Henry Legg

Lecturer (~asst prof) investigating quantum physics @univofstandrews.

*** I do not post here anymore. Follow me on BlueSky instead ***

[Henry Legg @PhysicsHenry]

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.

https://t.co/fOX1hhOcCo

[Henry Legg @PhysicsHenry]

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: https://t.co/O9qhwSoVvk

[Henry Legg @PhysicsHenry]

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...

[Henry Legg @PhysicsHenry]

The German press has been largely very good dealing with @MSFTQuantum’s nonsense.

However, a little reminder:

😡Schottland ist nicht England!😡

🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁳󠁣󠁴󠁿

[Henry Legg @PhysicsHenry]

@jenseisert @Dr_Chetan_Nayak @MSFTResearch I detailed some further concerns about the data presented in the talk here: https://t.co/FBPWsK03I7

[Henry Legg @PhysicsHenry]

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?

[Henry Legg @PhysicsHenry]

“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

https://t.co/4beVc6pNe9

[Henry Legg @PhysicsHenry]

@jenseisert @Dr_Chetan_Nayak @MSFTResearch The talk involved cropped y-axes that made zero-bias peaks appear to go to zero when they did not.

These devices do not even exhibit features of superconductivity in the regime of interest, let alone topological superconductivity.

There is no reason to believe these claims.

[Henry Legg @PhysicsHenry]

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]

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

[Henry Legg @PhysicsHenry]

@charliwtquirks St Andrews is normally sunny (but windy!)

[Henry Legg @PhysicsHenry]

Sunday stroll in the Scottish sunshine

[Henry Legg @PhysicsHenry]

“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.”

https://t.co/MrITaM5Ey4

[Henry Legg @PhysicsHenry]

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.

[Henry Legg @PhysicsHenry]

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.

[Henry Legg @PhysicsHenry]

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.

[Henry Legg @PhysicsHenry]

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?

[Henry Legg @PhysicsHenry]

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…

[Henry Legg @PhysicsHenry]

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]

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: 💩💩💩💩💩

[Henry Legg @PhysicsHenry]

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