Nobel Prize in Physics Awarded to Alain Aspect, John Clauser and Anton Zeilinger
nobelprize.org
nobelprize.org
He certainly deserves it. He is incredible experimentalist:
- Macroscopic quantum inference with molecules like C70.
- two photon orbital angular momentum entanglement with 600 difference in quantum number.
- multi-particle entangement.
- quantum teleportation
Cosmic Bell Test using Random Measurement Settings from High-Redshift Quasars (2018) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12... > .. This experiment pushes back to at least ∼7.8 Gyr ago the most recent time by which any local-realist influences could have exploited the “freedom-of-choice” loophole to engineer the observed Bell violation, excluding any such mechanism from 96% of the space-time volume of the past light cone of our experiment, extending from the big bang to today.
Challenging local realism with human choices https://www.nature.com/articles/s41586-018-0085-3
>Bell himself noted this weakness in using physical setting choices and argued that human ‘free will’ could be used rigorously to ensure unpredictability in Bell tests8. Here we report a set of local-realism tests using human choices, which avoids assumptions about predictability in physics. We recruited about 100,000 human participants to play an online video game that incentivizes fast, sustained input of unpredictable selections and illustrates Bell-test methodology
>... Project outcomes include closing the ‘freedom-of-choice loophole’ (the possibility that the setting choices are influenced by ‘hidden variables’ to correlate with the particle properties
Please don't flame me if this is an outrageous question, because I readily admit I know nothing on the topic of quantum physics, but isn't it a quite large limitation to assume human free will as a given? Or is "free-will" meant as a proxy for "pseudo-random" and that's enough for this experiment?
It has to do with true randomness in the measurement aspect, not with human free will.
Edit: I'm normally not one to complain about well deserved downvotes, but I think people may be missing my joking tone, and context here. Once a few people that also know Clauser give thoughtful replies in this discussion, it will make more sense.
Can you explain what you mean by this?
Winston Churchill is the similar … remembered as a political leader, but won the Nobel in Literature, not Peace.
Einsteins Nobel was for Brownian motion, which isn’t what pops to mind when you think “Einstein.”
"for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect"
"…it comes as a relief to be reminded of your insignificance: it’s the feeling of realizing that you’d been holding yourself, all this time, to standards you couldn’t reasonably be expected to meet. And this realization isn’t merely calming but liberating, because once you’re no longer burdened by such an unrealistic definition of a “life well spent,” you’re freed to consider the possibility that a far wider variety of things might qualify as meaningful ways to use your finite time. You’re freed, too, to consider the possibility that many of the things you’re already doing with it are more meaningful than you’d supposed—and that until now, you’d subconsciously been devaluing them, on the grounds that they weren’t “significant” enough. (Burkeman 2021, p 212)"
> The Total Perspective Vortex derives its picture of the whole Universe on the principle of extrapolated matter analyses.
> To explain — since every piece of matter in the Universe is in some way affected by every other piece of matter in the Universe, it is in theory possible to extrapolate the whole of creation — every sun, every planet, their orbits, their composition and their economic and social history from, say, one small piece of fairy cake.
> The man who invented the Total Perspective Vortex did so basically in order to annoy his wife.
> Trin Tragula — for that was his name — was a dreamer, a thinker, a speculative philosopher or, as his wife would have it, an idiot.
> And she would nag him incessantly about the utterly inordinate amount of time he spent staring out into space, or mulling over the mechanics of safety pins, or doing spectrographic analyses of pieces of fairy cake.
> “Have some sense of proportion!” she would say, sometimes as often as thirty-eight times in a single day.
> And so he built the Total Perspective Vortex — just to show her.
> And into one end he plugged the whole of reality as extrapolated from a piece of fairy cake, and into the other end he plugged his wife: so that when he turned it on she saw in one instant the whole infinity of creation and herself in relation to it.
> To Trin Tragula’s horror, the shock completely annihilated her brain; but to his satisfaction he realized that he had proved conclusively that if life is going to exist in a Universe of this size, then the one thing it cannot afford to have is a sense of proportion.
- Douglas Adams, Hitchhiker's Guide to the Galaxy
I was bewildered to see a blunder of that magnitude in the official nobel presentation...
>The Nobel Committee makes a common mistake in the press release, implying that Bell rules out hidden variables. It's only local hidden variables that are ruled out (absent superdeterminism). Bell was a big supporter of Bohmian non-local hidden variables!
from Sean Carroll https://twitter.com/seanmcarroll/status/1577254806208798722
Bell on Bohm - Sheldon Goldstein - https://sites.math.rutgers.edu/~oldstein/papers/bb.pdf
Enjoy!
