Abstract
Quantum communication is an important branch of quantum technology. It can safely transmit private information between legitimate parties and its unconditional security is guaranteed by quantum physics. So far, deterministic secure quantum communication without entanglement usually transmits single photons in two-way quantum channels. We propose a deterministic secure quantum communication proposal, and it requires a one-way quantum channel and a classical channel. In our protocol, a sender encodes logical bits by using two conjugate bases consisting of the polarization and time-bin degrees of freedom of a photon and transmits it to a receiver over a quantum channel. Upon receiving this photon, the receiver measures it randomly in two bases and can decode the bit deterministically with the help of the sender. Any attack from eavesdroppers will be detected by the legitimate parties. Furthermore, this protocol can be implemented with linear-optic elements and single-photon detectors.
Highlights
State and probability of photons prepared by Eve
而 当 Eve 测量重发 n 个光子时, 她的测量重发过程不干 扰 Bob 测量结果的概率应为 1 − (3/4)n , 这一结果 与先前基于单光子四个非正交态传输的方案相同 [6], 其优势在于我们不存在选错基矢的情况, 每一个未 用于安全检测的单光子都可以生成一个密钥, 这表 明我们的方案具有确定性的特点
Summary
为此, 与 QKD 不同, QSDC 不需要提前生成密钥, 是直接利用量 子信道进行通信的. 起初, 因为 QSDC 和 DSQC 都可以确定性地实现 信息的传输, 人们并没有特别区分这两类方案 [23]. 利用图 1 光路, Alice 可以确定性地 编码逻辑比特 0 (|+t0⟩和 |Ht+⟩) 和逻辑比特 1 (|−t1⟩和|V t−⟩). 经过 PBS1 透 射后, 光子透过 PBS2, 经 SW3 反射后以量子态 |+t0⟩进入量子信道, 发送给接收方 Bob. 2) 当 Alice 控制 SW1 处于反射 R 状态时, 光 子经过 SW1 反射到达分束器 BS1, 并由 BS1 的两 个输出端口等概率幅的输出. 两路径经 SW2 合束后, 光子态 变为|Ht+⟩, 并透过 SW3 进入量子信道发送给 Bob. 这样, 在编码逻辑比特 0 时, Alice 利用光学元件可 以确定性地制备|+t0⟩ 或 |Ht+⟩两种量子态, 并通 过同一量子信道发送给 Bob. 在编码逻辑比特 1 时, 图 1 中半波片 HWP 的 光轴设置为水平方向 θ = π/4, 使得穿过它的光子 态 |Ht0⟩变为 |V t0⟩.
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