Putting quantum advancement in perspective
Some quantum-computing experts doubt that the breakthrough is as big as Microsoft and Quantinuum are painting it to be. “Microsoft itself says it needs to improve the fidelity by at least three orders of magnitude,” says Omdia’s Lucero.
And the experiment only showed Clifford gates, he says. Clifford gates only support some types of computations. This means that the logical qubits Microsoft demonstrated aren’t enough for a full universal computer, he says. “Non-Clifford gate functionality will have to be added at some point.”
And four logical qubits is a ways away from the 100 needed for scientific value, he adds.
On a positive note, this means that current encryption methods are still safe. “It appears that about 2,000 logical qubits will be needed to run Shor’s algorithm sufficiently to break AES 256-bit encryption,” Lucero says.
Microsoft may have also cherry-picked results to get the attention-grabbing headline, says David Shaw, chief analyst at Global Quantum Intelligence. “They allow themselves to discard runs that didn’t work,” he says. “So you kind of have to squint to see that there was any error improvement. It was impressive, but you had to squint.”
In other words, we don’t yet have a Sputnik moment for quantum computing, he says. “We’ve seen a rocket engine ignite. A static burn test, rather than getting your stuff into orbit.”
It’s not immediately clear how Microsoft’s approach could be used in a scalable way to suppress errors, or how it would apply to universal quantum gates.
“Yes, it is a good milestone,” Shaw says. “The debate that’s there in the field is how soon can we build large-scale fault-tolerant systems. This doesn’t really change the debate. A four-logical-qubit machine would have scientific interest, and maybe niche applications, but they’re not likely to be general-purpose, widely usable applications.”
Other companies have built quantum computers with more qubits. But quantum computing today is so nascent that there are multiple and radically different approaches to building the physical qubits.
Microsoft’s approach is heavily dependent on Quantinuum’s quantum-computing hardware, says Baptiste Royer, professor at the University of Sherbrooke, so it’s not immediately likely that other companies will jump on this same technology. “But they might be inspired by the theory behind this,” he says.
According to Royer, the latest announcement is the result of a series of small improvements – in addition to the error-correction codes, there were also improvements in the hardware, in calibration, in fabrication, in precision, as well as new measurement protocols.
As a result, there are no significant, immediate benefits for enterprises looking for practical quantum computing, especially with the smaller number of logical qubits.
“In terms of researchers looking at error correction, this gives them a playground to test things,” Royer says. “For researchers, this is exciting. In terms of the general public, I don’t see any immediate practical impacts – but it will bring quantum computing closer and reduce the time it will take to get to the practical things.”
