标题： 基于最优量子克隆的实验窃听 显示英文标题

标题： Experimental Eavesdropping Based on Optimal Quantum Cloning

摘要： 量子密码学的安全性由不可克隆定理保证，这意味着窃听者在未知状态下复制传输的量子比特会导致其扰动。 然而，在实际密码系统中，必须允许一定水平的扰动，例如覆盖传输损耗。 窃听者可以通过将噪声信道替换为更好的信道，并对传输的量子比特进行近似克隆来攻击此类系统，这些克隆会引发扰动，但低于合法用户假设的噪声水平。 我们通过使用最近开发的光子多功能量子克隆器 [K. Lemr 等，Phys. Rev. A 85, 050307(R) (2012)] 准备的两态探测器，实验上展示了对 Bennett 和 Brassard (BB84) 的量子密钥分发协议以及 Renes (R04) 的三态球面编码的对称个体窃听。 我们证明了我们的高成功率克隆装置使得窃听成为可能，因为它隐藏在正常的传输损耗中。 我们认为这个实验可以激发对量子克隆其他操作应用的研究。 显示英文摘要

摘要： The security of quantum cryptography is guaranteed by the no-cloning theorem, which implies that an eavesdropper copying transmitted qubits in unknown states causes their disturbance. Nevertheless, in real cryptographic systems some level of disturbance has to be allowed to cover, e.g., transmission losses. An eavesdropper can attack such systems by replacing a noisy channel by a better one and by performing approximate cloning of transmitted qubits which disturb them but below the noise level assumed by legitimate users. We experimentally demonstrate such symmetric individual eavesdropping on the quantum key distribution protocols of Bennett and Brassard (BB84) and the trine-state spherical code of Renes (R04) with two-level probes prepared using a recently developed photonic multifunctional quantum cloner [K. Lemr et al., Phys. Rev. A 85, 050307(R) (2012)]. We demonstrated that our optimal cloning device with high-success rate makes the eavesdropping possible by hiding it in usual transmission losses. We believe that this experiment can stimulate the quest for other operational applications of quantum cloning.