Namiki Ryo, Hirano Takuya
CREST Research Team for Photonic Quantum Information, Department of Physics, Gakushuin University, Mejiro 1-5-1, Toshima-ku, Tokyo 171-8588, Japan.
Phys Rev Lett. 2004 Mar 19;92(11):117901. doi: 10.1103/PhysRevLett.92.117901. Epub 2004 Mar 16.
In this Letter, first, we investigate the security of a continuous-variable quantum cryptographic scheme with a postselection process against individual beam splitting attack. It is shown that the scheme can be secure in the presence of the transmission loss owing to the postselection. Second, we provide a loss limit for continuous-variable quantum cryptography using coherent states taking into account excess Gaussian noise on quadrature distribution. Since the excess noise is reduced by the loss mechanism, a realistic intercept-resend attack which makes a Gaussian mixture of coherent states gives a loss limit in the presence of any excess Gaussian noise.
在本信函中，首先，我们研究了一种具有后选择过程的连续变量量子密码方案针对个体分束攻击的安全性。结果表明，由于后选择的存在，该方案在有传输损耗的情况下仍可保持安全。其次，我们考虑正交分布上的过量高斯噪声，给出了使用相干态的连续变量量子密码学的损耗极限。由于损耗机制会降低过量噪声，一种产生相干态高斯混合的现实的截获重发攻击在存在任何过量高斯噪声的情况下给出了一个损耗极限。
