Explain Quantum Cryptography to me like you would a 4 year old child

Number_25

Number_25

Number_25

Soldato
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23 Dec 2010
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Hey there,

Revising for tomorrows exam, I'm still not understanding Quantum Cryptography.

I need to know what happens on a step by step basis.

If anyone can help me I'd be forever thankful.

Thanks
 
If you understand normal crypt, you shouldnt have too much of a problem. I suggest going back to basics with that. Unless of course your going in deep quantum but then i imagine it's something you would already know?
 
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Just reading up on it. Seems that the problem in traditional cryptography is the 'Key distribution problem' when using a secret key to encode/decode. Two people can't pass the information between them about the secert key they will be using, without having to have a secret key again to pass this info. So in essence it's a catch 22. This is where the quantum cryptography comes in. They uses the unique properties of photons spin to transmit the secret key.

The foundation of quantum physics is the unpredictability factor. This unpredictability is pretty much defined by Heisenberg's Uncertainty Principle. This principle says, essentially, that it's impossible to know both an object's position and velocity -- at the same time.But when dealing with photons for encryption, Heisenberg's principle can be used to our advantage. To create a photon, quantum cryptographers use LEDs -- light emitting diodes, a source of unpolarized light. LEDs are capable of creating just one photon at a time, which is how a string of photons can be created, rather than a wild burst. Through the use of polarization filters, we can force the photon to take one state or another -- or polarize it. If we use a vertical polarizing filter situated beyond a LED, we can polarize the photons that emerge: The photons that aren't absorbed will emerge on the other side with a vertical spin ( | ).The thing about photons is that once they're polarized, they can't be accurately measured again, except by a filter like the one that initially produced their current spin. So if a photon with a vertical spin is measured through a diagonal filter, either the photon won't pass through the filter or the filter will affect the photon's behavior, causing it to take a diagonal spin. In this sense, the information on the photon's original polarization is lost, and so, too, is any information attached to the photon's spin.

So how do you attach information to a photon's spin? That's the essence of quantum cryptography. Read the next page to find out how quantum cryptography works.
Click to expand...

I didn't finish last couple of pages though.

http://science.howstuffworks.com/science-vs-myth/everyday-myths/quantum-cryptology4.htm
 
dfarrall said:
If you understand normal crypt, you shouldnt have too much of a problem. I suggest going back to basics with that. Unless of course your going in deep quantum but then i imagine it's something you would already know?
Click to expand...

Understands quantum cryptography, doesn't understand the difference between "your" and "you're" or how to use apostrophes = mind blown!

:D :p

(I hope you take it in the joking way it was intended)
 
Basically it comes down to if you know the value of something local you know the value of something remote with absolute certainty because they are entangled. So you know the remote thing is legit because its integrity is literally backed by pure physics.
 
If you have a '1' photon you know the other photon is a '0' with 100% certainty even if nobody has checked it. Once one side of the entanglement is collapsed from super position the othed side is also known without having to be observed because it can only be the opposite. It's actually a lot simplier than people think.

Search youtube for quantum conspiracy google talk.
 
It went ok, thanks for asking.

They gave us a choice of 4 questions to answer in the second section of the exam - so I chose Robotics, Chaos and Networks. I wasn't able to answer anymore because of the strict time constraints. - I think I got over 60% though, which is good by my standards.
 
I filmed a lecture at Bristol University on Quantum Mechanics a few weeks ago, part of which was on this (the lecturer is devising systems for it I think).

Interesting stuff!
 
You realise that the word 'Quantum' is the go to word to cover for the fact that people know it works but don't know why.

Examples:

Quantum Tunnelling: Magically travelling through a solid substance

Quantum Entanglement: Magically connecting two particles across space, ignoring the speed of light.

Quantum Cryptography: Magically encrypting stuff.

Therefore quantum is magic and the people teaching you don't know what it is so you have no hope.

Good luck with the exam :)
 
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