Google's New Cirq Project Aims To Make Quantum Computers Actually Useful

A Hofstadter butterfly, a pattern describing how electrons behave in a magnetic field that’s been simulated by Google researchers. (Graphic: Wikimedia Commons user Mytomi, Wikimedia Commons)

Last year, we reported that a new era of quantum computing is upon us: The NISQ, or Noisy Intermediate Scale Quantum era, in which quantum computers are still small and error prone, but they actually do something valuable.

That second part is still somewhat aspirational, though, so companies such as Google are offering frameworks so the public can develop useful algorithms for quantum computers.

This week Google announced Cirq, its open-source framework for these NISQ computers. The framework doesn’t run on a real quantum computer yet (just a simulation of one) but will hopefully lead to quantum computers finding some use.

“Cirq is focused on near-term questions and helping researchers understand whether NISQ quantum computers are capable of solving computational problems of practical importance,” Alan Ho and Dave Bacon, product and software leads from the Google AI Quantum Team, wrote in a blog post.

Quantum computers are devices meant to perform calculations the way that traditional computers do, but with a different set of ground rules. Classical computer algorithms must ultimately be translated into zeroes and ones. Quantum algorithms instead rely on the mathematics of quantum computers, where the most basic unit is more like a point on a sphere during the calculation, but a zero or one for the final result.

These quantum bits, or qubits, communicate with one another through entanglement, the quantum mechanical idea where sets of multiple qubits are treated as mathematically indistinguishable units until the machine measures them.

These machines exist, but in their current state they are incredibly noisy, meaning they easily interact with nature and lose their quantum-ness, essentially becoming regular computers.

Some physicists think that existing quantum computers are becoming just complex enough to be useful, and could potentially solve some problems better than classical computers can. Researchers still must find out what problems those are — what problems could actually benefit from these noisy, intermediate-scale devices.

Google’s Cirq joins a slew of other frameworks that allow programmers to run quantum circuits. IBM has public-facing, 20- and 16-qubit devices, which programmers can play with and research using the IBM Q experience. Startup Rigetti has a 19-qubit device accessible through its Forest programming environment. Then there’s D-Wave, which also offers consumer products, but its computer works differently from the rest of the competition (more on that here).

Like Microsoft’s, Google’s framework is not built on real quantum hardware, but on a classical computer that simulates a quantum computer. Eventually, programmers will use Cirq to access Google’s upcoming 72-qubit Bristelcone processor.

Several startups have been testing Cirq prior to Google’s announcement. Quantum Benchmark, for example, offers what are essentially quantum diagnostic tools that can inform an end user about error rates in the quantum processor, and help to suppress those errors.

“Google has expertise that’s branded and recognisable, so it’s great for them to recognise the value that we’re bringing,” Quantum Benchmark CEO Joseph Emerson told Gizmodo.

One advantage of Google’s simulator is that users will eventually be able to run large-scale problems on it, said Matt Johnson, CEO of QCWare, a startup whose software allows clients to run quantum algorithms on multiple hardware platforms.

“It’s going to allow our customers to exploit what’s going to certainly be one of the leading hardware systems in terms of power.”

Still, we’re definitely in the early stages of this tech. Sydney Schreppler, postdoctoral fellow in physics and UC Berkeley, told Gizmodo that NISQ was a “hopeful” term.

“The hope is that industry-academia collaborations may result in some useful applications for the quantum processors that already exist in academic labs and at companies like Google, IBM and Rigetti.”

She said a new algorithm generated, or a link with actual hardware like Bristelcone, would be more exciting news, but that “cool new applications for existing hardware could be coming down the line”.

Development continues, with companies hoping to eventually find industry uses for these noisy quantum computers. But programmers and scientists have barely scratched the surface of quantum usefulness.

[Google AI Blog]

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