Also here for a bit of history: https://en.wikipedia.org/wiki/Bell_test
Popular science background: How entanglement has become a powerful tool (pdf)
Scientific Background: “For experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science” (pdf)
From a Quantum Computing perspective entanglement ist kind of overrated.
Scott Aaronson: How Much Structure Is Needed for Huge Quantum Speedups?
https://arxiv.org/pdf/2209.06930.pdf
Actually entanglement is not mentioned at all.
This is just a computational Perspective.
Gottesman-Knill Theorem:
"The theorem proves that, for all quantum algorithms with a speed up that relies on entanglement which can be achieved with a CNOT and a Hadamard gate to produce entangled states, this kind of entanglement alone does not give any computing advantage."
Entanglement alone is not sufficient for algorithmic speedup.
Again Wikipedia:
"The reason for the speed up of quantum computers is not yet fully understood"
(1) the dimension of the Tensorproduct Space of n entangled Qubits is 2^n.
(2) exponential speedup
but which?
Have I understood it correctly?
About probability: no one knows. It might be that there is a "wave function collapse" that has a probabilistic outcome. But it might be that there is no such a thing. Quantum mechanics that remain in the "quantum" realm are not probabilistic, it's only when you cross over to the classical world.
So it might be equally well, that the Everett interpretation (so-called "many worlds interpretation") is true, and the probability is something physicist Sean Carroll calls "self-locating uncertainty": https://www.preposterousuniverse.com/blog/2014/07/24/why-pro... That is, there are multiple "yous" that experience different outcomes, and you don't know which branch of the wavefunction you find "yourself" in, which "you" you are.
That's not true. The only thing we know is that the above appears to be true, but since we do not actually know the mechanism behind quantum mechanics we will be in this limbo until (if ever) we find the actual rules.
I do have a small gripe with the above comment, in that Bell's theorem only rules out local hidden variables. Some take the view that Bohmian mechanics is an formulation of quantum theory which employs hidden variables, just explicitly non-local ones.
Superdeterminism also allows local hidden variable theory without violating Bell's theorem:
> https://en.wikipedia.org/wiki/Superdeterminism
A 2013 interview with the Nobel Laureate Gerard 't Hooft on this topic:
> https://spookyactionbook.com/2013/10/07/does-some-deeper-lev...
A paper by Sabine Hossenfelder and Tim Palmer:
Sabine Hossenfelder and Tim Palmer; Rethinking Superdeterminism
> https://www.frontiersin.org/articles/10.3389/fphy.2020.00139...
In 2016, 't Hooft published a textbook on some specific points of superdeterminism:
Gerard 't Hooft; The Cellular Automaton Interpretation of Quantum Mechanics
Sabine Hossenfelder and Tim Palmer; Rethinking Superdeterminism
> https://www.frontiersin.org/articles/10.3389/fphy.2020.00139...
I mean, this is the crux of it. You'd have to have some convincing way of explaining why states "give rise to the predictions of quantum mechanics" for all possible measurement choices yet to be made by anyone. It still feels conspiratorial to me, having read that whole section! If someone were to show me a simple mathematical expression as defined above, I would be open to it. As far as I can tell, all this article is saying is "maybe it's possible".
Finding such a simple mathematical expression is exactly what research into this direction is for. But obtaining such is rather the end result that one hopes for.
... as long as we assume that the system being measured is uncorrelated with the choices of which measurements to make on it. :-)
"To be more precise, what we shall show is that the particles’ response∗ to a certain type of experiment is not determined by the entire previous history of that part of the universe accessible to them."
John Conway, Simon Kochen: Free Will Theorem https://arxiv.org/abs/quant-ph/0604079
Always keep in mind that Bell himself was quite a fan of Bohm's theory, which is the canonical hidden variable theory really. The question becomes one of characterising that 'strangeness': is it the violation of locality ('that part of the universe accessible to them'), is violating outcome independence palatable, but not parameter independence (this was Shimony's idea originally)? Lots of curious stuff.
> We consider experimenters A and B performing the pair of experiments described in the TWIN axiom on separated twinned particles a and b, and assert that the responses of a and b cannot be functions of all the information available to them.
I don’t get it — this sounds like they assumed their conclusion.
There’s also a couple places they make strong assumptions about information geometry I’m not sure I agree with — namely, if you want to refute modern Bohm-inspired models, you need to account for radically non-Euclidean spacetime. (Where you have a much harder time with “space like separated”.)
> FIN is not experimentally verifiable directly, even in principle (unlike SPIN and TWIN3).Its real justification is that it follows from relativity and what we call “effective causality,” that effects cannot precede their causes. […]
> Not all information in the universe is accessible to a particle a. In the light of FIN, information that is space–like separated from a is not accessible to a. The information that is accessible to a is the information in the past light cone of a.
