Einstein-Bohr debate settled once and for all
scottaaronson.blog
scottaaronson.blog
This paper points out some of the most basic, paradigm shifting implications of entanglement and concludes, not that reality is truly this strange, but that the strangeness of these implications indicate the theory is incomplete. To be completely fair to Einstein, even if he had come up with Bell's inequalities at the time of writing this paper, they still would not have been possible to test with the technology of the day.
There is absolutely nothing to scoff at here. It may be wrong in it's conclusion, but the way in which it is wrong changed the course of physics. This is an example of how genius lies in asking the right questions even if you get the wrong answers. The EPR paradox remains a stunningly brilliant paper that should be closely ready by anyone in quantum physics.
Einstein was wrong, but in the most illuminating way possible!
I think that is the crux of the issue, we have waves with a discrete energy, we can call them particles but they are very different from the traditional image that people have of what a particle is.
On the other hand, try grab a part of an electron cloud around an atom and you will either get the entire electron or you will grab nothing. No matter what you do you can't separate one part of the cloud from the other, they are always connected. Trying to grab the electron will either remove all of the wave parts outside, or remove all of the wave part you try to grab. There is no classical system that behaves like this.
iirc, particles are actually excitations in a quantum field. the more particle-y an electron looks - the closer you bound its position - the more waves are needed to constructively/destructively interfere to make a peak there.
it's like a Fourier transform - if you want a perfect square wave you need infinite sine waves. in this analogy that's momentum space expanding out.
also, like, you're not really seeing individual electrons. you're seeing macroscopic phenomena, like your sensor or photomultiplier tube or whatever. you're seeing the interaction, not the particle. understanding that as your lab equipment, retina and brain entering the state space caused by resolving a wave to a spike makes more sense to me than some decoherence mechanism.
As for the electron, it is an oscillator described by a wave function, quantized, without locality. Here is an image of the wave function interpreted as a probability density:
https://en.wikipedia.org/wiki/Electron#/media/File:Hydrogen_...
The Quantum Mechanics interpretation is that the electron is a particle in an indeterminate location and the plot describes the probability of where the electron can be located. The Quantum Field Theory interpretation is that what we see is a field in an excited state, quantized. By looking at those plots, we can see a quantized field vibrating. If we send it through a double slit, it will behave like a wave. If instead we think about it as a single, indivisible particle, then we need to explain how it passes through two different slits at the same time. Thinking about it as a quantized oscillator disolves the paradox.
At that point of measurement/detection we HAVE to start talking about probabilities, not just waves, right?
Certainly, to me it feels like saying 'it is just a wave' doesn't describe it because this quantization is a special thing.
You can easily count individual photons, electrons, etc in an undergrad physics lab. How do you think that's possible with fields alone?
There's an interest in particles because there is no way to measure fields directly and the output of QFT is a set of particle-like probabilities.
This is not a trivial problem, QFT is not a trivial solution to it, and the paradoxes really haven't gone away.
You can count individual quanta of any kind (photons, electrons, etc.), and you can measure their quantum collapse. But that does not mean they are localized "particles" the way Dirac liked to think about them.
No. There is no way to discern a collapsed wave function from a non collapsed one, if that's what you mean.
This works since rotations aren't linear, small rotations are quadratic and hence will almost always result in the original state. You can also use this technique to rotate a state by making many measurements slowly changing the axis, so each measurement results in a small rotation.
Edit: But you are right that we can't see the history of state collapses, but they are definitely required for our current theories to work as you get the wrong experimental results without them in the theory.
But then following your prior reasoning, that's just another collapse. So if the only way to measure is to collapse then pmkahler is right: there is no way to discern a collapsed wave function from a non collapsed one.
But it isn't random, if we know how fast it rotates then the second time we measure it we can get a close to exact result.
The most famous experiment for this is the double slit experiment. Normally when you fire particles through you will get an interference pattern on the other side since the particles passes through like a wave. Measuring it in one will collapse the wavefunction and therefore destroying the inference pattern, so now the particles mostly just travels straight and creates a distribution of hits as if it passed through just a single slit.
Edit: Can look at this picture from wikipedia showing the difference between single and double slit, just measuring at one of the slits will even cause particles passing through the other slit to go much straighter.
https://upload.wikimedia.org/wikipedia/commons/c/c2/Single_s...
No. If you shoot pairs of entangled particles in opposite directions, someone receiving one stream of particles can take or not take measurements thereby collapsing or not collapsing the wave function of the particles going in the other direction. If you could tell the difference between a particle with a collapsed wave function and one without, this could be used for FLT communication. Bottom line is we can't tell if a wave function is "collapsed" or not. It's not a real event.
Yet, it's just twisting fields together.
The right picture to have is fermions being something like knots on a rope, in a portion of space either you have a knot or you don't. But the knot can be more or less tight, and can be moving and have various shape.
