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There exists a classical model of the photon after all
- cevn 12y ago"Updating this with modern knowledge of quantised magnetic flux, we show that if you model a flux tube as a phase vortex in an inviscid compressible fluid, then wavepackets sent down this vortex obey Maxwell’s equations to first order; that they can have linear or circular polarisation; and that the correlation measured between the polarisation of two cogenerated wavepackets is exactly the same as is predicted by quantum mechanics and measured in the Bell tests." How long would I have to study physics to be able to understand everything in this sentence?
- fdej 12y agoYou should be able to understand everything in that sentence if you have taken a typical undergraduate curriculum in physics including quantum mechanics and electromagnetism. Though it depends on what you mean by "understand". It should be clear what "quantised magnetic flux" is roughly about, but I have no idea what constitutes the "modern knowledge of quantised magnetic flux" in this context.
- sp332 12y agoThat doesn't help with the first part, about a phase vortex in compressible inviscous liquids.
- dkarapetyan 12y agoA lifetime, or long enough that it would feel like a lifetime. The real question to ask is that how you really want to spend your life? The fact that you're asking makes me think you've already chosen another path.
- maaku 12y agoIt does not take a lifetime. It took me about 6 months to cover upper-division electricity and magnetism and quantum mechanics, which is probably all that you would need to get the most basic but complete understanding of this paper.
- pbhjpbhj 12y agoClimbing to 20,000 ft from the 16,000 ft makes you think that climbing mountains is easier than it's going to be for the person at sea-level that you're advising. If you've been at 16,000 ft for some time even just that acclimatisation is going to make a huge difference.
- Iftheshoefits 12y agoJust about every concept (mathematical and physics) in the arXiv paper linked from the article is covered by the end of a typical undergraduate course in electromagnetism and quantum mechanics. The ones that aren't (specifically with respect to certain particulars of fluid dynamics and flux) are easily supplemented with material of the same depth and complexity (i.e. undergraduate level).
- jerf 12y agoTo really, really get it? The standard electromagnetism semester and a QM semester, both "for majors" (not the simplified general version), and something else for the "inviscid compressible fluid" (fluid dynamics, I assume, this might require some stuff that won't come up until semester 2, not sure), and a factor difficult to express in terms of semesters that you are not merely aping the mathematical results you are being taught by rote, but actually understand how to manipulate the math and follow deeply when you see other people do it. (Which I mean quite straight, not sarcastically.) I'm pretty sure this would all be accessible to an undergrad physics major who passes my math criterion above. It would probably be beyond them to do the work, but they should be able to follow it.
- rayiner 12y agoAn aerospace major who took a QM elective, or a physics major who took a couple of aerodynamics electives, would probably cover the necessary material by the end of year 2 of an undergraduate program. If you've got a solid, intuitive grasp of calculus and differential equations, you could probably learn enough from lecture notes to understand this in a few weeks. This is the most accessible physics paper that you'll ever see make the news.
- clavalle 12y agoIt can take a bit of unpacking, but someone with some sort of college level physics and mathematics background can use Wikipedia to get a basic understanding of what they are talking about. They are basically saying that the quantum mechanical 'strangeness' of light can be explained with classical, deterministic, physics. It is not necessary to have a separation in which quantum mechanics predominates at one level and trumps classical mechanics. It call all be understood as movement of 'particles' of light (photons) on an underlying wave. http://en.wikipedia.org/wiki/Magnetic_flux_quantum http://en.wikipedia.org/wiki/Magnetic_flux_quantum http://simple.wikipedia.org/wiki/Magnetic_flux http://simple.wikipedia.org/wiki/Magnetic_flux http://en.wikipedia.org/wiki/Flux_tube http://en.wikipedia.org/wiki/Flux_tube http://en.wikipedia.org/wiki/Quantum_vortex http://en.wikipedia.org/wiki/Quantum_vortex http://en.wikipedia.org/wiki/Wave_packet http://en.wikipedia.org/wiki/Wave_packet http://en.wikipedia.org/wiki/Maxwell%27s_equations http://en.wikipedia.org/wiki/Maxwell%27s_equations http://en.wikipedia.org/wiki/Differential_equation http://en.wikipedia.org/wiki/Differential_equation http://en.wikipedia.org/wiki/Polarization_%28waves%29 http://en.wikipedia.org/wiki/Polarization_%28waves%29 http://en.wikipedia.org/wiki/Bell_test_experiments http://en.wikipedia.org/wiki/Bell_test_experiments http://en.wikipedia.org/wiki/Fluid_dynamics http://en.wikipedia.org/wiki/Fluid_dynamics http://en.wikipedia.org/wiki/Pilot_wave http://en.wikipedia.org/wiki/Pilot_wave http://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory http://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory
- itistoday2 12y agoPilot wave theory has been known for decades. So can someone explain how whatever they're talking about is different/new?
