D-Wave, a quantum computing company based in Burnaby, Canada, has announced is “by far the largest and most powerful quantum computer in existence today”. The firm already has several clients using its new device, called Advantage, but others in the field have qualms about its claims, pointing out that both classical and quantum computers exist that exceed its capabilities.
Quantum computers use quantum bits, or qubits, to store information. While regular bits can only be in one of two states – a 0 or a 1 – qubits can be in a combination of those states, which allows them to hold more information at once. D-Wave’s new quantum device has 5000 qubits, more than any other quantum computer currently available, but the number of qubits isn’t a reliable measure of the power of a quantum device.
Find out more about quantum computing: at our upcoming online event
The qubits themselves are held in a chip similar to a regular circuit board. “On the chip, which is about the size of a thumbnail – it’s about eight millimetres on a side – there are about 110 metres of superconducting wiring that is mostly about one-quarter of a micron thick,” says Mark Johnson at D-Wave. “It’s an engineering feat just to have hundreds of wires going down to that chip and staying cold.” The chip needs to stay below about 15 millikelvin – near absolute zero – to function.
Advertisement
Yet experts point out the D-Wave device has limited use. “What they’ve built isn’t quite a quantum computer – it’s a piece of bespoke hardware that can solve a particular type of problem easily,” says Ciarán Gilligan-Lee at University College London. The D-Wave device can only solve optimisation problems, he says, such as finding the most efficient way to make a schedule or fold a protein.
Other quantum computers, such as Google’s 54-qubit Sycamore, are general-purpose devices like smartphones: you could use one as an alarm clock, but it has many other uses. The D-Wave device is more like a regular alarm clock, in that it has only one function that it does extremely well. “It might be the fanciest alarm clock that you’ve ever seen, but if you’re hoping that it’s a phone, you’ve got a shock coming,” says Gilligan-Lee.
“While D-Wave’s systems are particularly well-suited for optimisation, our computers are capable of solving an array of… problems,” says Alan Baratz, CEO of D-Wave. “Optimisation is one of them, which itself is widely applicable for a broad range of problem types and applications that have commercial value today.”
Despite being called Advantage, D-Wave’s device doesn’t achieve quantum advantage, a technical benchmark for quantum computers that would mark a major breakthrough. “Quantum advantage means demonstrating that, in a realistic setting with a practical problem, you can do something that no classical computer could do,” says Gilligan-Lee. “We have not done that yet.”
D-Wave hasn’t published any results showing that its device can outperform other computers, whether quantum or classical. Johnson says that D-Wave isn’t trying to achieve quantum advantage, but rather to provide customers with an advantage over the systems they were previously using.
“With many of these things, you could probably get a team of PhD computer scientists and they could probably come up with a classical algorithm that could surpass [the Advantage system] for a particular problem, but not every company is going to have access to an army of computer scientists,” he says.
While that may be an advantage for clients in business terms – D-Wave claims to have used its quantum computers as improvements on classical systems for clients ranging from Volkswagen to Accenture – it isn’t quantum advantage. In fact, other quantum computers built by the likes of IBM and Google can perform more complex calculations than Advantage and are advancing quickly. “The field has moved far beyond D-Wave’s way of doing things,” says Scott Aaronson at the University of Texas at Austin.