When the fields are not coupled, i.e. when particles are far away, the only stable solutions, have a discrete quantity. These quantities are the conserved quantities that are preserved by the field evolution. Typically they are the quadratic values that the symplectic integrator conserve locally.
When particles get closer, they can exchange continuously some of the quantities between their fields, but as in a game of musical chair, as soon as the particles get away from each other, they must have taken a seat and settled in one of their discrete values.
QFT or quantum physics is like keeping track of the counts of the number of knots on the ropes and model the probabilities of how these values evolve upon collisions. But if you keep track of the rope shape (aka fields phases), you can more precisely predict where the knots are.
The catch-22 is that the rope shape is not observable, (in a similar fashion as you can't observe the seed of a random number generator), so you can't make better prediction using the rope model than you could with quantum mechanic.
But the "answer" to this catch-22, is that even though with rope mechanics you can't compute the probabilities any faster than QM would (as marginalization isn't fast), you can simulate in same compute complexity as classical system a universe that behaves according (convergence in law) to the probabilities of QM.
“Switching from a particle-centric theory (like Quantum Mechanics) to a field-centric theory makes all the QM paradoxes disappear, and problems like locality, the double-slit experiment, etc., become trivial.“
I feel the same way. Would you know of any references that described the actual experiments seemingly revealing the paradoxes from quantum field theory perspective? Would appreciate it if you could share the references. Thanks!
For example, one of the arguments against Einstein's view was that Einstein's formulation implied that electrons in an excited atomic orbital would never decay. This, of course, is quite problematic as we know that electrons in atoms always decay.
Except that they don't!
When we put individual excited atoms in modern laser traps, we find that they don't drop from their excited state at the same rate. And the better the isolation, the slower that decay occurs. Whoops.
So, the problem is that these two greats were arguing with each other when a whole lot of the experimental evidence was still quite shaky and sometimes even wrong.
I'm asking because I read an article a while ago about some advances in higher-dimensional math that turned out to simplify certain quantum mechanical computations [1]. And it got my hopes up that we might eventually see quantum mechanics explained this way - e.g. as a projection/cross-section of higher dimensional phenomena into our 3D/4D reality. That the "weirdness" of QM could be explained by the effects happening in higher dimensional space. But from our perspective those would be hidden variables, so I'm curious whether we've been able to rule those out completely, or only partially?
[1] https://www.quantamagazine.org/physicists-discover-geometry-...
Local hidden variables can not explain experimental results of QM. That's a fact. Ask any QM Physicist and you'll get the same answer.
So, another way to say it is local hidden variables do explain experimental results of QM if you are willing to accept the implications, none of which contradict observation.
But why stick to LHV if you are willing to accept nonsense? There are infinitely many ways to accept nonsense without LHV!
There is this essentially religious notion of "free will" that physical theories have been obliged to preserve, for no objective reason. Hidden variables are inconsistent with experiment only if you demand "free will" be preserved.
No. Local hidden variables can't explain QM without breaking math or conflicting with very well tested experiments.
It isn't just "unfashionable".
You're free to postulate non-local hidden variables, but you can't wave away the EPR results like they're just philosophy.
Always omitted from the list of interpretations are those abandoning will-o-th-wisp "free will".
But we know for sure if it's fairies (or any other hidden variables) - they have to conspire globally. Cause otherways the experimental results couldn't happen the way they did cause fairies in place X wouldn't know which way to nudge the results to be consistent with the way fairies in place Y nudged them.
This is false information and even Bell himself knew it:
"There is a way to escape the inference of superluminal speeds and spooky action at a distance. But it involves absolute determinism in the universe, the complete absence of free will."
"Explicit construction of Local Hidden Variables for any quantum theory up to any desired accuracy"
https://arxiv.org/abs/2103.04335
Regarding unfalsifiable, from [0] "If engineers ever succeed in making such quantum computers, it seems to me that the CAT is falsified; no classical theory can explain quantum mechanics." By "such quantum computers" he means computers that can run Shor's algorithm. "...but factoring a number with millions of digits into its prime factors will not be possible – unless fundamentally improved classical algorithms turn out to exist."
[0] - https://arxiv.org/abs/1405.1548
Now, this does not mean these theories are ready, but they are being worked on.
https://arxiv.org/abs/2103.04335
Or right in the page I linked: "This makes it possible to construct a local hidden-variable theory that reproduces the predictions of quantum mechanics, for which a few toy models have been proposed."
By assuming superdeterminism you can indeed construct a valid local hidden variable theory. But there is no way you can say superdeterminism is by itself a local theory, and no physicts will call it so. It's as far from "local" theory as possible, it's actually global.
It reads like some sort of religious objection. If the data leads you there, you go there.
Sabine, particularly, goes there. Apparently there are no actual problems with giving up the illusion of "free will", whatever the hell it was supposed to mean in the first place.
Distaste seems pretty rich coming from people promoting MWI.
1. The wavefunction is non-local, it contains non-local entanglements. Many-worlds even says it describes the whole world.
