基于非最大纠缠态的双向量子通信协议

对基于非最大纠缠态的量子密码协议进行了研究，并提出了新的看法。协议中的双向传输方式与量子超密度编码相似，可以通过发送量子比特对中的一个粒子来传送一个两比特的密钥。协议的安全性是基于量子力学中非最大纠缠态之间不可能通过本地幺正变换而相互转化的。偷听者Eve可能确定传输的量子态并窃取密钥，但无法重新发送此量子态，合法的通信双方将侦探到偷听者的存在。此种协议也适用于量子安全直接通信。

Two-way Quantum Communication Protocol based on Non-maximally Entangled States

This paper proposes new idears for quantum cryptography with a nonmaximally entangled. In a two-way configuration similar to quantum super dense coding, a two-bit key can be distributed by one particle of the qubit pair, The security of our scheme is based on the quantum-mechanical impossibility of local unitary transformation between certain nonmaximally entangled states. Although an eavesdropper, Eve, can always identify the quantum state and intercept the key, it is impossible for her to resend the state and the legitimate parties Can inevitably detect her. Our protocol is also capable to quantum secure direct communication.