One time pad is
information-technically secure as far as I remember. It was the situation that if you eliminate the potential of human errors and such, you can prove mathematically that the OTP cannot be broken.
Here the situation is actually similar. I won't go into a lot of detail due to the complexity of quantum mechanics (more information on how this works can be found here:
http://evilzone.org/science/10-science-facts-per-day!/msg54856/#msg54856), but basically the idea is as follows:
A quantum computer uses the principle of quantum entanglement. This process is something that scientists are very successful in replicating, and we've established impressive records with this.
Quantum entanglement works as such: two particles separated by space can be "linked" together by a laser. When they become linked, or "entangled", any amount of space you put between them will not break this link.
Each particle has a property called "spin" which can be of two types: up and down. Down is 0, up is 1. The link makes sure that if I "poke" one of the particles and make it spin UP, it's entangled partner will INSTANTLY switch to a DOWN spin.
What does this mean? Well this is wireless communication. Imagine the following scenario: 10 particles on Earth are entangled with 10 particles on a spaceship. If I have the Earth particles as 0000000000, their entangled counterparts will have values of 1111111111. A simple quantum NOT-gate will insure a similar value for the qubits (quantum bits).
Now, if I modify my initial state of qubits to, lets say 0100011111, this state will be INSTANTLY (it's been measured that the speed of quantum entanglement is
at least 100.000 faster than the speed of light) transmitted to the spaceship.
Why is this so secure you ask? Well the mechanism that quantum entanglement functions on is completely unknown. Speculation has been made by top scientists, but we're no closer to answering the question until we figure out the basic elements that everything is made of.
Basically this means we need to prove M-theory (most likely candidate so far) before even attempting to figure out how quantum entanglement works.
Given the above info, the simple deduction can be made that there is no way to intercept the communication. It's amazing to think about it, but it's almost as if the entangled particles are not two different entities, but rather just opposites of the same particle (i.e. one is the North of a magnet, one is the South of a magnet. Opposed but the same) which exist in two places at the same time.
No interception of the signal = no possibility to find info, crack info or modify info.
HOWEVER, it might be theoretically possible to entangle your own quantum computer with one of the other two! So in that case you would be receiving information as well. That's a problem, but it's been basically solved. All we need is a fully working quantum computer to test it out (quote taken from Wikipedia, and the names of the tech are links, so you can click on 'em):
Currently post-quantum cryptography is mostly focused on four different approaches:
This was created by means of the PQCrypto conferences which started in 2006 and inspired many scientists to create algorithms that do not rely on mathematical phenomena in order to create security (i.e. RSA and modular arithmetic) but rather rely on the laws of physics in order to create a system that
literally cannot be broken - as that would mean breaking a law of physics.