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Quantized Majorana conductance
- shpalman
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Re: Quantized Majorana conductance
Spin qubits in germanium work though.
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Quantized Majorana conductance
NISQ Is Dead, a Dying Dead End, With No Prospects for a Brighter Future or Practical Quantum Computing
You just need "near-perfect qubits" instead. Well ok then why didn't you say.
You just need "near-perfect qubits" instead. Well ok then why didn't you say.
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Quantized Majorana conductance
In addition to not existing as quasiparticles in solid state systems, Majorana fermions also do not exist as fundamental particles.
"The fact that we didn't detect anything demonstrates the feasibility of spending a whole bunch more money to not detect anything on a much bigger scale" said a particle physicist, again.
"The fact that we didn't detect anything demonstrates the feasibility of spending a whole bunch more money to not detect anything on a much bigger scale" said a particle physicist, again.
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Quantized Majorana conductance
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Quantized Majorana conductance
Only just got around to looking at this. At some point it says, "While neutrinos have already been found to have a mass..."shpalman wrote: ↑Fri Mar 03, 2023 11:58 amIn addition to not existing as quasiparticles in solid state systems, Majorana fermions also do not exist as fundamental particles.
"The fact that we didn't detect anything demonstrates the feasibility of spending a whole bunch more money to not detect anything on a much bigger scale" said a particle physicist, again.
I think to say that a neutrino has a mass, you have to demonstrate a non-zero lower bound for it. That does not seem to have been achieved.
It seems the justification for the above statement is neutrino oscillations. By some well-established theory, that can only happen if they have a mass. But whilst our well-established are excellent in their core zones, they are rather less reliable outside their known reliable areas of application, to the extent of appearing to be completely inconsistent with major facts. So I'm not convinced by this demonstration by a theory that has not been proven to be correct in relation to neutrinos.
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Re: Quantized Majorana conductance
The neutrino has to have mass otherwise it would travel at the speed of light, and at the speed of light time would not evolve for it in our frame. So to be able to oscillate, time must be passing in its frame. Special relativity is simple and fundamental enough that for it to be wrong would be a major upset.IvanV wrote: ↑Thu Jun 22, 2023 10:27 amOnly just got around to looking at this. At some point it says, "While neutrinos have already been found to have a mass..."shpalman wrote: ↑Fri Mar 03, 2023 11:58 amIn addition to not existing as quasiparticles in solid state systems, Majorana fermions also do not exist as fundamental particles.
"The fact that we didn't detect anything demonstrates the feasibility of spending a whole bunch more money to not detect anything on a much bigger scale" said a particle physicist, again.
I think to say that a neutrino has a mass, you have to demonstrate a non-zero lower bound for it. That does not seem to have been achieved.
It seems the justification for the above statement is neutrino oscillations. By some well-established theory, that can only happen if they have a mass. But whilst our well-established are excellent in their core zones, they are rather less reliable outside their known reliable areas of application, to the extent of appearing to be completely inconsistent with major facts. So I'm not convinced by this demonstration by a theory that has not been proven to be correct in relation to neutrinos.
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Quantized Majorana conductance
Yet several measurements of neutrino speed have been unable to distinguish it from the speed of light.shpalman wrote: ↑Thu Jun 22, 2023 10:33 amThe neutrino has to have mass otherwise it would travel at the speed of light, and at the speed of light time would not evolve for it in our frame. So to be able to oscillate, time must be passing in its frame. Special relativity is simple and fundamental enough that for it to be wrong would be a major upset.
To me, the neutrino mass is in the same box as supersymmetric particles.
Re: Quantized Majorana conductance
Then you're an idiot who doesn't know what you're talking about.IvanV wrote: ↑Fri Jun 23, 2023 2:07 pmYet several measurements of neutrino speed have been unable to distinguish it from the speed of light.shpalman wrote: ↑Thu Jun 22, 2023 10:33 amThe neutrino has to have mass otherwise it would travel at the speed of light, and at the speed of light time would not evolve for it in our frame. So to be able to oscillate, time must be passing in its frame. Special relativity is simple and fundamental enough that for it to be wrong would be a major upset.
To me, the neutrino mass is in the same box as supersymmetric particles.
Neutrinos have mass. We know that because they oscillate, which they could not do if they traveled at the speed of light.
If they don't have mass, then special relativity, quantum mechanics and general relativity are wrong.
I'm building a $660 million experiment to determine that mass.
Re: Quantized Majorana conductance
And I hope that you show they do have a mass, because we learn something from positive findings, whereas negative findings leave us still unsure.dyqik wrote: ↑Fri Jun 23, 2023 2:17 pmThen you're an idiot who doesn't know what you're talking about.
Neutrinos have mass. We know that because they oscillate, which they could not do if they traveled at the speed of light.
If they don't have mass, then special relativity, quantum mechanics and general relativity are wrong.
I'm building a $660 million experiment to determine that mass.
