of the distance. The SARG04 protocol is found to perform better than BB84, both in secret-key rate and in maximal achievable distance, for a wide class of Eve's attacks.