what is A 的 "unitary" 操作, with that, B can figure out what should be B 的操作, with that, information is transmitted and decoded from A to B;
经典方式 here is 小于光速, obviously.
and you cannot do any 量子通信 for human beings without that 经典方式 part, and in that sense, 量子通信 <=光速