GOOGLE IS UPGRADING its quantum computer. Known as the D-Wave, Google’s machine is making the leap from 512 qubits—the fundamental building block of a quantum computer—to more than a 1000 qubits. And according to the company that built the system, this leap doesn’t require a significant increase in power, something that could augur well for the progress of quantum machines.

Together with NASA and the Universities Space Research Association, or USRA, Google operates its quantum machine at the NASA Ames Research center not far from its Mountain View, California headquarters. Today, D-Wave Systems, the Canadian company that built the machine, said it has agreed to provide regular upgrades to the system—keeping it “state-of-the-art”—for the next seven years. Colin Williams, director of business development and strategic partnerships for D-Wave, calls this “the biggest deal in the company’s history.” The system is also used by defense giant Lockheed Martin, among others.

Though the D-Wave machine is less powerful than many scientists hope quantum computers will one day be, the leap to 1000 qubits represents an exponential improvement in what the machine is capable of. What is it capable of? Google and its partners are still trying to figure that out. But Google has said it’s confident there are situations where the D-Wave can outperform today’s non-quantum machines, and scientists at the University of Southern California have published research suggesting that the D-Wave exhibits behavior beyond classical physics.

Over the life of Google’s contract, if all goes according to plan, the performance of the system will continue to improve. But there’s another characteristic to consider. Williams says that as D-Wave expands the number of qubits, the amount of power needed to operate the system stays roughly the same. “We can increase performance with constant power consumption,” he says. At a time when today’s computer chip makers are struggling to get more performance out of the same power envelope, the D-Wave goes against the trend.

### The Qubit

A quantum computer operates according to the principles of quantum mechanics, the physics of very small things, such as electrons and photons. In a classical computer, a transistor stores a single “bit” of information. If the transistor is “on,” it holds a 1, and if it’s “off,” it holds a 0. But in quantum computer, thanks to what’s called the superposition principle, information is held in a quantum system that can exist in two states *at the same time*. This “qubit” can store a 0 and 1 simultaneously.

Two qubits, then, can hold four values at any given time (00, 01, 10, and 11). And as you keep increasing the number of qubits, you exponentially increase the power of the system. The problem is that building a qubit is a extreme difficult thing. If you read information from a quantum system, it “decoheres.” Basically, it turns into a classical bit that houses only a single value.

D-Wave believes it has found a way around this problem. It released its first machine, spanning 16 qubits, in 2007. Together with NASA, Google started testing the machine when it reached 512 qubits a few years back. Each qubit, D-Wave says, is a superconducting circuit—a tiny loop of flowing current—and these circuits are dropped to extremely low temperatures so that the current flows in both directions at once. The machine then performs calculations using algorithms that, in essence, determine the probability that a collection of circuits will emerge in a particular pattern when the temperature is raised.

By CADE METZ

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Source: Google’s Quantum Computer Just Got a Big Upgrade | WIRED