Microsoft Defends Topological Qubit Claims at APS Meeting Amid Skepticism

Insider Brief

• Microsoft defended its claim of creating topological qubits at the American Physical Society conference earlier this week, but skepticism remains over whether it has achieved a significant quantum computing milestone.
• Physicists raised concerns about Microsoft’s verification methods, particularly the reliability of the topological gap protocol (TGP) in detecting Majorana quasiparticles.
• Microsoft maintains confidence in its results and plans to release additional details in a forthcoming paper on arXiv.

Microsoft defended its topological qubit claims at a major physics conference this week, but skepticism lingers over whether the company has achieved a long-sought quantum computing milestone.

Chetan Nayak, a theoretical physicist leading Microsoft’s quantum computing effort, presented the company’s findings at the American Physical Society (APS) meeting, laying out the technical underpinnings of its claim to have created the first topological qubits, Nature is reporting. Microsoft first announced the achievement on Feb. 19, but its assertion remains unproven in the eyes of much of the scientific community.

Physicists in attendance expressed doubts. “It’s a hard problem,” said Ali Yazdani, an experimental physicist at Princeton University. To researchers trying to make topological qubits, he said, “good luck.” Daniel Loss, a theorist at the University of Basel in Switzerland, called Microsoft’s talk impressive but said, “People have gone overboard, and the community is not happy. They overdid it.”

However, some experts are suggesting that the debate shouldn’t be viewed negatively — it’s a normal part of the scientific process.

“Somebody takes a look at what someone else was doing, they poke holes,” said Jason Alicea, a theorist at the California Institute of Technology. “This is what scientists should be doing.”

Nayak, acknowledging the skepticism, said, “I never felt like there would be one moment when everyone is fully convinced.” He insisted that Microsoft’s team was confident in its results and that other researchers were intrigued by the approach.

Scrutiny Over Microsoft’s Claims

The debate over Microsoft’s topological qubits escalated two weeks after the company’s initial announcement when physicist Henry Legg of the University of St Andrews published a report on the preprint server arXiv casting doubt on Microsoft’s verification methods. Legg, who also presented his findings at APS, argued that Microsoft’s key test for detecting the quasiparticles necessary for topological qubits was unreliable, according to Nature.

Microsoft’s devices rely on Majorana quasiparticles, exotic entities that emerge from the collective behavior of electrons in certain materials. The company’s schematic, presented by Nayak, showed microscopic, H-shaped aluminum wires atop a layer of indium arsenide, a superconducting material, according to Nature. The goal is for Majoranas to form at the four tips of the H-shaped wire, where they would help protect quantum information from external noise.

But the evidence remains contentious. Nayak presented measurements known as ‘X’ and ‘Z’ probes, taken along the H-shaped wire, as evidence that the system functions as a topological qubit. However, when showing the data for the X measurement, he admitted that the key signal was difficult to see due to electrical noise.

Eun-Ah Kim, a theorist at Cornell University, told Nature she was unconvinced by the X measurement. Kim recommended better clarity in upcoming work.

“I’d like to see the bimodality be easily visible in future experiments,” she told the journal.

Challenges with Microsoft’s Verification Test

A central point of contention is Microsoft’s reliance on the topological gap protocol (TGP), a test — which works by measuring energy differences in the system — that the company developed to confirm the presence of Majoranas. Legg’s analysis suggested the test could produce false positives, undermining its reliability. In his APS presentation, Legg detailed how Microsoft’s implementation of the protocol led to inconsistencies, which could mean the system does not behave as a topological qubit.

Roman Lutchyn, a Microsoft physicist in the audience, pushed back, saying Legg had identified only “one instance out of 700” where the test produced misleading results, according to Nature.

Lutchyn, responding on LinkedIn, further argued that the phenomenon was “expected and does not invalidate the use of the protocol with correctly chosen parameters.”

In prior statements, Nayak dismissed Legg’s critique as a “false straw man” and a “non-issue.” But several physicists told Nature that the concerns were valid.

A related issue is the dependence of Microsoft’s test on the chosen range of experimental parameters. According to Legg’s report, a device that passes the test over a broad magnetic field range — such as 1.4 to 3 Tesla — fails when the range narrows to 1.8 to 3 Tesla.

“This seems like a bug in the protocol that needs to be worked out,” said Alicea, according to Nature.

IEEE Spectrum reports that Microsoft’s quantum team recently invited several researchers in the topological quantum computing field to a meeting at their headquarters at Station Q to review preliminary results demonstrating another such measurement.

“There’s still quite a bit of work to do on that side,” Michael Eggleston, data and devices leader at Nokia, who was present at the Station Q meeting, told IEEE Spectrum. “There’s a lot of noise in that system. But I think they’re on a good path.”

Microsoft said it would provide additional details in a forthcoming paper to be posted on arXiv.