- cgearhart 12y agoTheir central claim is that they found a specific instance of quantum behavior where they can represent the whole model with only classical mechanics rather than falling back on quantum explanations like wavefunction collapse, etc. We think that describing quantum systems requires quantum explanations, so finding a counterexample could be interesting.
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- sampo 12y ago> How long would I have to study physics to be able to understand everything in this sentence? Just start reading David J. Griffiths: Introduction to Electrodynamics. A very well written textbook. The problem might be, if you don't know vector calculus, you might not be able to read this book, so you need to learn some vector calculus, too. Then start reading Introduction to Quantum Mechanics by Griffiths, too. Best introductory QM book that I know of. If you managed to read Electrodynamics, you should by now know enough calculus for this book, too. But you also need to know about complex numbers here. The "inviscid compressible fluid" is about fluid mechanics. I don't know any splendid textbook on that.
- nilkn 12y agoI haven't read it, and it may be too advanced for this purpose, but Landau's books are generally held in extremely high regard and volume six of his Course of Theoretical Physics is on fluid mechanics. For what it's worth, volumes two and three cover electrodynamics and quantum mechanics, respectively.
- sampo 12y ago> Landau's books Landau's presentation is extremely condensed. Griffiths is much more friendly towards the reader. I would compare Landau to Knuth's The Art of Computer Programming. Some people do read them, but the rest of us just hold them in extremely high regard :-).
- jeffwass 12y agoThe Landau Lifshitz series is absolutely amazing. It works so well with my brain, entirely concise with just enough textual clarification as needed. Eg, volume 1 is classical mechanics. By page 3 or so you e already derived the Lagrangian equations of motion.
- jarvist 12y agoLandau/Lifshitz are freely available on the Internet archive: https://archive.org/search.php?query=creator%3A%22L.D.+Landau+%26+E.M.+Lifshitz%22 https://archive.org/search.php?query=creator%3A%22L.D.+Landa...
- angdis 12y agoIt depends on what you mean by "understand everything". That is a very terse, densely packed sentence of jargon intended for practitioners but a physicist who is a skilled communicator could describe the main results to a high school kid. To be able to fully understand the arguments leading to those results... it would take very serious study and decently sophisticated mathematical background before even starting.
- phkahler 12y agoI hope this is as awesome as it sounds. It sums up everything I've been thinking about quantum physics, from "someone should look closer at Couders work" to "spooky action at a distance is BS" to "Quantum computers will never work - see spooky action".
- sp332 12y agoSpooky action has been empirically demonstrated. https://arstechnica.com/science/2012/04/decision-to-entangle-effects-results-of-measurements-taken-beforehand/ https://arstechnica.com/science/2012/04/decision-to-entangle...
- phkahler 12y agoI call BS. If that's true, then Victor can not only send information across a distance, but back in time. Victor is changing the correlation of Alice and Bobs measurements after they have already been made. That's going to need serious verification for me to accept.
- john_b 12y agoOr you could just, you know, check the published experimental results: http://www.technologyreview.com/view/512281/chinese-physicists-measure-speed-of-spooky-action-at-a-distance/ http://www.technologyreview.com/view/512281/chinese-physicis... Physicists are increasingly convinced that time is an emergent property that arises due to low level quantum effects, principally entanglement [1]. The experiment in the Ars Technica article is the equivalent of the universe using lazy evaluation. It's really not so mysterious if you think outside the box of classical physics. Regarding sending information back in time, from what I've read physicists are divided on the issue. Most agree that sending matter back in time is impossible, but information is still up for debate. In this particular experiment, however, any past observer who measured the information sent back in time would have collapsed the entangled quantum state and prevented the experiment from being conducted successfully. So being able to "successfully" send information back in time doesn't appear too useful if you can't read it. [1] http://arxiv.org/abs/1310.4691 http://arxiv.org/abs/1310.4691
- yiyus 12y ago"our paper shows that the main empirical argument against classical models of reality is unsound.". That's quite an affirmation!
- Strilanc 12y agoScott Aaronson has commented negatively on a previous paper by the same authors [1]. I don't know if similar issues apply to this one: > [...] the paper advances the prediction that quantum computation will never be possible with more than 3 or 4 qubits. [...] I wonder: before uploading their paper, did the authors check whether their prediction was, y’know, already falsified? How do they reconcile their proposal with (for example) the 8-qubit entanglement observed by Haffner et al. with trapped ions [...] (Note: that's a critique of the previous paper, not the linked one. Although the linked post mentions quantum computers not working, the linked paper does not touch the subjet.) 1: http://www.scottaaronson.com/blog/?p=1255 http://www.scottaaronson.com/blog/?p=1255
- btilly 12y agoThey claim to have found a classical system that reproduces quantum mechanical effects. But if they manage to extend it to many particles, interacting, they will find that they have just come up with another interpretation of QM which is experimentally indistinguishable from the rest. And it wouldn't even be the first one. (Bohm's hidden variable theory has precedence.) Furthermore the "incompressible fluid" they postulate sounds like it enables non-local behavior (which it has to to match current versions of the Bell test) so it is unable to help resolve the issue of reconciling GM with QM. So this does rather less than they claim. Assuming that their claimed result is correct.
