On February 13, D-Wave Systems, a startup based in Burnaby, British Columbia, claimed to have demonstrated “the world’s first commercial quantum computer.”
At the Computer History Museum in Mountain View, CA, Geordie Rose, the company’s founder and chief technology officer, showed how the Orion computer could search for a protein in a database and find the closest match, discover the optimal seating arrangement for the guests at a wedding reception, and solve a Sudoku puzzle.
Quantum computing, first proposed by the physicists Paul Benioff and Richard Feynman in the early 1980s, works by exploiting the strange ambiguities of quantum mechanics. According to the laws of quantum mechanics, the state of a particle such as an electron can be undecided: it could be on or off, spinning up or down.
In a quantum computer, each quantum bit of information–or qubit–can therefore be unfixed, a mere probability; this in turn means that in some mysterious way, a qubit can have the value of one or zero simultaneously, a phenomenon called superposition. Two qubits can thus represent four different values (00, 01, 10, and 11 in binary notation); four qubits can represent sixteen values; and so on. In theory, a quantum computer could solve in less than a minute problems that it would take a classical computer millennia to solve.
To date, most quantum computers have been more or less successful science experiments. None have harnessed more than 12 qubits, and the problems the machines have solved have been trivial. Quantum computers have been complicated, finicky machines, employing delicate lasers, vacuum pumps, and other exotic machinery to shepherd their qubits.
D-Wave (which has raised $44 million from investors such as venture capital firm Draper Fisher Jurvetson) claims that it has succeeded in constructing a practical quantum computer by employing a simple design, derived from technologies already used to make standard computer chips. The company describes the Orion as a 16-qubit “adiabatic quantum computer,” built around a chip made from a metal called niobium which, when sufficiently cold, becomes a superconductor. Chilled in a bath of liquid helium to nearly −273 ºC, the electrons in the niobium superconductor form particles called Cooper pairs, which can occupy the same quantum state, thus permitting the Orion to compute quantum algorithms.
Herb Martin, D-Wave’s chief executive, says this uncomplicated design will allow the Orion to “scale” to a 512-qubit machine later this year and to a 1,024-qubit computer by the middle of 2008.
But computer scientists who specialize in quantum computing have been profoundly skeptical of D-Wave’s demonstration. D-Wave provided no evidence to back up its claims: it has released only the sketchiest details about the inner workings of Orion. What computer scientists do know does not impress them.
Scott Aaronson, a theoretical computer scientist at the Institute for Quantum Computing in Waterloo, Ontario, and the author of a much-read blog called Shtetl-Optimized, began the obloquies when he denounced the Orion for being as useful at solving problems as “a roast-beef sandwich.”
Of Geordie Rose’s claims to having built the first practical quantum computer, Aaronson wrote in an e-mail, “Whatever else D-Wave might or might not have done, this can be instantly rejected as hype. If by ‘practical’ he means able to solve practical problems faster than existing classical computers, then this is clearly false. If he means able to solve tiny demonstration problems, he’s been beaten by loads of people. So I can’t think of any interpretation under which he’s telling the truth.”