Confused by the quantum computing race? It’s just like the Oscars

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I watched Oppenheimer on the weekend, and aside from getting distracted by Einstein’s terrible wig, it got me thinking about the scientific arms race of our time: quantum computing.

Happily, the prize this time around is a computer rather than a bomb. As I wrote last week, the first nation to build a large-scale quantum computer will win enormous commercial, scientific and medical advantages, including the power to crack into the encrypted secrets of its enemies and rivals.

Fake!Credit: Alamy

That’s why the federal and Queensland governments have poured $1 billion into PsiQuantum to boost its efforts to build the world’s first commercially relevant quantum computer.

But there’s more than one horse in this race.

PsiQuantum, which harnesses photons of light for its computing, is freshly turbocharged by cash. However, a technological breakthrough on Tuesday evening is set to boost its rivals working on silicon-based quantum computing, while yet another approach – superconductors – is the current frontrunner backed by Google.

Each of these technologies is on the cusp of achieving error-corrected quantum computing with devices capable of overcoming mistakes (which are rife in the fragile world of qubits) and completing useful calculations. “It’s actually quite fascinating,” says theoretical quantum physicist Professor Stephen Bartlett from the University of Sydney. “The race is really neck and neck.”

US President Joe Biden looks at the IBM System One quantum computer. Unclear if he thought Tar was more impressive.Credit: AP

But it strikes me that this is less of a horse race with one winner and more like the Academy Awards, with multiple gongs up for grabs. Shall we meet the nominees?

A movie buff’s guide to quantum tech

Normal computer bits flick between two rigid states – zero and one – to perform their calculations.

In contrast, quantum bits, or qubits, capitalise on the strange laws of subatomic physics to hover in a state of “superposition” – both one, zero, and every possibility in between. Qubits are Everything Everywhere All at Once. That gives qubits enormous computing power – and there are many different ways to make one.

A qubit: Everything Everywhere All At Once.Credit: Roadshow

Cate Blanchett played a super conductor in Tár. But in physics, a superconductor is a material that, when cooled sufficiently, conducts electricity with no resistance. In a superconductor qubit, pairs of electrons whiz around a metal circuit cooled to almost absolute zero. Under these conditions, the circuit behaves like an atom that can be used for quantum calculations.

Tech giant IBM used superconductors to build the largest quantum computer yet, with 1121 qubits. This method is also backed by Google, so you could consider superconductors the quantum frontrunner. (And yet, Cate still lost the Oscar. Tragic.)

PsiQuantum, on the other hand, is pursuing photonic quantum computing, which uses particles of light, or photons, as qubits. (Photonic computing is like Muriel’s Wedding: it was made in Queensland, and it might take a few decades for people to appreciate its true genius).

Photons are promising because, like Muriel by the time the credits roll, they’re extremely independent. As Bartlett explains, they “don’t interact with anything”, can operate at room temperature and aren’t charged like electrons, so they’re not thrown off course by electromagnetic forces. The flip side of that, however, is that they’re difficult to control and measure. PsiQuantum’s set-up still needs to be very cold because the photons themselves are measured by superconductors.

Trapped ion quantum computers are another leading method. They’re created by grabbing atoms, flicking off an electron so they take a positive charge, suspending the charged atoms or “ions” within an electromagnetic field and then manipulating the ions with lasers. But the technology to trap and manipulate millions of ions at once does not yet exist.

There’s also silicon-based quantum computing, which has enormous interest in Australia. Silicon is made from sand. That’s right, we’re going to Dune.

The silicon sandworm: pure, hot and steaming ahead

Plenty of entrepreneurs and scientists have hitched their hopes to the proverbial sandworm of silicon quantum computing. Proponents say this method will be the fastest to scale up because it builds on the silicon chip manufacturing industry, which already powers our phones and laptops.

“Silicon’s a wonderful material, it’s the basis of the classical IT industry,” says Professor David Jamieson from the University of Melbourne. “But it suffers from one important drawback for a quantum device.”

A sandworm: less intimidating than quantum physics.Credit: Warner Bros

The problem, he says, is that 4.5 per cent of naturally occurring silicon contains silicon-29, which has an extra neutron. That rogue neutron acts like a magnet, throwing the electron qubits used in silicon quantum computing out of whack.

In research published on Tuesday, however, Jamieson and colleagues from the University of Manchester have found a way to purify that silicon. Using a device called an ion blaster, they scrubbed away all but 0.0002 per cent of the problem isotope.

That opens the door to transformative, error-corrected silicon quantum computing, says Jamieson.

Another barrier to quantum computing is that systems have to be kept at freezing temperatures, just above absolute zero, to work. That means quantum computers will have to be enormous to allow for powerful refrigeration systems and will suck up a lot of energy.

But Professor Andrew Dzurak recently reported in Nature that his “spin” electrons, trapped in adapted silicon transistors, can operate at temperatures 20 times warmer than previous systems. Dzurak says his company, Diraq, can make a quantum computer not much bigger than a laptop, kept in a cooling system the size of a kitchen fridge rather than the size of a building.

So, who’s most likely to win the quantum race? Like the Oscars, there are different categories where each kind of tech might excel. One might be first across the line, but our future may be powered by many kinds of qubits. Silicon quantum chips could end up in our phones. Photonic computing might revolutionise drug research, while superconductors could crack encryption.

As put by Dzurak: “Most governments around the world are spreading their bets by investing in a range of technologies.” Quantum researchers of all stripes are hoping our government does the same.

Examine, a free weekly newsletter covering science with a sceptical, evidence-based eye, is sent every Tuesday. You’re reading an excerpt – sign up to get the whole newsletter in your inbox.