- fixermark 12y agoWhat's the current status of Bohm's hidden variable theory? Does it stand up in light of the Bell test (I was under the impression that the Bell results suggest an arbitrary number of hidden variables would be necessary)?
- btilly 12y agoI don't know and don't keep track. I lost interest after realizing that it can be made compatible with any possible observation. I'm personally a fan of the Everett interpretation. Also called the many worlds. Which is what you get if you assume that quantum mechanics applies to the observer. Then the act of observation throws the observer into a superposition of possible states where different things were observed. And those states cannot meaningfully interact later for thermodynamic reasons. Unless someone comes up with good reason to believe that quantum mechanics does not describe humans, I see no reason not to accept it. And if quantum mechanics is replaced by something different, to the extent that quantum mechanics is an accurate description of us, that interpretation remains correct.
- Dylan16807 12y ago>good reason to believe that quantum mechanics does not describe humans One simple idea is that the more energy and matter you shove into the wave function, the easier it is to collapse, so that at the macro level quantum effects are rendered impossible.
- taybin 12y ago"if the fundamental particles are just quasiparticles in a superfluid quantum vacuum" well obviously.
- tjradcliffe 12y agoThis paper has a variety of issues, the most glaring of which is that their "explanation" of the experimental violation of Bell's inequalities (specifically the CHSH form that has been realized in many experiments on polarization) is dependent on a static setup of precisely the kind that Aspect's experiments were intended to avoid. Aspect's work is one of the most beautiful pieces of careful and precise experimental testing of an idea in the past half-century, and while it has been attacked from many perspectives it is still a very robust argument for the non-locality of reality. One of the important things about it is that the polarization direction was switched in a quasi-random way after the photons had left the source. Variations on this trick have been performed since, and they all agree with the predictions of quantum theory. The authors say in this paper "The CHSH assumption is not true in Faraday's model. Instead there is prior communication of orientation along phase vortices such as(4), communication which the CHSH calculation excludes by its explicit assumption." In experiments like Aspects, prior communication is ruled out because the experimental setup is varied in one arm of the apparatus outside forward light cone of the other photon. Each photon gets detected before the other one could possibly know (based on signalling at the speed of light) what polarizer orientation it should be lined up with. So this is an interesting bit of work that might be useful in creating photonic quasi-particles in magnetic fluids that would allow for study of photon properties that might be difficult to get an experimental handle on otherwise, but the claim that they have a classical model that violates Bell's inequalities in a way that is relevant to the actual experimental work done in this area is considerably overblown.
- GregBuchholz 12y agoI'm not a physicist, but I've always wondered about Caroline Thompson's work, like: "Chaotic Ball" model, local realism and the Bell test loopholes http://arxiv.org/abs/quant-ph/0210150 http://arxiv.org/abs/quant-ph/0210150 ...any thoughts?
- tjradcliffe 12y agoThe scrutiny that Bell test experiments get from loophole people is always much appreciated, but the problem with Aspect's results in particular is that lovely parenthetical remark that appears in several of his figures, to the tune of "The dotted line is not a fit to the data, but the quantum mechanical prediction for this result." While it is easy to imagine selective-detection effects that mess up the results enough to invalidate the test at the level of the inequality, it is very, very difficult to maintain all the physics required for precise, detailed agreement between theory and experiment of the kind that Aspect and others have shown. Here is an example of a "local realistic model" that reproduces the quantum mechanical results for in-time coincidences, but completely messes up any number of auxiliary measurements: http://www.tjradcliffe.com/?p=590 http://www.tjradcliffe.com/?p=590 So while I'd love to see a modern version of Aspect's work using state-of-the-art entangled photon sources and the like, the likely reason it hasn't been done is that the odds of it revealing anything new and different are trivially small (but not zero, of course!)
- vilhelm_s 12y agoI don't know any physics, but it seems like a bit of a warning sign that these new discoveries in fundamental physics are annouced on... a computer security blog?
- nilkn 12y agoWhen models like this are proposed, a lot of people are interested because of the philosophical implications of a classical theory of quantum phenomena. The question I have, though, is this: does this model actually help model phenomena that we can't already model? Quantum gravity is the big spectacular example, but there are many others. For instance, the Standard Model is very successful at predicting the anomalous magnetic moment of the electron. But it is not successful at predicting the same quantity for the muon. There are many other issues with the Standard Model that aren't so high-flung as quantum gravity. Are classical models like these, if they can be shown to incorporate multiple particles interacting simultaneously, capable of going beyond the Standard Model or merely replicating it?
- snarfy 12y ago> Updating this with modern knowledge of quantised magnetic flux It sounds like they are using quantum mechanics to explain quantum mechanics.