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密码学中的state是什么意思( 四 )

云知道密码


光放大器的意思是如果你输入一个非常弱的信号
例如一个单光子
有时它会被放大，但有时不会被放大
所以你会得到一个与它一起输出的噪声光子
所以，光束会变得更亮
但是在分辨光子偏振上 ， 与原始未放大光子相比
亮光束不会更有用
因此没有办法解决这个不确定原则
——The end——
了解更多量子密码学
旧时代密码术和密码学圣杯 （上）冷战中的“一次一密”| Gilles Brassard
公钥密码术的原理、发展及其在量子时代的困境 （中） | Gilles Brassard
量子密码学的诞生及其战?。ㄏ拢﹟ Gilles Brassard
量子密码学的实现（上）爱因斯坦的困惑| Artur Ekert
量子密码学的实现（下）像物理学家一样思考| Artur Ekert
英文版
So I'm going to be talking about the relation of physics to mathematics also.
But what I'd like to do is take an area of mathematics or physics,
which is considered to be really hard to understand, worse than rocket science.
And give you some tools for understanding it
if you're not a technically minded person.
Or if you are a technically minded person,
some metaphors are ways of explaining it to the general public.
Because I think the non understanding of quantum physics,
which is now lies at the root of information and communication,
is a terrible thing to not understand.
It's one of the fundamental things about the universe that we live in
that everyone should understand, not just scientists.
And that means that we need to find the right ways of explaining it.
We're in the middle of an information revolution.
This revolution is based on some really brilliant abstractions by many people.
But we associate them with Turing,
who put the theory of computing into an abstract basis,that is
that you can think about computing is independent of the notion of thehardware.
There is a universal notion of computing.
There is a universal computer that can simulate any other computer.
And Shannon,
who did something even more revolutionary,
that is to think about communication in an entirely mathematical way.
That is that there is a theory of communication.
that is independent of the meaning of the message.
Now,even today, if you try to say to a person on the street,
"I want to tell you about communication without telling you about meaning."
they would think you were a little crazy.
And yet that's what leads to the information revolution we had today.
But the information carriers, Turing and Shannon thought about, were viewed
as what a physicist would call a classical system.
And that is that their statesare in principle reliably distinguishable,
and are not disturbed by measuring them.
Youcan make a copy of information.
In fact, you can do it very easily.
And the only kind of trouble you can get into is a typically legal trouble.
Tospecify the joint state of two things,
it's necessary and sufficient to say the state of each one.
That almost goes without saying.
Well,anyway, physicists and chemists have known for a long time,
that atoms and small particles like atoms andphotons don't really behave that way.
But that was a matter of interest, really only for physicists and chemists.
And now we know that these last properties here
are important not only for physics and chemistry,
butfor understanding what information and communication are all about.
In other words, what Shannon and Turing should be thinking about.
Nowadays,everybody understands classical information,
cause we use it all the time.
If you go to a computer store and you say,
"Do you have that program for my mac?"
You're in principle, using the idea of Turing and there is a universal computer.

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