Alice Eve

If Eve intercepts Bob's pulses and changes the separation between them, she can trick Alice into sending photons that have slightly different polarisations from those that were intended.

如果伊娃能够截取鲍勃方发送的这两道脉冲，并改变其间距，就可以诱使爱丽丝方发送出与原计划略有不同的极性光子。

By comparing a subset of the photons that Alice sends with what Bob measures, the pair can check for the presence of errors introduced by Eve.

通过与爱丽丝发送给鲍勃的光子子集进行比对，双方就可以发现在传输过程中出现了错误，伊娃也就暴露出来了。