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First "Commercial" Quantum Computer Solves Sudoku Puzzles

Quantum computing company banks on a long-shot form of quantum computing
D-Wave quantum computer



© J. CHUNG/D-WAVE SYSTEMS, INC.
A Canadian firm today unveiled what it called "the world's first commercially viable quantum computer." D-Wave Systems, Inc., "The Quantum Computing Company," during a much ballyhooed rollout at the Computer History Museum in Mountain View, Calif., hailed the new device as a big step toward the age of quantum computing, decades earlier than scheduled.

But experts say the announcement may be a bit—er—premature. Even if the computer were to work as advertised, it still would be nearly 1,000 times too small to solve problems that stump ordinary computers. Moreover, researchers do not know whether it will work at bigger sizes.

"There are still a lot of ifs and maybes here," says quantum computing researcher Seth Lloyd of the Massachusetts Institute of Technology. But he credits D-Wave for its willingness to test the idea. "From the scientific perspective," he says, "what they're doing is very interesting."

A working quantum computer is the dream of every national security official and hacker on Earth. The bits inside existing computers constantly flip between 0 and 1 as they perform small steps such as "if 0, then 1." But quantum physics allows particles like atoms, electrons and photons to be in two places at once—meaning they can represent 0 and 1 simultaneously, allowing more complex calculations.

Researchers believe that by combining many of these quantum bits, or qubits, they will be able to perform certain tasks that are currently out of reach. Chief among them: the ability to swiftly crack encrypted communications.

D-Wave is pursuing a different method that is easier to implement but cannot break encryption schemes, although simulations suggest it could solve other problems extremely rapidly. In most prototype quantum computing systems, researchers hit atoms with lasers or use other means to excite particles into fuzzy quantum states. But in a technique called adiabatic quantum computing, researchers cool metal circuits into a superconducting state in which electrons flow freely, resulting in qubits. They then slowly vary a magnetic field, which lets the qubits gradually adjust to each other, sort of like people huddling in the cold. In 2005 German researchers built a three-qubit adiabatic quantum computer.

D-Wave announced that it has constructed a 16-bit version crafted from the superconducting element niobium [see image above]. "What we've built is really a systems-level proof of concept," says Geordie Rose, D-Wave's co-founder and chief technology officer. "We want to get people's imagination stimulated."

For the demonstration, he says D-Wave operators remotely controlled the quantum computer, housed in Burnaby, British Columbia, from a laptop in California. The quantum computer was given three problems to solve: searching for molecular structures that match a target molecule, creating a complicated seating plan, and filling in Sudoku puzzles.

Rose says D-Wave plans to submit its results for peer review at a major journal. He notes that experts will be given a chance to inspect the system, and that the company plans to make its prototype available online free of charge to stir interest. Users would enter a problem to be solved, and the device would send the solution from Canada.

And how exactly would users know that it was the quantum computer rather than a human or ordinary computer answering their queries? "There's really no way to convince a skeptic who's accessing the machine remotely," Rose admits. For now, D-Wave's device is slower than an inexpensive home computer, but Rose says a potentially faster 1,000-qubit version should be available by the end of next year.

Reality check: Lloyd says that a quantum computer would probably need thousands of qubits to solve puzzles that today's computers cannot. The big question, he says, is whether the adiabatic method's gradual adjustment of qubits would operate rapidly at that size. Researchers are skeptical of adiabatic quantum computers because "it sounds too good to be true," Lloyd says. "It's not yet known whether they work or not, so really it actually makes sense to go and build some and see what happens."

"It probably won't work but it's not quixotic," Lloyd says, noting that he hopes the company reaches thousands of qubits and publishes its results. "If it works then they can solve really hard problems and they'll be very much in demand," he says. But given the odds, he adds, "It's certainly not the kind of company I'd invest my money in."

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