Quantized Majorana conductance

Get your science fix here: research, quackery, activism and all the rest
Post Reply
User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Quantized Majorana conductance

Post by shpalman » Tue Mar 09, 2021 1:40 pm

... is not a thing: https://www.nature.com/articles/s41586-021-03373-x

Or at least, that paper which claimed to have demonstrated it turns out to have been very shonky indeed.

the Register;

full scientific takedown.

report from independent experts.

"there is no future if we don't learn from this"
molto tricky

User avatar
jimbob
After Pie
Posts: 2331
Joined: Mon Nov 11, 2019 4:04 pm
Location: High Peak/Manchester

Re: Quantized Majorana conductance

Post by jimbob » Tue Mar 09, 2021 2:19 pm

shpalman wrote:
Tue Mar 09, 2021 1:40 pm
... is not a thing: https://www.nature.com/articles/s41586-021-03373-x

Or at least, that paper which claimed to have demonstrated it turns out to have been very shonky indeed.

the Register;

full scientific takedown.

report from independent experts.

"there is no future if we don't learn from this"
Shades of the Bell Labs retractions from quite a few years ago
Have you considered stupidity as an explanation

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Tue Mar 09, 2021 2:46 pm

Also at wired.

Das Sarma, who is one of the coauthors, was "convinced that these strange particles exist in these nanowires" but was not fooled at all into thinking that Majorana modes have been seen in 2018.

https://twitter.com/condensed_the/statu ... 2931175427
CMTC, director: Das Sarma wrote:What do people want to hear about during the CMTC APS talk on March 15? CMTC has total command over all aspects of Majorana, but the allotted time is 30 minutes. Experiments will be discussed, emphasizing how to find Majorana. They exist, but have not yet been seen in the labs
https://twitter.com/VincentMourik/statu ... 1386303493
one of the authors of the pdf presentation takedown wrote:Could you please explain the theory supporting the now retracted nature 2018 paper on which you are a senior PI? Since the experimental plateau is proven to be non-existent why didn't your theory intercept that? How is it wrong? Explanation much appreciated.
molto tricky

User avatar
Brightonian
Catbabel
Posts: 626
Joined: Mon Nov 11, 2019 3:16 pm
Location: Usually UK, often France and Ireland

Re: Quantized Majorana conductance

Post by Brightonian » Tue Mar 09, 2021 3:06 pm

At the risk of drifting from this Nerd Lab topic, I'd not heard of 'Majorana' before. 'Conductance' sounds like a word, and of course there's it's all 'quantized' so I get it, it's about a high bus worker with a machine made by Sir Clive Sinclair. Mods, do slap me down if you want, it won't hurt as I'm on my third glass of wine now.

The Wikipedia page for Majorana says Fermi suggested he was on a par with Galileo and Newton, but I'd never heard of him. Also suggests he "escaped" to South America, but what he was escaping from, we don't know (himself, it sounds like, as he'd become of a bit of a hermit).

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Tue Mar 09, 2021 3:23 pm

He suggested you could have a particle which was its own antiparticle, which all known particles are not.*

But you might apparently get something happening in a superconductor which behaves like that, except that you don't.
molto tricky

User avatar
dyqik
Stummy Beige
Posts: 3546
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: Quantized Majorana conductance

Post by dyqik » Tue Mar 09, 2021 6:02 pm

shpalman wrote:
Tue Mar 09, 2021 3:23 pm
He suggested you could have a particle which was its own antiparticle, which all known particles are not.*

But you might apparently get something happening in a superconductor which behaves like that, except that you don't.
*except photons. And Z bosons. And the Higgs. And the neutral pion. I think you mean "fermion which is its own antiparticle".

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Tue Mar 09, 2021 6:07 pm

dyqik wrote:
Tue Mar 09, 2021 6:02 pm
shpalman wrote:
Tue Mar 09, 2021 3:23 pm
He suggested you could have a particle which was its own antiparticle, which all known particles are not.*

But you might apparently get something happening in a superconductor which behaves like that, except that you don't.
*except photons. And Z bosons. And the Higgs. And the neutral pion. I think you mean "fermion which is its own antiparticle".
Feel free to explain to Brightonian what a fermion is.
molto tricky

User avatar
dyqik
Stummy Beige
Posts: 3546
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: Quantized Majorana conductance

Post by dyqik » Tue Mar 09, 2021 6:10 pm

shpalman wrote:
Tue Mar 09, 2021 6:07 pm
dyqik wrote:
Tue Mar 09, 2021 6:02 pm
shpalman wrote:
Tue Mar 09, 2021 3:23 pm
He suggested you could have a particle which was its own antiparticle, which all known particles are not.*

But you might apparently get something happening in a superconductor which behaves like that, except that you don't.
*except photons. And Z bosons. And the Higgs. And the neutral pion. I think you mean "fermion which is its own antiparticle".
Feel free to explain to Brightonian what a fermion is.
It's a particular type of particle that can't be its own antiparticle in standard particle physics.

