Playing games with wave functions

On Tuesday, a Canadian company chose an unusual setting to announce a new computer system – the Computer History Museum in Mountain View. (Home to thousands of unsuccessful machines made by now defunct companies). There D-Wave Systems demonstrated their 16 qubit quantum computing device, remotely located in Burnaby, BC. You can’t do much with 16 qubits, other than solving Sudoku puzzles. But D-Wave claims they can scale up their device to 1000 qubits or more.

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. “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.”

Well, that and raise a bunch of venture funding too, of course.

D-Wave quantum computer - Scientific American

Apparently, D-Wave is specifically targeting NP-complete problems. My buddy Steve Leibson has some more technical details:

Briefly, D-Wave’s Orion solves such problems by holding all possible solutions in a superposed state in a 16-qubit register, arranged in a ring on the 5×5 mm chip. A qubit is a quantum storage element that can hold a 0 or 1 (like a digital bit) and an infinite number of intermediate states, all in simultaneous superposition. The qubit’s operation depends on the physics of quantum mechanics and, consequently, Orion operates at 4 mK (that’s 4 thousandths of a Kelvin above absolute zero).

Orion accepts queries phrased in the common and familiar SQL (structured query language). […] D-Wave’s Orion determines the answer to such problems by creating “graphs” of problem solutions, superimposing all such graphs onto Orion’s 16-qubit storage register, and then searching all answers in parallel to find the solution with the lowest energy, which is the right answer based on the graph constructions.

It’s an impressive technical achievement, and I wish them good luck scaling up their machine. But to me this just seems like an expensive version of the old Spaghetti Computer.