Programmable Quantum Computer Created

An anonymous reader writes "A team at NIST (the National Institute of Standards and Technology) used berylium ions, lasers and electrodes to develop a quantum system that performed 160 randomly chosen routines. Other quantum systems to date have only been able to perform single, prescribed tasks. Other researchers say the system could be scaled up. 'The researchers ran each program 900 times. On average, the quantum computer operated accurately 79 percent of the time, the team reported in their paper.'"

Comments

Re:correct and incorrect?

[NoYob]

So is that 21% of the time is was both correct and incorrect ?

That's correct and the other 79% of the time the cat died.

In Some Alternate Universe

[WED Fan]

In some alternate universe, there's a guy who is riding a bus, a thought pops into his head, "Pick a number between 1 and 100. Now, add 3. Now, divide by 13...". 99% of the time, he does the problem in his head, 79% of the time he finishes it. 1% of the time, he says, "Screw it". 100% of the time, he wonders where the hell these things are coming from and decides to check himself into the nearest mental ward.

Quantum computing is screwing up someone's day.

Re:79% accuracy ...

[Timothy Brownawell]

79% accurate. That's pretty useless.

Not useless at all, just have it solve the same problem 5 or 15 times and go with the answer that it gives most often. Plus, for some problems it's much easier to verify an answer than to come up with it -- for those problems, just pair it with a normal computer to check the answers, and keep trying until it says the answer is right.

Re:How do they know?

[palegray.net]

I suppose I could read the paper.

I think you might be on to something here.

Re:79% accuracy ...

[Jahava]

That's TOTALLY moronic. That's like saying "get 5 or 15 people to guess your birthday and go with the answer that it gives most often."

Are people accurate 79% of the time? In the examples you gave? Then no, it's not like that at all.

How stupid can you get?

Many thanks for demonstrating!

Re:79% accuracy ...

[chhamilton]

No, it's actually a perfectly reasonable idea. Consider running the device (n+m) times. The probability of it being right n times and wrong m times is given by:

P(n,m) = (n+m)!/n!/m! 0.79^n 0.21^m

Now consider the probability of it being right (majority has the right answer) out of 2n+1 trials. This is the given by:

S(n) = sum( P(n+1+i,n-i), i=0..n )

This can be simplied to a closed form using Legendre and gamma functions, but that's kind of messy and it's far easier to just plug in values and do the summation. As it turns out, doing the experiment 15 times and taking the majority (plugging 7 into S(n)) will give you the correct answer 99.4% of the time. Doing things 35 times gets you to five nines of accuracy... completely reasonable in my books.

First infinite loop....

[Temujin_12]

do {
    solveProblem();
} until (getPhotonPosition() && getPhotonVelocity());