#科普#量子物理(16)

in steempress •  2 months ago  (edited)

量子密码学

密码用上量子物理所拥有的特性会很安全。有很多关于量子密码的协议,以原始的BB84协议3和E91协议4来作为例子。 

BB84协议的BB来自于Charles Bennett and Gilles Brassard的这2人的姓氏的首字母。它运用了波函数的叠加和塌缩原理,这在之前说过的——观测会改变量子状态。

比如我给你发一条消息,为了不让其他人看见我将消息存储到量子粒子上,一旦其他人截取了这条消息,那么这条消息被观测到就会改变粒子状态,原始编码也就被破坏了。

当你拿到被其他人截取过的密钥时,就会发现有人已经看过了,这样消息被其他人知道的事也就暴露了。而我们要做的就是放弃这组密钥,发送新的。  

E91协议运用的是量子物理的另一个原理——量子纠缠态。

同样可以利用爱波罗悖论来复制量子隐形传送,将密钥通过量子隐形传送到你的手上,是直接“出现”,中间过程没有渠道,也就截取不到。

听起来这种方式很奇幻,但现在己经有这样的服务了,2007年瑞士大选就是用量子加密模式来保证投票安全的。

 “斯科提,把我传送上去!”量子的隐形传送其实己经实现了。 1993年,量子隐形传送的理论基础被一个研究团队提出。四年后,有研究团队首次实现了光子的隐形传送。 

《星际迷航》中有专门的设备扫描将要被传送的物体,好在目的地重塑它。其实,量子隐形传送和电视里看到的有所不同。 

海森堡的不确定原理说,电子的位置和速度是无法同事被准确的测量的,因此,我们无法精确的扫描一个人或一样东西,在另外的一个地方重塑它们。量子隐形传送利用量子纠缠态来避免了这个问题。 

举个例子:我在地球要传送一个东西(几个原子)到空间站,将这个东西放在粒子拼盘里,这些粒子和空间站的粒子拼盘处于纠缠态。在特定时刻,空间站里的粒子会还原为初始对象,这样量子隐形传送实现。 

可是,我们传送的是量子态(信息)还是物体本身呢? 注意量子隐形传送不是量子复印机,量子力学中有一个定理是**不可克隆**定理,禁止对什么什么进行完全复制。 虽然人类的隐形传送还是停留在科幻想象中,但己经运用在信息加密中了,请等待进一步发展~



Posted from my blog with SteemPress : http://cocozl.cn/2019/12/26/%e7%a7%91%e6%99%ae%e9%87%8f%e5%ad%90%e7%89%a9%e7%90%86%ef%bc%8816%ef%bc%89/
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