:P

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Wed Mar 10, 2021 10:44 pm

https://www.bbc.com/news/technology-56328980

Not that it really adds anything.
molto tricky

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Thu Mar 11, 2021 8:52 am

dyqik wrote:
Tue Mar 09, 2021 6:02 pm
shpalman wrote:
Tue Mar 09, 2021 3:23 pm
He suggested you could have a particle which was its own antiparticle, which all known particles are not.*

But you might apparently get something happening in a superconductor which behaves like that, except that you don't.
*except photons. And Z bosons. And the Higgs. And the neutral pion. I think you mean "fermion which is its own antiparticle".
Photons, Z bosons, and the Higgs aren't particles, they're waves. And the neutral pion isn't a particle, it's two particles.

There was a review article, New directions in the pursuit of Majorana fermions in solid state systems (well, they were new 9-10 years ago) but the abstract starts with "The 1937 theoretical discovery of Majorana fermions..."

A theoretical "discovery" isn't a discovery of anything.

Majorana's last paper was something about The value of statistical laws in physics and social sciences which I think is finally available here.
The deterministic conception of nature implies in itself a real cause of weakness in the irremediable contradiction that it faces with the most certain data of our consciousness. G. SOREL attempted to compose this disagreement with the distinction between artificial nature and natural nature (this last acausal), but in this way he denied the unity of science. On the other hand, the formal analogy between the statistical laws of physics and the ones of social sciences credited the opinion that human facts also undergo a rigid determinism. It is therefore important that quantum mechanics principles have brought to recognize the statistical character of basic laws of elementary processes, in addition to a certain absence of objectiveness in the description of phenomena. This conclusion has made essential the analogy between physics and social sciences, between which it turned out an identity of value and method.
Hm.
molto tricky

User avatar
Martin Y
After Pie
Posts: 1876
Joined: Mon Nov 11, 2019 1:08 pm

Re: Quantized Majorana conductance

Post by Martin Y » Thu Mar 11, 2021 9:57 am

shpalman wrote:
Wed Mar 10, 2021 10:44 pm
https://www.bbc.com/news/technology-56328980

Not that it really adds anything.
Well, it has the handy guide "Quantum computing explained in 20 seconds" which only takes 20 seconds, has clever people saying some things about quantum computing and doesn't explain quantum computing at all.

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Thu Mar 11, 2021 10:18 am

Martin Y wrote:
Thu Mar 11, 2021 9:57 am
shpalman wrote:
Wed Mar 10, 2021 10:44 pm
https://www.bbc.com/news/technology-56328980

Not that it really adds anything.
Well, it has the handy guide "Quantum computing explained in 20 seconds" which only takes 20 seconds, has clever people saying some things about quantum computing and doesn't explain quantum computing at all.
I've managed to get myself signed up for a course which will be two hours a week from now until June, explaining how to do quantum computing (with qiskit) via IBM's platform.

The BBC link also describes the Majorana as a "subatomic particle" which it wouldn't be in this context. It would be the behaviour of lots of electrons* making it look as if there was a Majorana.

(* - Even in a metal, for example, it's convenient to think of it being full of electrons running around conducting electricity, but it's wrong, because the electrons fill up the metal like water filling up a glass of water and their movement through the metal needs to vibe with the arrangement of atoms in the metal like walking on the pavement without stepping on the cracks; anyone with some experience in solid state physics and quantum mechanics generally will look at the necessary equations and immediately think f.ck that sh.t let's just pretend they're electrons running around and if necessary we'll just tweak their properties to fit what we measure. "Quasiparticles" in solid state physics - semiconductors and superconductors especially - are basically physicists saying f.ck that sh.t we're going to pretend these weird arrangements and interactions of electrons in here are just behaving as if it were some new particle, and then we can just play with those particles as if they're a thing. Majoranas in this case would be a particular kind of quasiparticle, except they aren't because nobody has seen any evidence for them yet.)
molto tricky

User avatar
jimbob
After Pie
Posts: 2331
Joined: Mon Nov 11, 2019 4:04 pm
Location: High Peak/Manchester

Re: Quantized Majorana conductance

Post by jimbob » Thu Mar 11, 2021 10:30 am

shpalman wrote:
Thu Mar 11, 2021 10:18 am
Martin Y wrote:
Thu Mar 11, 2021 9:57 am
shpalman wrote:
Wed Mar 10, 2021 10:44 pm
https://www.bbc.com/news/technology-56328980

Not that it really adds anything.
Well, it has the handy guide "Quantum computing explained in 20 seconds" which only takes 20 seconds, has clever people saying some things about quantum computing and doesn't explain quantum computing at all.
I've managed to get myself signed up for a course which will be two hours a week from now until June, explaining how to do quantum computing (with qiskit) via IBM's platform.