That is why there was a lot of interest in doing cosmic Bell-like experiments: it is very hard to define a mechanism whereby the hidden property of the particle that left the quasar many billions of years ago also determined that Alice and Bob would set their apparatuses to measure these specific angles today. Theoretically this doesn't rule out the possibility, but it does mean at least that the theory would have to be significantly non-intuitive in its own right (whereas if Bell-like inequalities only happened for small-scale experiment, the theory that explained them could have been very simple indeed - such as some new wave that affected the measurement apparatus or some aspect of how we choose measurement angles).
The exact alternative to non-determinism is super-macro quasiparticles/correlations. Which this seems to assume away.
To take it to a more human realm - we can all agree that if Caesar weren't killed by Brutus, the world would be so different that it's very unlikely both Biden and Putin would be presidents of their respective countries today - this is an almost trivially true statement I would argue. However, if we observe that at every public appearance Biden and Putin wear costumes of the same color, it's very hard to come up with a theory that explains that their choice of costume is caused by Caesar killing Brutus.
And this is essentially what the super-determinism argument gets at: the same thing that caused this photon emitted by a quark to be polarized up 1 billion years after the Big Bang also caused Alice to measure the polarization of that particle along 30 degrees 13 billion years after the Big Bang.
Eg, that particle being a particular state is correlated to Alice picking a particular measurement because the total system must maintain that quantum number. The particle which emitted the photon and the particles which give way to Alice have carried that information since the inflationary period — and so the photon and Alice share that correlation now.
The conclusion seems to be “the correlation must be at least this old!” — but that’s exactly the claim being made.
So I’m not sure I understand the problem for Bohm-derived models.
Also, not sure what particular quantum number you think would have to be conserved and would influence Alice's decision of which way to configure her measurement apparatus - this would definitely require some new quantum property.
Aspect et al demonstrated experimentally that quantum mechanics is correct in the Bell sense.
As mentioned elsewhere, their work is the foundation of quantum computing and quantum cryptography, which probably hasn’t directly affected your life yet but could very well do so in a not-too-far future. Again, entirely unlike string theory.
We are currently where computing was in the 1900s: critical innovations like transistors and ICs have not happened yet, but the concept of computers is much older than that, with examples such as Babbage’s analytical engine or Pascal’s calculator.
Edit: Sabine Hossenfelder has explained this much better than I ever can: See for example http://backreaction.blogspot.com/2021/12/does-superdetermini...
The requirement that you can encode Turing machines might sound silly but I really think it's the core of the issue. The ability to make computers implies a certain level of hard-to-control due to the existence of things like the halting problem and pseudo random number generators and cryptographic hash functions.
My understanding is that super determinism is one of those loopholes where it's easy to say its a problem, but actually providung a plausible concrete model where it's a problem is very hard.
I am not aware that such a theory exists, but the Nobel laureate Gerard 't Hooft made some possible first baby steps into this direction:
Gerard 't Hooft; The Cellular Automaton Interpretation of Quantum Mechanics
However, sometimes, people do think about Turing Machines. Here is one paper by Scott Aaronson http://www.scottaaronson.com/papers/ctchalt.pdf
But this doesn't make it wrong. Superdeterminism is a very neat way of resolving physical paradoxes, such as the Wigner's Friend paradox: Any experimenter’s decision to take a measurement of a certain physical phenomenon is predetermined by events, so the experimenter can attain no outcome but the one he does eventually attain, and nothing is in superposition. Neither Heisenberg's uncertainty principle nor Bell's inequality render this condition impossible, as Bell himself was well aware.
The same objection can be stated for the many-worlds interpretation of quantum mechanics:
I rather think the same standard should be applied to both.
It's sort of like constructivist mathematics in that it involves dropping an extremely useful axiom, and then rederives basically all the same results in a more roundabout way.
https://www.quantamagazine.org/why-the-many-worlds-interpret...
"Attempts to explain the appearance of probability within the MWI come down to saying that quantum probabilities are just what quantum mechanics looks like when consciousness is restricted to only one world. [...] What the MWI really denies is the existence of facts at all. It replaces them with an experience of pseudo-facts (we think that this happened, even though that happened too). In so doing, it eliminates any coherent notion of what we can experience, or have experienced, or are experiencing right now. We might reasonably wonder if there is any value — any meaning — in what remains, and whether the sacrifice has been worth it."
That quote is simply wrong when it says that MWI "restricts consciousness to one world". As a simple matter of calculation, you can work out what MWI predicts a complex agent will report as its experience. Here for complex agent I want you to picture a computer program recording events and accumulating statistics, not a person, just because it makes the thinking clearer. Anyways, the prediction is that the recordings will be consistent with a classical type view, for lack of a better word, as opposed to a superposition of experiences. Even if the computer program was in fact run in superposition and interacted with superposed objects.