2. The wavefunction cannot be directly observed.
3. Many worlds interpretation doesn't have a notion of collapse - there is no randomness.
So if you think about it, MWI is a deterministic global hidden variable theory. I have no idea how I didn't see it until now.
It's like the parable of the five blind men who encounter an elephant.
It’s not like that, because Bohr and Einstein looked at the same empirical evidence.
This is essentially my point. We all have access to the same set of data, but we all look at it a little differently.
But I'm curious to hear physicists' takes on this! e.g., the implausibility claim in the Wikipedia article would seem like a compelling rebuttal, except that I don't see why I should believe superdeterminism to be an implausible explanation at all. If anything, it sounds like the most plausible explanation we have—either that, or the Big Bang somehow doesn't imply superdeterminism (how is that even possible?), or the Big Bang theory is bogus to begin with.
Or if you prefer to think of balls; if A hits B, and then B hits C, then C's future trajectory is still (forever) affected by what A was doing, as is the trajectory of anything else it hits.
Saying 'everything is entangled' might not be that meaningful if the entanglement is random. If you want to get to super-determinism then it takes some very weird 'knowledge' in the entanglement. Rather than the entaglement being random.
Almost everything we interact with has this concentrated wave function. And when you see something without this concentration the process of how it 'decoheres' is chaotic. It just turns out that the chance of concentrating in a spot is proportional to the wave self-conjugation.
I could imagine the idea 'almost everything is engangled' meaning the chaotic nature of this concentration process is essentially perfectly random. Since you'd be interacting with trillions of other waves.
My point is that the evolution of the waveform is deterministic. Waveform collapse is where lots of theories introduce indeterminism. I propose a theory in which waveform collapse is technically deterministic.
My proposition is that the process is deterministic but chaotic. With the simultaneous state of all other particles determining how this collapse happens. Making it deterministic, but truly impossible to predict without a picture perfect representation of the outcome.
People interested in those questions might like some of the more recent looks at QM that are based on information theory. Zeilinger has an approach based on the idea that various aspects of particles can only have one bit of information.
From this he's able to derive entanglement, the uncertainty principle, the Schrödinger equation, and more.
PBS Space Time did an episode on this just over a month ago [1].
Einstein, Podolsky and Rosen put the argument into mathematically solid and testable form. Einstein really 'wins' the argument in my mind either way it turns out because his name is attached to the actual experiment you can run to try to settle the question.
He also got the Nobel prize for the photoelectric effect and directly helped to invent quantum mechanics. The idea that there's this Einstein-vs-QM WWE event is sort of false. He'd probably be more or less happy with the way things turned out since quantum observation can't be used for superluminal communication. It turns out QM is nonlocal, but it still has rules.
If Einstein had lived to 143+ and was still around it might be interesting to ask where we'd be, since I don't think he would have accepted the just sort of shrug-and-accept-it-MWI approach to quantum observation. He'd probably be busy with something like twistor theory and trying to turn matter into tiny wormholes in space-time that can stretch and break and produce QM.
Things that have big question marks, related to this debate:
- how do we mesh quantum with gravity?
- why do tangles cause quasiparticles?
- does tangling rescue geons?
One theory is that quantum mechanics is an approximation of tangles in a higher dimensional space when viewed as pseudoknots, in the style of AdS/CFT.
https://en.wikipedia.org/wiki/Tangle_(mathematics)
Which impacts dynamics/effects in various systems.
https://en.wikipedia.org/wiki/Anyon
Yeah, it can a useful ruler as a way to map changes; it's as real as a 'cubit', but not the territory. Energies may suffice. Things are constantly changing ... but only, and forever, Now. Without time, entanglement's no surprise.
Presentation, https://youtu.be/Z7rd04KzLcg
for the more educated - how "crackpot" is Weinstein? I have trouble assessing how full of himself he obviously is vs how much of a genius he also is.
Regarding the theory. It is is impossible to me to analyze his work, because it is impenetrable. What is a two-tensor, gauge theory, I for one have absolutely no idea. I think this is an Achilles heel of his approach, he needs to convey meaning better. Or maybe that's just how a theory of everything is articulated.
I much prefer Benjamin Disraeli's "All is mystery; but he is a slave who will not struggle to penetrate the dark veil."
My takeaway from this article as a nonphysicist was that it’s satire.
I can really recommend this book: "Dance of the Photons: From Einstein to Quantum Teleportation" by Anton Zeilinger. I read it when I was 16 and it's easy to read, but might shake to the foundations your understanding of the universe (as it did with mine). It clearly lays out why the position you take in your post is hard to maintain given some very simple experiments, even though your position looks so intuitive.
If not, this video gives a quick sketch of the argument and the experiment: https://youtu.be/f72whGQ31Wg?t=361
What does it mean to understand something?
You could argue understanding is just as much a human invention as math is.
"Reality" (if there is such a thing) is independent of anything the human mind comes up with (whether that's understanding, math, or something else).... or is it?