Can quantum algorithms be useful?
Has any one been successful in putting quantum algorithms to any use?
A:
There is also some research into whether quantum computing can be used to solve hard problems, such as factoring large numbers (if this was feasible it would break current encryption techniques).
frankodwyer
2009-01-01 12:52:12
+2
A:
My understanding is that current quantum computing capabilities can be used to exchange keys securely. The exchanged keys can then be used to perform traditional cryptography.
Darron
2009-01-01 14:15:36
What you have in mind is quantum cryptography, but it uses quantum physics directly ("physically"), and does not use / relate to quantum computing.
ShreevatsaR
2010-08-15 00:52:01
+4
A:
The only logical answer is that they are both useful and not useful. ;-)
Gamecat
2009-01-01 14:57:31
+3
A:
"Quantum algorithms" are algorithms to be run on quantum computers.
There are things that can be done quickly in the quantum computation model that are not known (or believed) to be possible with classical computation: Discrete logarithm and Integer factorisation (see Shor's algorithm) are in BQP, but not believed to be in P (or BPP). Thus when/if a quantum computer is built, it is known that it can break RSA and most current cryptography.
However,
- quantum computers cannot (are not believed to, I mean) solve NP-complete problems in polynomial time, and more importantly,
- no one has built a quantum computer yet, and it is not even clear if it will be possible to build one -- avoiding decoherence, etc. (There have been claims of quantum computers with a limited number of qubits -- 5 to 10, but clearly they are not useful for anything much.)
"Well, there's a quantum computer that can factor 15, so those of you using 4-bit RSA should worry." -- Bruce Schneier
[There is also the idea of quantum cryptography, which is cryptography over a quantum channel, and is something quite different from quantum computation.]
ShreevatsaR
2009-01-01 18:49:10
BTW, I should repeat: [quantum cryptography](http://en.wikipedia.org/wiki/Quantum_cryptography) is something else entirely, which has nothing to do with quantum algorithms or quantum computation. It involves using quantum physics to set up a **physically** secure channel to share keys.
ShreevatsaR
2010-08-15 00:50:37
A:
Stackoverflow runs on a quantum computer of sorts.
Feynman has implied the possibility that quantum probability is the source of human creativity.
Individuals in the crowd present answers and vote on them with only a probability of being correct. Only by sampling the crowd many times can the probability be raised to a confident level.
So maybe Stackoverflow examplifies a successful quantum algorithm implementation.
What do you think?
jeffD
2009-03-13 03:59:49