The BBC link also describes the Majorana as a "subatomic particle" which it wouldn't be in this context. It would be the behaviour of lots of electrons* making it look as if there was a Majorana.

(* - Even in a metal, for example, it's convenient to think of it being full of electrons running around conducting electricity, but it's wrong, because the electrons fill up the metal like water filling up a glass of water and their movement through the metal needs to vibe with the arrangement of atoms in the metal like walking on the pavement without stepping on the cracks; anyone with some experience in solid state physics and quantum mechanics generally will look at the necessary equations and immediately think f.ck that sh.t let's just pretend they're electrons running around and if necessary we'll just tweak their properties to fit what we measure. "Quasiparticles" in solid state physics - semiconductors and superconductors especially - are basically physicists saying f.ck that sh.t we're going to pretend these weird arrangements and interactions of electrons in here are just behaving as if it were some new particle, and then we can just play with those particles as if they're a thing. Majoranas in this case would be a particular kind of quasiparticle, except they aren't because nobody has seen any evidence for them yet.)
A colleague and our former boss spent about 15 years that I know of arguing whether the concept of holes was useful. In fact they probably still are.
Have you considered stupidity as an explanation

User avatar
shpalman
Stummy Beige
Posts: 3940
Joined: Mon Nov 11, 2019 12:53 pm
Location: One step beyond

Re: Quantized Majorana conductance

Post by shpalman » Thu Mar 11, 2021 10:34 am

I wonder if holes should be considered as having the electron's (negative) charge and a negative mass, rather than a positive charge (equal but opposite to the electron) and a positive mass.

(Both electrons and holes in a semiconductor tend to have a mass which is somewhat less than the mass of an electron in free space, in terms of how much electric force is necessary to get them to move or rather the relationship between their momentum* and energy).
molto tricky

User avatar
dyqik
Stummy Beige
Posts: 3546
Joined: Wed Sep 25, 2019 4:19 pm
Location: Masshole
Contact:

Re: Quantized Majorana conductance

Post by dyqik » Thu Mar 11, 2021 11:16 am

shpalman wrote:
Thu Mar 11, 2021 8:52 am
dyqik wrote:
Tue Mar 09, 2021 6:02 pm
shpalman wrote:
Tue Mar 09, 2021 3:23 pm
He suggested you could have a particle which was its own antiparticle, which all known particles are not.*

But you might apparently get something happening in a superconductor which behaves like that, except that you don't.
*except photons. And Z bosons. And the Higgs. And the neutral pion. I think you mean "fermion which is its own antiparticle".
Photons, Z bosons, and the Higgs aren't particles, they're waves. And the neutral pion isn't a particle, it's two particles.
Er, no.

They are all particles, to the same extent that anything else is a particle.

monkey
Snowbonk
Posts: 470
Joined: Wed Nov 13, 2019 5:10 pm

Re: Quantized Majorana conductance

Post by monkey » Thu Mar 11, 2021 3:58 pm

dyqik wrote:
Thu Mar 11, 2021 11:16 am
shpalman wrote:
Thu Mar 11, 2021 8:52 am
dyqik wrote:
Tue Mar 09, 2021 6:02 pm


*except photons. And Z bosons. And the Higgs. And the neutral pion. I think you mean "fermion which is its own antiparticle".
Photons, Z bosons, and the Higgs aren't particles, they're waves. And the neutral pion isn't a particle, it's two particles.
Er, no.

They are all particles, to the same extent that anything else is a particle.
But they are also all waves, to the the same extent that anything else is a wave :P

User avatar
jimbob
After Pie
Posts: 2331
Joined: Mon Nov 11, 2019 4:04 pm
Location: High Peak/Manchester

Re: Quantized Majorana conductance

Post by jimbob » Thu Mar 11, 2021 4:42 pm

monkey wrote:
Thu Mar 11, 2021 3:58 pm
dyqik wrote:
Thu Mar 11, 2021 11:16 am
shpalman wrote:
Thu Mar 11, 2021 8:52 am

Photons, Z bosons, and the Higgs aren't particles, they're waves. And the neutral pion isn't a particle, it's two particles.
Er, no.

They are all particles, to the same extent that anything else is a particle.
But they are also all waves, to the the same extent that anything else is a wave :P
Otherwise diffraction really wouldn't work on them.
Have you considered stupidity as an explanation

Post Reply