Last month, John Preskill of Caltech’s Institute for Quantum Information and Matter quoted the late, colorful Nobel laureate Richard Feynman: “Nature isn’t classical dammit, and if you want to make a simulation of Nature you better make it quantum mechanical, and by golly it’s a wonderful problem because it doesn’t look so easy.”
Preskill says that a third of a century ago, Feynman was envisioning quantum computing. Now media observers are excitedly expecting quantum computers’ practical advent.
Voices like Preskill’s are calling for moderating the enthusiasm, but industry is stoking it. Google, IBM, Intel, Microsoft, and others have announced substantial progress, causing a wave of coverage. TechCrunch.com proclaimed that the “quantum computing apocalypse is imminent.” A Fox News headline trumpeted computing’s “mind-blowing future.” At Futurism it was “Quantum computing is going to change the world.”
At the New Statesman, Philip Ball examined commercial information technologists’ efforts to exploit the quantum realm. He described quantum computing as “the first major shift in how computing is done since electronic computing devices were invented.”
In November at Nature, Ball briefly summarized what makes a quantum computer truly quantum:
Quantum computers manipulate bits of information according to the quantum rules that govern the behaviour of matter on the smallest scales. In this quantum world, information can be coded as quantum bits (qubits), physically composed of objects that represent binary 1s and 0s as quantum states. By keeping the qubits in a coherent quantum superposition of states—so that in effect their settings are correlated, rather than being independent as in the bits (transistors) of classical computer circuitry—it becomes possible to carry out some computations much more efficiently, and thus faster, with far fewer (qu)bits, than on classical computers.
Expert summaries like that one serve as templates for the ones that journalists dutifully include. At the New York Times, three-time Pulitzer-winner Thomas Friedman used one from MIT Technology Review in his 17 January column on how China, the US National Security Agency, and others are “all racing . . . to build usable quantum systems.”
The competition metaphor of a race pervades the enthusiastic coverage. A recent Guardian editorial called quantum computing “the new space race.” The English-language South China Morning Post reported the view in China that a new national laboratory there means “a chance to win the race” to create a general-purpose quantum computer. In a US House of Representatives hearing last October, Science Committee chair Lamar Smith said that “although the US retains global leadership in the theoretical physics that underpins quantum computing and related technologies, we may be slipping behind others in developing the quantum applications.”
First step: Supremacy
But quantum computing actually involves two races, creating conditions for media enthusiasm to degrade into confusion.
The shorter race is for what Preskill in 2012 began calling quantum supremacy. That’s defined by MIT Technology Review as the “point at which a quantum machine should be able to perform computations too complex to model on any conventional machine.” The longer race is for the eventual advent of practical quantum computers.
Physicists’ intense current focus on possibly imminent quantum supremacy is easy for reporters to misinterpret. In the media’s enthusiastic race framing, it sounds like what reporters actually care about: the end of the longer race, with all that will presumably ensue.
Science magazine’s Adrian Cho reports that Google researchers have begun testing a 50-qubit chip, expecting to reach quantum supremacy. Cho’s article includes a “quantum computing to-do list” that outlines the devices’ greatest potential strengths, such as performing the kinds of quantum mechanical simulations that Feynman alluded to decades ago. But to emphasize the risk of inciting unrealistic expectations, Cho consulted physicist Irfan Siddiqi of Lawrence Berkeley National Laboratory. Not only is any such achievement not the end of the road, says Siddiqi, it’s “not even the beginning.”
So what exactly would constitute quantum supremacy? Consider the thumbnail summary beneath Ball’s Nature headline: “It’s far from obvious how to tell whether a quantum computer can outperform a classical one.”
Ball disputes those who say that quantum supremacy will arrive when there’s a sufficient qubit count. He asserts instead that the “true measure of the power of a quantum circuit is a combination of factors, which IBM researchers have called the quantum volume.” IBM defines that as a measure of “the useful amount of quantum computing done by a device in space and time.” He also quotes the view of IBM’s Edwin Pednault that “quantum supremacy should properly be viewed as a matter of degree, and not as an absolute threshold.” Pednault prefers the term quantum advantage.
Ball concludes that although the “idea of quantum supremacy sets a nice theoretical puzzle,” it “says little about what quantum computers might ultimately do for society.” He breaks down the supremacy concept further in a feature for Quanta, the first of a series on the future of quantum computing.
A transitional era
Media enthusiasts do have justification for excitement, but perhaps they should adopt the moderation inherent in Preskill’s suggested name for the interim period that will follow the achievement of quantum supremacy: the noisy intermediate-scale quantum, or NISQ, era.
In his January arXiv paper “Quantum computing in the NISQ era and beyond,” which is based on his keynote address at December’s Quantum Computing for Business conference in Silicon Valley, Preskill warns that even 100-qubit devices “will not change the world right away.” The main obstacle is noise, which precludes sustaining the coherent quantum superposition of states that Ball explained is so essential. “We’ll have imperfect control over those qubits; the noise will place serious limitations on what quantum devices can achieve in the near term,” Preskill writes.
Capturing Preskill’s caution doesn’t mean dampening the excitement over quantum computing, as Gizmodo writer Ryan F. Mandelbaum shows in a recent article urging attention to the NISQ concept. Indeed Preskill is still optimistic about the devices’ potential: “I do think that quantum computers will have transformative effects on society eventually, but these may still be decades away,” he writes in his paper. “We’re just not sure how long it’s going to take.”
Nevertheless the anticipation grows. BBC reports that last week the Australian of the Year, physicist Michelle Simmons, was honored in a ceremony led by Australia’s prime minister, Malcolm Turnbull. Her field: quantum computing.
Steven T. Corneliussen is Physics Today’s media analyst. He has published op-eds in the Washington Post and other newspapers, has written for NASA’s history program, and was a science writer at a particle-accelerator laboratory.
