Microsoft’s Majorana 1 processor, a quantum computing device it claims contains eight  “topological” qubits. PHOTO: JOHN BRECHER/MICROSOFT

Dear Commons Community,

Physicists are casting doubt on claims by Microsoft of its “topological” qubit (photo above), a robust quantum analog of the 0-or-1 bit used in conventional computers.  As reported by Science.

On 18 March in an Anaheim, California, conference hall, Microsoft physicist Chetan Nayak faced a formidable challenge: convincing a standing-room audience of other scientists that his company had shaken the landscape of quantum computing. Nayak tried to make the case that his team had created the world’s first “topological” qubit, a robust quantum analog of the 0-or-1 bit used in conventional computers. Doing so would require not only conjuring the Majorana quasiparticle—a long-sought mode of electron behavior— but also controlling multiple Majoranas to encode quantum information.

Many audience members, however, weren’t sold. “I don’t think the data are convincing,” says Jelena Klinovaja, a physicist at the University of Basel who attended Nayak’s talk at the American Physical Society’s (APS’s) Global Physics Summit.

The claims received a similarly frosty reception at a talk the day before at the same meeting, when University of St. Andrews physicist Henry Legg—the author of two preprints challenging Microsoft’s work— declared that “any company claiming to have a topological qubit in 2025 is essentially selling a fairy tale.”

For his part, Nayak remains confident that his team has tamed the Majoranas. “We’ve only revealed a tiny fraction of what we’ve done,” he tells Science. “It’s going to look more and more convincing that this is going to be the basis of a technology.”

The furor began last month, when Microsoft proclaimed via a press release and a paper in Nature that it had achieved a breakthrough: a chip hosting eight Majorana-based topological qubits, which it says could yield utility-scale quantum computers in a matter of years. Quantum computing stocks soon rose, and Senator Ted Cruz (R–TX) touted the news on the Senate floor. In a social media post, Microsoft CEO Satya Nadella suggested the chip “could be quantum’s transistor moment.”

Microsoft’s paper, however, didn’t detail the chip or provide proof of Majoranas, focusing instead on a method for measuring certain quantum properties of a future device. Outraged by what they deemed to be hype, many physicists responded by posting fiery comments, barbed memes, and livestreamed takedowns online.

“I’ve never seen anything like this in my time in physics,” says Jason Alicea, a physicist at the California Institute of Technology. “The burden is on [Microsoft] to really show that what they have is the real deal.”

For decades, scientists have dreamed of better simulating nature and solving certain problems much faster by building computers that operate not on conventional bits— which can be set to either 0 or 1—but rather on qubits, which can be set to combinations of 0 and 1 simultaneously. But today’s quantum computers remain stifled by their qubits’ fragility to environmental noise.

Microsoft is trying to build qubit protection directly into its hardware by making qubits out of Majoranas, which are essentially delocalized electrons. Because the electrons don’t exist in any one location, their information can be protected “topologically” from any local disturbances under the right conditions.

Microsoft’s chip features ultrathin, superconducting indium-arsenide wires that force the electrons inside to form loose pairs. Each wire can also accommodate an extra unpaired electron, which effectively splits in half to occupy a Majorana at each end of the wire. A given wire’s two “parity” states—which would represent a 0 or 1 in a future computer—correspond to whether the wire contains an even or odd number of electrons. By measuring the chip in specific ways, Nayak’s team plans to shift and probe the wires’ parity states, thereby encoding and reading out quantum information.

To better define their search for the elusive Majoranas—whose discovery has been claimed and then debunked multiple times—Microsoft researchers devised a protocol in 2021 that tests whether a device can host the quasiparticles. The protocol consists of a computer simulation of their device they trained to identify Majorana-forming states. They then fed real measurements of the device into the same protocol to assess its state.

In 2023, Nayak’s team claimed to have built a device that passed the protocol; the new paper, published in Nature on 19 February, establishes a procedure for reading out the parity of the device’s nanowires. Microsoft claimed these results, along with new data hinted at in a press release, constituted “the world’s first quantum processor powered by topological qubits.”

Of the researchers who consider Microsoft’s claims overblown, Legg has been among the most forceful critics. A week after the company’s February announcement, he posted his first public challenge: a preprint that sharply criticized the reliability of Microsoft’s protocol for identifying Majoranas. “They have some explaining to do,” he says.

By digging into the protocol’s available code, Legg noticed that simply changing the measured ranges of a device’s different parameters, such as its magnetic field, appears to affect whether the device passes the protocol. Within each Microsoft experiment, Legg tells Science, the code used to evaluate real data also seems to be less restrictive than the code used for simulated data. And in another preprint posted on 11 March, Legg argues that raw data in Microsoft’s latest paper appear too disordered for the company’s device to have been harboring Majoranas.

In a 15 March LinkedIn post, Microsoft researcher Roman Lutchyn defended his team’s work, claiming the protocol’s sensitivity was expected and that the two versions of code yielded statistically similar outputs. During the Q&A session of Legg’s APS talk, Lutchyn issued his own challenge to Legg: “If you have a better idea, put forward a protocol, and then let’s all follow it.”

In his packed APS talk, Nayak unveiled a device that combines two nanowires into an H-shaped array that’s meant to demonstrate a functioning qubit. He then showed data describing the nanowires’ ability to exist in two distinct states that are complex combinations of 0 and 1, essential for the device to operate as a qubit.

Some in the audience were impressed by the engineering advances behind the doublenanowire device—but the new measurements were also met with skepticism. The data suggested a single nanowire would hold the 0 or 1 state for up to 10 milliseconds. However, the measurements Nayak presented for more complex states were far less clear. Statistical analysis suggested the complex states persisted for a few microseconds at a time. To some physicists in attendance, though, the data looked more like noise.

” would have loved for this to come out screaming at me that there’s only two [distinct] states,” says Cornell University physicist Eun-Ah Kim, who moderated the session. “But that’s not what I think I see.”

Despite many physicists’ qualms over Microsoft’s current evidence for a topological qubit, some, including University of Oxford physicist Steve Simon, remain hopeful: Recently, Simon bet Legg a Belgian beer that Nature won’t retract Microsoft’s paper in the next 2 years.

But for others such as Anton Akhmerov, a physicist at the Delft University of Technology, the overriding feeling is one of frustration—with both Microsoft’s sensational announcement and the backlash to it. “The problem is that both sides are making confident claims … and I don’t think either viewpoint is justified,” Akhmerov says. “It’d be nice if people would chill out a bit.”

This furor will not die down any time soon.  The ball is in Microsoft’s court.

Tony