The line is the world's first trunk line for secure quantum telecommunications.

这条线是世界上第一条保证量子通讯的中继线。

It's a story that begins over 150 years ago in 1863, when the world's first underground line opened, the Metropolitan Railway.

这要从 150 多年前的 1863 年开始说起，那年，大都会铁路开通了世界上第一条地铁。