A few years ago, some very clever people who seemingly utterly believed in super-symmetry used similar language against the doubters, and stated seemingly for certain that the LHC would vindicate them. Clearly super-symmetry isn't disproved, but there is a much narrower window of possibility for it to be true, and such people are less combative about it these days. Likewise, the failure of your experiment wouldn't disprove neutrino mass, we still wouldn't know either way, but it would be looking less likely. And it might be more difficult to get funding for an even more expensive experiment that might put an even lower upper limit on it.
I think we already know that some of these famous theories have to be wrong, but in the positive way that Newton's Laws are wrong - they have a range of application, and you need to know something else at the edges where they start to contradict each other, or where we have physical knowledge that is hard to make sense of. That kind of "wrong theory" is much more useful and insightful than those that are not even wrong.
Re: Quantized Majorana conductance
Again, you are clearly showing that you don't know what you are talking about.
Supersymmetry has never had a direct evidence base. Meanwhile, special relativity and electroweak theory are proven by huge amounts of evidence.
Supersymmetry has never had a direct evidence base. Meanwhile, special relativity and electroweak theory are proven by huge amounts of evidence.
Re: Quantized Majorana conductance
An interesting suggestion that there will be a joint announcement next week from
- a team attempting to detect GW waves through the measurement of deviations to the timing Pulsar signals
- a team using the Ice Cube Neutrino Observatory in Antarctica.
This may allow us to determine the speed at which neutrinos travel relative to the speed of light.
So far, we know (in part following the neutrino burst detected a few hours before* the gamma ray burst for the SN1987A supernova) that if there's a difference between the speed of neutrinos and light, it's only a few parts per billion, It'll be interesting to see if the announcement helps to narrow it down.
* neutrinos arrive first as they are created as the core collapses, and escape almost immediately, whereas the gamma rays emitted have to battle through the outer layers of the collapsing star before they are emitted.
- a team attempting to detect GW waves through the measurement of deviations to the timing Pulsar signals
- a team using the Ice Cube Neutrino Observatory in Antarctica.
This may allow us to determine the speed at which neutrinos travel relative to the speed of light.
So far, we know (in part following the neutrino burst detected a few hours before* the gamma ray burst for the SN1987A supernova) that if there's a difference between the speed of neutrinos and light, it's only a few parts per billion, It'll be interesting to see if the announcement helps to narrow it down.
* neutrinos arrive first as they are created as the core collapses, and escape almost immediately, whereas the gamma rays emitted have to battle through the outer layers of the collapsing star before they are emitted.
My avatar was a scientific result that was later found to be 'mistaken' - I rarely claim to be 100% correct
ETA 5/8/20: I've been advised that the result was correct, it was the initial interpretation that needed to be withdrawn
Meta? I'd say so!
ETA 5/8/20: I've been advised that the result was correct, it was the initial interpretation that needed to be withdrawn
Meta? I'd say so!
Re: Quantized Majorana conductance
I did a bit more reading and see I was ignorant, my apologies.
I thought this was going to be an unbounded game where we could just keep pushing it down a few more orders of magnitude, and never come to an end, but I see that is wrong. I also found it a bit hard to believe in a lepton with a positive mass at least 6 orders of magnitude less than an electron.
But now I see there are good reasons to believe the heaviest neutrino should have a mass around about 6 orders of magnitude less than electron. And if it is is excluded from having a mass in that range, then that shows there's something wrong with the theory.
I read the theory of neutrino oscillation depends upon differences in the square of the masses of neutrino flavours. We can estimate the difference of the sum of squares from the the oscillation characteristics. So that implies the heaviest flavour of neutrino should have a mass of at least 0.05eV/c2. But clearly the other flavours could weigh rather less.
Meanwhile, considerations from cosmology are suggesting an upper limit of 0.11eV/c2 - possibly that's an average of the flavours.
So there is a fairly narrow window to aim for, at least in terms of the mass of the heaviest neutrino. And you'll know something is wrong if they are strongly excluded from that window.
But maybe you don't have experimental methods of making measurements on all 3 neutrino flavours, so you can't necessarily determine the mass or speed of the heaviest type?
I thought this was going to be an unbounded game where we could just keep pushing it down a few more orders of magnitude, and never come to an end, but I see that is wrong. I also found it a bit hard to believe in a lepton with a positive mass at least 6 orders of magnitude less than an electron.
But now I see there are good reasons to believe the heaviest neutrino should have a mass around about 6 orders of magnitude less than electron. And if it is is excluded from having a mass in that range, then that shows there's something wrong with the theory.
I read the theory of neutrino oscillation depends upon differences in the square of the masses of neutrino flavours. We can estimate the difference of the sum of squares from the the oscillation characteristics. So that implies the heaviest flavour of neutrino should have a mass of at least 0.05eV/c2. But clearly the other flavours could weigh rather less.
Meanwhile, considerations from cosmology are suggesting an upper limit of 0.11eV/c2 - possibly that's an average of the flavours.