But this is not surprising, because we already know that all the interpretations of quantum mechanics give the same predictions. So of course many worlds is not going to disagree with collapse type theories on what people say they experience. Because it is mathematically equivalent to the others. Observationally indistinguishable.
Edit: where does the MWI define “complex agent” and “experience”, by the way? I thought that MWI was precisely defined by assuming the postulates of quantum mechanics without including the Born rule, but it seems that there may be more to it!
By Occam's Razor, if there exist multiple theories that are indistinguishable, we should take the one that has minimal assumptions (i.e. no assumption of the existence of some "multiverse" like in the many worlds interpretation).
There's kind of an ontological trick at this point. Using decoherence, self-locating uncertainty, and one or more assumptions about rational decision-making, you can derive what rational credence you might apportion to each of the agent's possible experiences. I feel like this is different from actually predicting the agent's experience.
Those questions do not seem easier to answer than “what’s a measurement”.
Which suddenly sounds a lot like QBism.
Every interpretation of quantum mechanics is utterly untestable, or more precisely, each one is exactly as testable as every other interpretation because they all explain the data equally. That's why they're "interpretations".
This may (or may not) change with work by Gerard t'Hooft and others.
Other such assumptions that would allow local hidden variable theories are "a wizard did it" and the rejection of the principle of relativity. All three share that they have no convincing reasoning behind them and that they are largely incompatible with our model of falsifiable science.
Don't get me wrong, they are all great experimentalists and their experimental work helped move the science forward in the understanding and control of the atomic scale.
But their "Bell's experiment" variations have been used to "disprove" and cast aside wide branches of theoretical research, and this will probably remain as one of the biggest failure of modern science.
If you model the experimental settings in your theory, it's indeed quite simple to reproduce the QM probabilities (and therefore violations of CHSH inegalities), with a local hidden variable theory.
In fact here is 60 lines of numpy code to set-up virtual experiments to convince yourself (try various settings for the polarisers angles alpha and beta) https://gist.github.com/unrealwill/2a48ea0926deac4011d268426... (Straight implementation of Marian Kupczynski "Closing the Door on Quantum Nonlocality" https://www.mdpi.com/1099-4300/20/11/877 (around eq.7-8) if you need more explanation).
This is not the whole truth. Bell's inequality assumes a few reasonable assumptions for hidden variable theories besides locality (https://plato.stanford.edu/entries/bell-theorem/) and it is true that sacrificing these assumptions can yield a local hidden theory consistent with Bell's inequality / CHSH inequality violations.
But the whole point of these assumptions is that we want them. Bell's inequality is the definitive experimental test that a standard classical theory is not waiting in the wings for us, and those assumptions are central to classical mechanics.
The issue with a theory that sacrifices things like parameter independence or similar is that they will remain mathematical curiosities, much like interpretations of quantum mechanics, because there is no way to test them. And they'd be stranger than quantum mechanics, so you don't get any relief either.
So, yes, you can do this. But it has no practical value. This is not the experiment's fault in any way.
However, if you are arguing that you can have a local hidden variable theory that satisfies all of Bell's assumptions and violates the inequality, then you have some severe issues in your argument somewhere, because it is categorically impossible.
> 60 lines of numpy code
In the event you are arguing for a local hidden variable theory that satisfies all of Bell's other criteria: firstly, there is no guarantee the simulation has any fidelity to the real world at all.
Thankfully, you don't have to settle for simulation. I was fortunate to take 180Q at UCLA, an undergraduate class where we were required to derive the CHSH inequality and perform simple experimental violations by ourselves. The tools needed to run a simple test are commercially available and affordable - you can do it yourself at home.
I was able to achieve experimental violation when I did so back in 2015/2016, and documented the results here:
https://github.com/AkshatM/Physics180Q/blob/master/Final%20P...
Of course, if you are arguing we can sacrifice an assumption of Bell's besides locality, then the above is moot. But it would still be rather pointless.
https://algassert.com/quantum/2015/10/11/Bell-Tests-vs-No-Co...
It's not hiding anything. It works because of the post-selection. But this selection is done in a locally compatible way.
It works because you as the (virtual) experimenter can specify/choose explicitly a precise definition of what a measurement is, (which you can't do in your widget).
My code is showing an example of the general structure of how you could/should define what a measurement is, in such a way that you preserve both the locality of the world, and the observed violation of the Bell inequalities (according to your definition of what a measurement is).
I'd argue that it's in essence doing what, one way or the other, the real world measurement apparatuses of the experimenters are doing.