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Hey! A step toward topological quantum computing - a way to compute that uses unusual properties of particles confined to wires or thin films.
Microsoft's press release is mainly about future plans, and the headline is pure hype, but their paper in Nature says what they've actually done.
They've created superconducting wires that contain 'Majorana zero modes', and figured out how to detect whether a wire has an even or odd number of these in it.
So what the hell are Majorana zero modes?
First, a Majorana particle is a spin-1/2 particle that is its own antiparticle. There are probably no fundamental particles like this in nature, though there's a chance neutrinos are Majorana particles. But we can create all sorts of 'quasiparticles' in cleverly designed materials. These are ways for atoms and electrons to wiggle that *act* like particles. And we can create Majorana quasiparticles in superconducting wires.
But what's a zero mode?
When a long thin spring vibrates up and down it can have 0, 1, 2, 3, ... wiggles in it. When it has 0, the whole spring is moving up and down in unison. That's a zero mode. In quantum mechanics, particles are waves, and wave that's a Majorana quasiparticle in a superconducting wire can be in a zero mode like this. So it's spread out through the whole length of the wire!
In short, this is pretty futuristic technology, and I really like the physics. Whether Microsoft can carry out their next steps and turn this into a useful computer, I have no idea. They claim they can do it in a few years, "not decades". 
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This article explains what's actually been done much more clearly than Microsoft's press release. But it could still be improved. For example:
"To understand Microsoft’s research, it’s essential to grasp the concept of Majorana zero modes, or MZMs."
That's true - but the article doesn't go on to explain that concept. 
If somebody wanted someone to *really* clearly explain what's going on, they would pay me. I'd be happy to do it!
But maybe they don't want this. Maybe the mystique of quantum computers is part of what sells the technology to investors.
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Finally, here is the paper in Nature, with dozens of authors. Here is the key passage that summarizes what's been done:
"We implement a single-shot interferometric measurement of fermion parity in indium arsenide–aluminium heterostructures with a gate-defined superconducting nanowire. The interferometer is formed by tunnel-coupling the proximitized nanowire to quantum dots. The nanowire causes a state-dependent shift of the quantum capacitance of these quantum dots of up to 1 femto-farad. Our quantum-capacitance measurements show flux h/2e-periodic bimodality with a signal-to-noise ratio of 1 in 3.6 microseconds at optimal flux values. From the time traces of the quantum-capacitance measurements, we extract a dwell time in the two associated states that is longer than 1 millisecond at in-plane magnetic fields of approximately 2 tesla."
I could expand this into text readable by mere mortals, but it's time for breakfast. Still: notice that these interesting states last for about a millisecond.
Note that the paper does not call these states Majorana zero modes. In the comments to my posts you'll see why! @marklfilteau points
out the referees say "the results in this manuscript do not represent evidence for the presence of Majorana zero modes in the reported devices". In short: something interesting is going on, but the paper doesn't prove that it's what Microsoft hopes it is.
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@johncarlosbaez "designed to scale to a million qubits on a single chip"
Is this before or after controlled nuclear fusion?
@dpiponi @johncarlosbaez Well Microsoft have a contract with Helion to deliver a Fusion reactor for energy to them in 2028/2029 - so it might be a close thing!
@dpiponi - it will be a fusion-powered device, run by a trained sasquatch.
@johncarlosbaez I'd say the key part of the article is here, which contradicts the press release.
Woah! Nice digging and also wtaf?!
@TonyVladusich @marklfilteau - nice digging! I'm not too surprised that their work did not *prove* what they are seeing is due to Majorana zero modes. It can be quite hard to rule out alternative explanations in condensed matter physics experiments. I'm not sure what the alternative explanations would be here.
@johncarlosbaez @TonyVladusich @marklfilteau The ridiculous press release aside, if one looks at the paper there is not really very good evidence for the parity measurement. It is not high quality and over a narrow range, and that is presumably the best data they had to put in the paper. But even if one accepts that they are seeing the right parity measurement then there are still other explanations than Majorana zero modes. I think it is now well understood that low energy states due to disorder are ubiquitous in these wires, and mimic most of the simple measurements you can do to detect the zero modes. There is the problem, measure enough wires and you will something Majorana-ish eventually, whether or not it is really there. There does not seem to be much discussion of these problems here on Mastodon that I can find, but on Bluesky one can find more, eg for a start https://bsky.app/profile/henrylegg.bsky.social .
“ If somebody wanted someone to *really* clearly explain what's going on, they would pay me. I'd be happy to do it!
But maybe they don't want this. Maybe the mystique of quantum computers is part of what sells the technology to investors.”
@johncarlosbaez fills me with dread. Quantum I get. Those bar stewards at Microarse I don't.