Quantum Computers Are Still No Faster Than Your Average PC

Illustration for article titled Quantum Computers Are Still No Faster Than Your Average PC

The D-Wave 2 is a much-hyped quantum computer, but, as scientists now report, it's not actually any faster than a regular old PC. Wait, didn't we say it was 3,600 times faster just a few months ago? Yes, and both are right. Whether one computer is faster than another is actually a mighty complicated question.

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Quantum computers can, theoretically, be faster because they take advantage of a quirk in quantum mechanics. While classical computers use bits in 0 or 1, quantum computers use "qubits" that can exist in 0, 1 or a superposition of 2, which allows it to work through possible solutions more quickly.

The D-Wave 2 is the second commercially available quantum computer—"commercially available" if you have something like $15 million lying around. Lockheed Martin bought one that is now housed at the University of Southern California, where the current study was performed, for example, and Google bought one too.

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So why are there different numbers flying around about the speed of the D-Wave 2? Well, it depends on how you test it. D-Wave 2 was 3,600 times faster when it was solving a problem it was specifically designed to solve. To make a crude analogy, it's like comparing hammers and screwdrivers when you're trying to hammer a nail. But in a study published today in Science, a matchup ran optimized algorithms on the PC, ensuring a more even playing ground. The computer scientists found no evidence of "quantum speedup."

But that doesn't mean quantum computing is a dead end. New Scientist aptly explains why this particular test may be underestimating D-Wave's abilities:

D-Wave computers solve problems in a process similar to exploring a hilly landscape where the lowest points corresponds to the best solution. While an ordinary computer is forced to climb up and over the hills to find the low points, a quantum machine can simply tunnel its way through.

The trouble is that many test problems aren't challenging enough, leading some to suggest that the reason D-Wave didn't show a quantum speed-up in some tests...isn't because it is not able to deliver a better performance, but rather because the test didn't force it too.

There's something humbling about the fact that we've created a computer whose abilities we don't really even how to test yet. [Science via Wired, New Scientist]

Top image: D-Wave

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DISCUSSION

Quantum computers aren't just faster versions of regular computers. They're totally different animals. They're way, way faster as some things (notable examples include factoring large integers and searching unsorted databases) and way worse at other things (you wouldn't want to use one for arithmetic) because their internal workings are based on disparate branches of science. Saying that one is "faster" than the other is like saying that a car is better transportation than your feet. They're not comparable in their operations and they're optimized for completely different things.

The point of quantum computers is that they can be used in tandem with classical computers in a way that takes advantage of the strengths of both. That's what is going on with the D-Wave, and that's why we're researching them. We can keep all of our computer science and add some awesome new possibilities.