论文标题
评论“量子密钥协议协议”
Comment on "Quantum key agreement protocol"
论文作者
论文摘要
Zhou等人提出了基于量子传送的前两个方量子密钥协议（QKA）方案。 （电子信函40.18（2004）：1149-1150）。在此协议中，为了获得钥匙位字符串，一个各方使用设备获得两个量子状态的内部产品，一个是未知的，另一个则执行铃铛测量。但是，在本文中，我们表明，即使只有一个量子位是未知的，也无法获得将输出两个Qubit的内部产物的设备。之所以如此，是因为这种设备的存在将暗示在二维矢量空间中的四个不同状态中完全区分。这在量子力学中不允许。此外，我们认为这种设备的存在也将暗示违反“无信号定理”。最后，我们还评论说，该协议根本不是一个有效的密钥协议协议。
The first two party Quantum Key Agreement (QKA) protocol, based on quantum teleportation, was proposed by Zhou et al. (Electronics Letters 40.18 (2004): 1149-1150). In this protocol, to obtain the key bit string, one of the parties use a device to obtain inner product of two quantum states, one being unknown, and the other one performs Bell measurement. However, in this article, we show that it is not possible to obtain a device that would output the inner product of two qubits even when only one of the qubit is unknown. This is so because existence of such device would imply perfectly distinguishing among four different states in a two-dimensional vector space. This is not permissible in quantum mechanics. Furthermore, we argue that existence of such a device would also imply violation of the "No Signalling Theorem" as well. Finally, we also comment that this protocol is not a valid key agreement protocol at all.
