Quantum computing is red hot right now, not least after Google’s recent announcement that it had achieved quantum supremacy. An analysis by Nature shows the quantum hype is translating into a massive investment boost in the technology, but it might be a double-edged sword.

Quantum supremacy refers to the point at which a quantum computer can perform calculations beyond the most powerful classical computer imaginable. After all the hype about this milestone one might have expected a great fanfare when it was achieved, but instead the paper describing it was accidentally leaked by Google’s collaborators at NASA.

Nonetheless, it’s a significant marker. While the problem it solved was practically useless and chosen specifically to favor the quantum device, the man who coined the term, John Preskill, writes that it demonstrates the hardware works as we hoped it would.

Now starts the long journey to applying that quantum speedup to more useful problems, but despite the long timescales it will take for this to happen, money has been pouring into the field.

Google, IBM, and Intel have all been investing considerable sums into quantum computing for several years, but Nature found that in 2017 and 2018 quantum technology companies received at least $450 million in private funding—more than four times the $104 million disclosed over the previous two years.

Much of that money is coming from VC funds, raising the prospect of the same kind of boom as was seen in AI at the turn of the decade. But given that most experts think it’s still a long road to doing anything practical with quantum computers, there’s growing fear that all this excitement could lead to a “quantum winter.”

The term borrows from the AI industry, which prior to its recent boom has experienced two “AI winters.” Hype and unrealistic expectations led to a huge surge in interest followed by a dramatic retraction after disappointing progress saw investors pull out.

There’s growing fear in quantum computing circles that the breathless headlines around the race for quantum supremacy may have inflated expectations. Today’s devices are error-prone and measured in tens of qubits, but we will need to build machines of thousands if not millions of qubits to achieve an error-free, general-purpose quantum computer able to solve a broad selection of useful problems.

Nature notes a particularly worrying sign: a significant amount of investment so far has gone into quantum software companies, which are designing algorithms and programs for devices that don’t yet exist. Given that consensus still hasn’t developed on what the underlying materials of a quantum computer should be, that seems premature.

A more pernicious problem is the danger of a brain drain as companies flush with investor cash lure the best minds out of academia in a mirror of what has happened in AI. Given that there are still fundamental questions that need to be answered about quantum computing, in a field as small as it is that could severely hamper progress.

Ultimately, it’s a question of horizons. Few in the field doubt we will be able to build a powerful general-purpose quantum computer, but the question is whether investors are willing to wait the decades it could take to get there.

A solution to that quandary would be to find uses for the smaller, imperfect machines we have today. There’s a growing body of research in this direction, but even in the best-case scenario these devices will likely only be able to solve some niche problems in things like chemistry or optimization.

One saving grace is that quantum technology is not only about computers. Quantum communications and quantum cryptography have been making major advances in recent years and are likely to reach widespread commercial adoption considerably sooner, which could help maintain the field’s momentum.

There’s also considerable foresight about the potential for a quantum winter from within the industry. Michael Marthaler, co-founder of startup Heisenberg Quantum Simulations, told The Economist he’s already expecting one and is just hoping his firm is established enough by then to “hibernate.” Matthew Kinsella, managing director at Maverick Ventures, told Business Insider he’s preparing for a retraction despite having invested in a quantum technology company.

Given the nascent state of the field, there’s plenty of potential for a sudden breakthrough, for instance if silicon-based quantum computers make it possible to build large devices much sooner than expected, or Microsoft’s pursuit of far more stable topological qubits sidesteps the error-correction problem.

So don’t be surprised if the investors keep piling in.

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