The cat – a feline in a locked box that is both dead and alive until the box is opened – was a thought experiment devised by physicist Schrödinger to expose the counterintuitive weirdness of quantum theory. The theory posits that an entity can exist simultaneously in any number of states until the point at which it is observed, whereupon it will “collapse” into one state – either purring or deceased in the case of the trapped tabby, which is incarcerated with a poison that either has or has not been released through radioactive decay.

Geniuses have spotted that tapping into the quantum realm could release fantastic amounts of computing power. Where a classical bit must be either 0 or 1, a quantum bit, called a qubit, can be 0 or 1 – or, crucially, a mixture of both. Freed of this “either-or” constraint, even a modest quantum computer would vastly outpace the fastest supercomputer. Cracking the world’s toughest encryption software, which would take a supercomputer about 1m years, would be an hour’s work.

Google and Nasa have jointly forked out a reported $10m on a prototype quantum computer from D-Wave Systems, the only commercial company selling them.

D-Wave’s financial backers include Amazon founder Jeff Bezos, Goldman Sachs and the Canadian government. The company can claim “coolness” in another way: since atoms need to be cooled right down in order for quantum effects to appear, D-Wave’s laboratory near Vancouver houses possibly the coldest place on Earth, just 0.02C above absolute zero (the point at which atoms stop moving).

Where tech visionaries tread, national governments follow. The UK will be spending £270m over the next five years to establish centres of excellence. As the world demands ever more powerful computers, and as conventional chips reach their physical limits, early investors hope Schrödinger’s cat can be turned into a cash cow.

There is only one problem: there is a simmering debate over whether D-Wave’s quantum computers are actually quantum at all. Scott Aaronson, a quantum computing expert at Massachusetts Institute of Technology, says that while there is evidence for small-scale quantum effects, there is no definitive evidence that D-Wave has achieved a fully fledged quantum computer. Neither, Mr Aaronson says, is it faster than classical computers.

Now IBM researchers have waded in. Two weeks ago scientists from the IBM Thomas J Watson Research Center in New York, abetted by colleagues at the University of California, Berkeley, posted a paper entitled: “How ‘Quantum’ is the D-Wave Machine?” By taking on the same fiendish computing challenge posed to the D-Wave, and showing they could churn out pretty similar results with a classical algorithm, they claimed it was impossible to say definitively whether the machine was truly quantum.

Geordie Rose, D-Wave’s pugilistic founder who is also a former Canadian wrestling champion, defended his machine and accused his detractors of cherry-picking data. On his Hack the Multiverse blog, he wrote: “When I saw how trivially wrong [the paper] was, it was like opening a Christmas present and getting socks.” Ouch.

For all the delicious backbiting and ego-baiting and megamoney gambles, quantum computing really does look like the natural next step in computational problem-solving, even if it can only crack a limited class of problems. In these early days of the revolution, we may have to take it on faith that the quantum computers around today are the real deal.

Still, there is a pleasing irony to the uncertainty. Central to quantum theory is Heisenberg’s uncertainty principle, which states that we can never measure every property of a particle to the utmost precision. The universe places fundamental limits on our ability to know: just as the fate of Schrödinger’s famous cat remains a mystery to anyone outside the box, so, perhaps, does the truth about today’s quantum computers.