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Henry Legg @PhysicsHenry
Joined December 2013
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Henry Legg@PhysicsHenry
28 Feb 2025
I had made Microsoft Quantum aware of issues before publication of their latest Nature paper (which uses the TGP to tune up their devices). Now I have made all issues public. In short: The topological gap protocol and all claims based on it are flawed. arxiv.org/abs/2502.19560

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I haven’t posted here for quite some time and I don't intend to post here ever again. This platform has changed significantly in the last few years. Recent events have only evinced the reasons I chose to leave. You can now find me primarily on Bluesky: bsky.app/profile/henrylegg.b…
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Microsoft's Majorana team are now cosplaying as "a small startup sitting inside a huge tech company" Just your typical shoestring outfit: 100 people and $1 billion burnt As if we needed any more evidence that this team is now fully detached from reality...
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The German press has been largely very good dealing with @MSFTQuantum’s nonsense. However, a little reminder: 😡Schottland ist nicht England!😡 🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿
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“The data was incredibly unconvincing. It is as if Microsoft Quantum was attempting a simultaneous Rorschach test on hundreds of people,” says physicist Henry Legg of the University of St. Andrews in Scotland sciencenews.org/article/micr…

Physicists are mostly unconvinced by Microsoft’s new topological quantum chip

Majorana qubits could be error resistant. But after a contentious talk at the Global Physics Summit, scientists aren’t convinced Microsoft has them.

sciencenews.org
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“If it’s possible to be less-than-underwhelmed, that would describe Legg, who gave a talk the day before Nayak’s” 🤷🏻‍♂️ What can I say? Microsoft’s results impressed me — with a negative sign.
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2025 Anaheim Global Physics Summit was overwhelmed by nonsensical noise presented by MSFT as evidence of a topological qubit after claiming to the world they had built one. There you go Sankar — I fixed your tweet for you.
Condensed Matter Theory Center@condensed_the
23 Mar 2025
2025 Anaheim Global Physics Summit was overwhelmed by nonsensical noise around MSFT quantum claims with no nuanced discussion on how almost-impossibly difficult it is to build a quantum computer in any platform, let alone the Majorana platform, fault-tolerance is ever-elusive
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Sunday stroll in the Scottish sunshine
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“The gap protocol is flawed,” said Henry Legg of the University of St Andrews. “The foundations to build a topological qubit aren’t there, and anyone claiming they have built one today is selling a dangerous fairy tale.” physics.aps.org/articles/v18…

Microsoft’s Claim of a Topological Qubit Faces Tough Questions

Microsoft’s announcement of achieving a milestone in a potentially transformative approach to quantum computing is met with skepticism by researchers attending the APS Global Summit.

physics.aps.org
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In their PRB Microsoft claimed no false positives in their simulations. Now they claim "it’s one in 700" — a meaningless number because of how they diluted the definition of topology for the original claim. Still, silly games can be fun: here’s another false positive.
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Also note just how much of phase space is supposedly "topological" in these simulations due to that diluted definition. By their original definition of topology (in Pikulin et al.) everything would be a false positive.
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Thoughts on the plane to Scotland about *that* talk: Main take home: As always, we are looking at a highly curated data set and even that is not at all convincing. Take this supposedly h/2e data: why does it start at 28.5 mT and end at 34 mT? What happens outside these ranges?
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more replies
We are told that 13 devices of this generation pass the topological gap protocol, but all the measurements of “Majorana 1” (appear) to be from a single device. What happened with those other devices? They were apparently functioning well enough for the TGP…
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On a personal note: It has been a very long few weeks since the Nature paper and my decision to write these comments. I am incredibly grateful for all the support of friends and colleagues. But I am now looking forward to a few days of tuning out and some normalcy.
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My summary slide yesterday: 1) We do not have a reliable way to detect Majoranas 2) The conductance data shows that there is no clear superconducting gap in these devices There is no reason to believe the noise presented today has anything to do with a topological qubit.
Henry Legg@PhysicsHenry
18 Mar 2025
Microsoft want you to believe this data shows the X measurement of a topological qubit. As an expert in this field here is my scientific take on what I see in this data: 💩💩💩💩💩
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The magnetic field ranges for the topological gap protocol of the two wires in Microsoft’s “tetron” are different. These wires are on the same chip! We know changing magnetic field range can change the TGP outcome. Explain please @MSFTQuantum
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Look what I found…
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Microsoft want you to believe this data shows the X measurement of a topological qubit. As an expert in this field here is my scientific take on what I see in this data: 💩💩💩💩💩
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Thank you to everyone that came to my talk today and all the support over the last few weeks. Today was an important day for protecting the scientific record #apsmarch
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