So there is a fairly narrow window to aim for, at least in terms of the mass of the heaviest neutrino. And you'll know something is wrong if they are strongly excluded from that window.
But maybe you don't have experimental methods of making measurements on all 3 neutrino flavours, so you can't necessarily determine the mass or speed of the heaviest type?
Re: Quantized Majorana conductance
AIUI neutrinos are in a superposition of three flavours and depending on when you observe one you get to see one of those three. But each of the three flavours have a different mass. What happens to conservation of mass? If you see it as an tau neutrino then later on as an electron neutrino, what happens to the missing mass? Same when it goes the other way, where does it get the mass from? Or does quantum mechanics manage to ignore that because quantum magic gets to over rule classical nonsense and involves maths way beyond what I’m now capable of?
Re: Quantized Majorana conductance
Mass can be exchanged for energy.bjn wrote: ↑Mon Jun 26, 2023 9:11 pmAIUI neutrinos are in a superposition of three flavours and depending on when you observe one you get to see one of those three. But each of the three flavours have a different mass. What happens to conservation of mass? If you see it as an tau neutrino then later on as an electron neutrino, what happens to the missing mass? Same when it goes the other way, where does it get the mass from? Or does quantum mechanics manage to ignore that because quantum magic gets to over rule classical nonsense and involves maths way beyond what I’m now capable of?
Re: Quantized Majorana conductance
I know that, so do they radiate/absorb energy or speed up/slow down when they flip between flavours? Or something else?dyqik wrote: ↑Mon Jun 26, 2023 9:23 pmMass can be exchanged for energy.bjn wrote: ↑Mon Jun 26, 2023 9:11 pmAIUI neutrinos are in a superposition of three flavours and depending on when you observe one you get to see one of those three. But each of the three flavours have a different mass. What happens to conservation of mass? If you see it as an tau neutrino then later on as an electron neutrino, what happens to the missing mass? Same when it goes the other way, where does it get the mass from? Or does quantum mechanics manage to ignore that because quantum magic gets to over rule classical nonsense and involves maths way beyond what I’m now capable of?
Re: Quantized Majorana conductance
They don't flip between flavors as they travel - they travel as a superposition of the flavors, which has a well defined mass/energy (and thus momentum). But the mass eigenstates aren't the same as the flavor eigenstates, so when a weak interaction with a neutrino happens, the mass eigenstate is reduced to a flavor eigenstate, with different probabilities for each flavor.bjn wrote: ↑Mon Jun 26, 2023 9:57 pmI know that, so do they radiate/absorb energy or speed up/slow down when they flip between flavours? Or something else?dyqik wrote: ↑Mon Jun 26, 2023 9:23 pmMass can be exchanged for energy.bjn wrote: ↑Mon Jun 26, 2023 9:11 pmAIUI neutrinos are in a superposition of three flavours and depending on when you observe one you get to see one of those three. But each of the three flavours have a different mass. What happens to conservation of mass? If you see it as an tau neutrino then later on as an electron neutrino, what happens to the missing mass? Same when it goes the other way, where does it get the mass from? Or does quantum mechanics manage to ignore that because quantum magic gets to over rule classical nonsense and involves maths way beyond what I’m now capable of?
The probability of a particular flavor eigenstate being the outcome of an interaction fluctuates as the phases of the flavor elements of the wavefunction of a mass eigenstate change with respect to one another.
Re: Quantized Majorana conductance
I read that a solar neutrino oscillates on average about once per 1250m. So unless you are detecting neutrinos from rather close to their source, it would seem "when" ceases to be a practical issue, as after a fairly short distance they will become fully randomised. Though maybe at higher energies the oscillation occurs over longer distances, due to greater time dilation, (he hand-waves in his ignorance). The 730km from Geneva to Gran Sasso seems to be enough for the muon-neutrinos emitted at CERN to oscillate to tau-neutrinos in detectable quantities.
The detection of tau-neutrinos in small numbers at Gran Sasso was news, so detecting these other flavours is possible but apparently not easy.
But we have just learned with thanks to dyqik that mass eigenstates are not aligned with flavour eigenstates. So that is implying we can straightforwardly detect the heavier/slower neutrinos in an experiment, because a fraction of the heavier mass eigenstates will interact as each of the flavours?
So is the sensitivity of this new experiment sufficient to close the window on neutrino mass?
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Re: Quantized Majorana conductance
There's a Pinned thread from CMTC about topological quantum computing, which is of course moot as long as the quasi particles they need to be able to do it don't exist.
Meanwhile there's work to induce superconductivity in semiconductors by putting them very close to metallic superconductors.
Meanwhile there's work to induce superconductivity in semiconductors by putting them very close to metallic superconductors.
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Quantized Majorana conductance
I'll bump this because there are posts relevant to the Q day thing, amongst the neutrinos.
having that swing is a necessary but not sufficient condition for it meaning a thing
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