Quantum computers could one day perform calculations beyond the reach of even the most powerful classical supercomputer, but for now building and maintaining these machines remains immensely expensive and difficult.

So over the past few years, the nascent industry has begun to make some of the relatively few quantum machines in existence available to researchers and businesses via the computing cloud.

A startup called Rigetti Computing has just taken the wraps off a new Quantum Cloud Service (QCS) that builds on its existing offering, which includes Forest, a software toolkit for quantum programming in the cloud. There’s a $1 million prize for the first person or team using QCS to demonstrate that a quantum machine is capable of showing what the company calls "quantum advantage".

Rigetti defines this as showing that a quantum machine can come up with a higher quality, faster, or cheaper solution to an important and valuable problem than a classical one can. (Rigetti says details of the competition will be unveiled on October 30.)

The company also recently unveiled the world’s most powerful quantum processor, a 128-qubit model that tops the previous record holder, Google’s 72-qubit Bristlecone chip (see the MIT Technology Review qubit counter). QCS users will initially be limited to a 16-qubit chip, however. The service will also be limited to certain customers and partners of Rigetti at first, before becoming more widely available later this year.

The reason there’s so much excitement around quantum computing is that unlike traditional machines, which use standard digital bits that can represent either 1 or 0, qubits can be both at the same time. Adding just a few extra qubits to a machine—and linking them via a phenomenon known as “entanglement”—creates exponential leaps in computing power (see “Serious quantum computers are finally here. What are we going to do with them?”).

As the technology develops, quantum computing could lead to significant advances in numerous fields, from chemistry and materials science to nuclear physics and machine learning.

Speed trap

Thomas Papenbrock, a nuclear physicist at the University of Tennessee, has used both IBM’s and Rigetti’s cloud services to compute the binding energy of the deuteron, a particle consisting of a proton and neutron that forms the center of the deuterium (or heavy hydrogen) atom. Although it’s possible to do this with classical computers, Papenbrock says he’s keen to use quantum machines through the cloud in order to learn more about their potential.

To run such experiments, researchers often program their own classical computers with hybrid quantum algorithms that then use application programming interfaces, or APIs, to call on quantum machines in the cloud for specific bits of a calculation. The results are then shipped back to the classical machines.

Rigetti says its own team, and users of its existing cloud service, found that this approach created latency issues, slowing down algorithms’ performance.

QCS tackles the problem with a data center containing both quantum computers and classical ones in a system optimized to run entire hybrid algorithms. The firm says that over the next few months, quantum algorithms will run 20 to 50 times faster on its QCS than on its current cloud setup, and significantly faster beyond that.

The service also comes pre-configured with Forest and other tools to make it easy for researchers to get experiments up and running. “We’re really shortening the learning loop so people can just start testing and programming today,” says Chad Rigetti, the company’s CEO and founder.

Though QCS will initially give researchers access only to the company’s 16-qubit chip, eventually its latest one will be accessible via the cloud too, the company says. The prospect of more powerful quantum processors excites researchers like Papenbrock. “With access to a 128-qubit chip, we could solve some fantastic problems,” he says.

Cloud moves

The new service will give even more researchers access to relatively advanced quantum computing and keep Rigetti in the front row of a rapidly expanding quantum cloud movement.

IBM already lets members of its business-focused QNetwork community access 20-qubit machines via the cloud, and provides free access to 5- and 16-qubit machines through an initiative called the IBM Quantum Experience. Dario Gil, the chief operating officer of IBM Research, says that some 97,000 users have run a total of 5.8 million experiments on the latter service since it launched in 2016.

At a recent conference, Diane Greene, the head of Google’s cloud business, said the company is letting a few customers have access to a cloud-based quantum service, and Asian tech firms like Japan’s Fujitsu and China’s Alibaba have also joined the quantum cloud club.