Quantum machines on the way

[Frodo42]

I just read this post from SlashDot (http://it.slashdot.org/it/05/01/20/0358215.shtml?tid=172&tid=126) saying that forms of quantum machines are starting to emerge made for factorizations of big numbers.

I saw a short one hour presentation from one of the physics-professors working with quantum computers at Aarhus University (where I study), so my knowledge is not to big on this. However in that lecture he presented us to an breaktrough that was about namely factorisation of numbers (at that stage some years ago they had gotten 1 digit numbers correct factorized, they were still fighting 2 digit numbers).

Now that there appearently is coming commercial machines on the market, will we be able to use them for projects like SoB and what will that mean?

[kugano]

Extremely premature to even think about this. "General-purpose" quantum computers (i.e. capable of running something as complex as a DC client) won't be available to the general public for a very, very long time.

However, when the time comes, yes, quantum factoring would be good news for computational number theory, including SB. I just hope I live long enough to see it.

[Vato]

It may well kill public key cryptography in it's current form as well...

[Keroberts1]

well theoretically quantum computation is almost limitless in its power so just by brute force almost all cryptography could be broken.

[Booj]

Quantum cryptology is a much more mature field than quantum computing. It's starting to see commercial applications because the technology exists. Quantum computers however, still have many hurdles to overcome. The largest number factored by a quantum computer so far is, I believe, 15. That is the current state of things and it will be many years before 128 bit and larger numbers can be factored.

SOB should (hopefully) be completed before we see any quantum computers (if ever) that can lend a hand to this effort.

Quantum computing is an exciting field, but the promised land is still a long way off.

[vjs]

Sounds like "Timeline" to me...

[Keroberts1]

yes but the important thing to remember is that when there is a demand for something humans tend to make it happen. Since regular processors are beginning to reach their limits i believe that quantum computers will be given alot more development energy very soon. We'l probably see one within ten years. Therefore even though it is possible that our project will still be running for long after that the idea of having to work with N sizes of billions and more is seeming less stressing.

[cjohnsto]

One thing to remember is that quantum machines are exponentially better for searches but they will probably not be better, but infact a lot worse for the most common computing tasks. As most computing tasks require sequential calculations not searches.

For interest:
I believe that Dixon's algorithm is what is actually used on quantum computers for factoring, Dixon's can also be run on classical computers but is not very efficient compared to GNFS.

From my understanding (very limited) Dixon's algorithm has a bottle neck which is solved by quantum computers i.e. the bottleneck changes from O(n^3) to O(n^2) or something like that when implemented on a quantum computer.

It is important to remember however that in big Oh notation the hidden terms can be killers.

[tqft]

If you wanted a ten fold improvement in computing power right now - fix thecrap software we live with.

Nanotech (another of those things coming) biggest problem will not be the materials science or designin stuff but writing software that will keep what you make working properly. Sure some nanotech is just about new materials, but any type of organised molecular machine system will require awesome software skills. We have had multiple processor systems for years and still there are large arguments over basic design and holes in our theoretical knowledge of what they can do.

Quantum computing takes these problems to a whole new level. People haven't only just begun to envisage how they should think about the problem.

[Booj]

For factorisation, quatum computers use Shor's algorithm, which is designed specifically for quantum computers (ie, can't be done without them, well it can be simulated but that's not the point). There are still theoretical boundaries to overcome to see if quantum computers of larger bit numbers (~10+) are physically feasable. They have huge problems dealing with decoherence (fancy quantum word for stability).

[cjohnsto]

quatum computers use Shor's algorithm,

My mistake.:blush: