hi all. not too busy around here with other stuff at moment so am banging together this post on QM physics with a lot of recently accrued refs/ angles (the cup runneth over).

QM physics is an occasional topic around here mainly wrt quantum computing which was big in the news last year with DWaves computers newly run through paces by independent scientists and the Martinis lab buyout by Google.

one of the earliest topics on this blog was soliton theory meshing with QM physics theory (~2yr old post early 2013, “solitons/ CAs, QM and disagreeing with Aaronson”).

there is a constant dribble of news articles on (a) quantum computing advancements [m] and (b) somewhat strange, boundary-touching quantum computing experiments that at times seem to push the limits of the theory.

this reminds me of a historical period at the time of the multiple einsteinian revolutions. the original QM revolution was driven largely by new experimental results. we might be seeing the early hints/ glimmers of new experimental measurements that are not easily explained within the QM framework. ❓ 💡 ❗ 😮

the big inspiration for this post was meeting a new cyber-cohort Thomas Klimpel (TK) who turns out to be a very shrewd expert on quantum theory and its relationship with semiclassical theories, and has been exploring it in depth.[a17] his wideranging theoretical knowledge is apparently underpinned by a lot of practical work in chip photolithography for his day job where he wondered about the strong correspondences between applied semiclassical and QM theories.

while chatting with him, found much new info/ leads worth sharing, some from him and others while googling. a lot of my neurons have been triggered/ buzzing by a confluence of a lot of material tied to our conversation & it feels hard to pin all this down in linear words. its amazing how just having 1 other human to bounce ideas off can spark a small conflagation. do not have many to communicate in detail with on this subject. also “gazing into the crystal ball” & “reading the entrails” so to speak there seems to be some major other signs of “cybersynchronicity” ie different stuff/ threads coalescing.

this is an important/ key topic to me for over ~1½ decade now, looking at the fundamentals of QM. its always been a sort of “bordering-on-fringe” area of QM science and yet now it is seemingly recently/ finally gaining some serious scientific traction.

experienced that rare moment of intense cybersynchronicity in spotting TKs question on “toy models of QM” [k1] & found it quite worthwhile to pursue further. we started a chat room & traded many ideas/ povs in a quick meeting-of-minds.[a16] TK also asks about measuring the density matrix on the new breakaway/ spinoff site physicsoverflow, which also think is a critical part of the puzzle and going to turn into a crucial pivot (maybe in much the same way that position/ momentum atomic measurements/ theory originally led to the inception of QM).[a10]

there are many separate refs here in this post but nobody seems to be consolodating/ synthesizing all this material at the moment. taken together it is quite impressive. aka “connecting the dots/ tieing the pieces together/ looking for & at the big picture”. so excited so even went back and highlited the important stuff. breakthrough, gamechanging, paradigm shifting stuff but at the moment, few are aware of the truly staggering significance of these ideas. it all reminds me of one of my favorite quotes by a favorite author (who partly inspired my favorite movie, the matrix):

The future is already here, its just not evenly distributed. –William Gibson

Emergent QM conference 2013

there was a major conference in 2013, the Emergent Quantum Mechanics conference.[a5][a6] the declaration of this conference is quite significant/ remarkable.

The symposium was held at the ”Theatersaal” of the Academy of Sciences, and was devoted to the open exploration of emergent quantum mechanics, a possible ”deeper level theory” that interconnects three fields of knowledge: emergence, the quantum, and information. Could there appear a revised image of physical reality from recognizing new links between emergence, the quantum, and information? Could a novel synthesis pave the way towards a 21st century, ”superclassical” physics? The symposium provided a forum for discussing (i) important obstacles which need to be overcome as well as (ii) promising developments and research opportunities on the way towards emergent quantum mechanics. Contributions were invited that presented current advances in both standard as well as unconventional approaches to quantum mechanics.

the mere string of words “deeper level theory” uttered by mainstream physicists would seem to be a violation of the cophenhagen interpretation of physics, but at the 2nd half of the 2nd decade into the 21st century, it is not quite so radical. ‘t Hooft was represented. found a very key interview with him in scientific american magazine, “Does Some Deeper Level of Physics Underlie Quantum Mechanics? An Interview with Nobelist Gerard ‘t Hooft”.[a4][a12]

ah but that new breakthrough word “superclassical” is a very nice simple label/ terminology and search term for this line of inquiry and research program.

so this whole area is admittedly “going out on a limb” in some ways and TK was sensitive to that in chat, eg citing a physics.se meta policy where mainstream physics only is permitted! could not believe my eyes! 😮 but lets take some solace/ defense that this line of research has many elite investigators including a nobelist and, the modern stamp of full physics alpha-male credibility, 2 writeups by Scott Aaronson![a19][a20] (the latter for a grad student class, a very meaningful/ critical venue, which brings to mind plank’s apropos/ incisive/ timeless quote about mental rigidity vs the next generation. but still wondering, is there maybe some ulterior significance that neither is on arxiv?)

Wolchover state-of-the-QM overview/ Simons Institute

have been sitting on wolchovers very important article [a1] “Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?” since last summer (admittedly wondering if it would cause any major “ripples” but it doesnt seem to have so far; hey ok full disclosure she’s a near-popsci writer that doesnt seem to have a huge physics bkg but very experienced bkg in science writing). hyperlinked to it on my main sidebar since it appeared as a paradigm shift but havent blogged on it yet. for me it is something of a quick vindication of my earlier blog on here and my ideas on this subject going back over ~1½ decade. it cites Anderson/ Brady heavily.

To some researchers, the experiments suggest that quantum objects are as definite as droplets, and that they too are guided by pilot waves — in this case, fluid-like undulations in space and time. These arguments have injected new life into a deterministic (as opposed to probabilistic) theory of the microscopic world first proposed, and rejected, at the birth of quantum mechanics. “This is a classical system that exhibits behavior that people previously thought was exclusive to the quantum realm, and we can say why,” said John Bush, a professor of applied mathematics at the Massachusetts Institute of Technology who has led several recent bouncing-droplet experiments. “The more things we understand and can provide a physical rationale for, the more difficult it will be to defend the ‘quantum mechanics is magic’ perspective.”

more on bush in sciencedaily article, “New math and quantum mechanics: Fluid mechanics suggests alternative to quantum orthodoxy”.[b4]

another amazing cybersynchronicity, while chatting with TK, a group announced a theoretical derivation that combines wave-particle duality with the heisenberg principle. this made actual MSM headlines and ties in/ meshes very closely with the Wolchover article.[a2][a3]

Patrick Coles, Jedrzej Kaniewski, and Stephanie Wehner made the breakthrough while at the Centre for Quantum Technologies at the National University of Singapore. They found that ‘wave-particle duality’ is simply the quantum ‘uncertainty principle’ in disguise, reducing two mysteries to one. “The connection between uncertainty and wave-particle duality comes out very naturally when you consider them as questions about what information you can gain about a system. Our result highlights the power of thinking about physics from the perspective of information,” says Wehner, who is now an Associate Professor at QuTech at the Delft University of Technology in the Netherlands.

TK tipped me off to Neumaiers work which was not familiar with ( 😳 ) but is quite compelling.[a7][a8][a9][a11][a13] somewhat surprisingly he didnt have any papers at the conference. he has worked out LHV type theories wrt Bell experiments and has pushed semiclassical theory as far as it can go. [a9] is a highlight for me, its my 1st post on physicsoverflow, a response to Neumaier, and it received positive votes and thats where the Emergent QM conference turned up as cited by PV.

went and re-looked at Brady/ Anderson papers and found important stuff not yet cited on this blog that very much deserves to be.[a14][a15][b1] the rather astonishing titles (taken alone) say it all.

Violation of Bell’s inequality in fluid mechanics

Why bouncing droplets are a pretty good model of quantum mechanics

Khrennikov, acoustic undergrad experiment idea, sound digitizer LSB wave/ particle duality

➡ ⭐ 💡 ❗ while looking up physics.se posts on related areas, Borns rule came up, and TK was mentioning it in chat. that reminded me of my wondering about an old conceptual model I came up with years ago, a sound digitizer LSB and sound waves as a model for wave-particle duality. after thinking about it, now conjecture that a sound digitizer LSB might have born-rule measuring dynamics with some minor modifications. (possibly like a large “recovery/ dead time” associated with a detector.)

⭐ ⭐ ⭐ did some googling and came up with a remarkable paper by Khrennikov, emailed to ask him about it, and he tipped me off on his 2nd paper.[a18][b2] he works out all the math of classical detectors exhibiting a born-like rule wrt detecting wavefunctions, “Born’s rule from measurements of classical signals by threshold detectors which are properly calibrated”. this is a very big deal if you ask me, semirevolutionary possibly. nobody seems to be paying much attn to his ideas so far. he mentioned in email that NIST is experimentally testing some of theory. a physics.se question on the subject asking if Born’s rule has ever been observed classically has now earned me a coveted “tumbleweed badge”.

khrennikov refers to “PCST”, “Prequantum Classical Statistical Field Theory,” what is also known as roughly semiclassical theories.

TK also pointed out there is also a strong connection between these ideas and very theoretical ideas written up by Qiaochu Yuan, “Finite noncommutative probability, the Born rule, and wave function collapse” again utilizing some complex math demonstrating the Born rule can arise from the statistics of classical systems.[a21] (blog/ math.se profile)

the AB paper on Bell inequality [a14] meshes closely with some ideas that have been independently occuring to me lately. am currently pondering ideas on maybe devising a acoustic-based Bell type experiment. ofc the typical thinking would be that a bell-type experiment certainly cant be done without at least a wave medium with polarization, but am working out some conceptual details that may overcome this (substantial/ serious) difficulty. (however discovered googling there is a very old experiment by robinson 1881 Science mag that claims to measure sound polarization phenomena, & cited it on physics.se.)

years ago was very interested in Bell type experiments carried out in the undergraduate laboratory which emerged & were quite notable.[e] was hoping these would become more widespread, but it now seems like an isolated phenomenon.

the idea of studying some of this theory via lower-cost experiments is important because mainstream scientists are not likely to work in these perceived-fringe areas and making tabletop, undergraduate setups that test deep ideas could be a real “wedge” or “leverage” to “open science” type advancement in this at times extremely ambitious, slow-moving research program (it literally spans over many decades & in some ways to the very origins of QM about a century old).

so did a bit of google hunting on undergrad acoustic physics experiments & came up with a few nice results.[d] the refs seem to acknowledge that undergrad acoustic experiments are not so common but present some sophisticated frameworks. so (am very much hoping) maybe this will catch on in a way that the undergrad bell experiments unfortunately & much to my chagrin did not.

Liquid helium anomaly/ soliton measurement/ experiment candidate

was reminded of some recent news about “researchers shattering an electron wave function.”[c1][c2][c3] experiments at brown university are looking at electron trajectories in liquid helium and finding somewhat anomalous or “not explained by QM” type results.

my thinking is that these are PRIME candidates for explanation via a soliton like theory. as AB describe, a soliton “sonon” moving forward through a medium has a “leading wavefront” and it sounds a lot like the partial electron wavefunctions (there are different terms for them eg “possible electron fission”) being measured. and sure enough there is decades of writing about soliton-like phenomena in liquid helium, even recently.[c4][c5][c6][c7] simple right?

but it seems maybe also experimentalists are measuring “beyond QM” type phenomena and are not necessarily describing them like that (while there is scientific incentive to devise innovative new setups/ measurements, its also a red flag for reviewers). for example [b3] is a recent experiment that seems to assert its actually measuring the “pure” wavefunction not the modulus squared function.

physics.se superclassical-touching question survey

on chatting with TK noticed that there are many questions on physics.se that tie into superclassical questions. while its definitely a bit overwhelming (this exercise unexpectedly turned into something like the proverbial pulling a thread on a sweater, with a few dozen questions identified), this can be somewhat helpful in “reverse engineering” and creating a conceptual map of what general areas of QM would be addressed by a superclassical theory. topics like:

determinism [f]

measurement/ observation [g]

wavefn/ born rule [h]

density [i]

bell/ nonlocality [j]

(semi)classical [k]

povs on QM boundaries/ limitations/ new theories [l]

qm in biology

in the last few years theres been new research and ideas emerging in quantum mechanics in biology.[n11][n18] there is new thinking in how QM may play a role in photosynthesis, and there is some vindication of an old conjecture by Penrose about quantum effects in microtubules.[n12] overall QM in biology is a nearby leading/ exciting/ rapidly developing new research program/ paradigm/ frontier/ horizon that will be sure to be making other big headlines in the near future. some of the excitement comes from that efficient energy conversion in photosynthesis (which is presumably highly optimized by evolution over a few billion years) may have close applications in solar cell design/ optimization. another somewhat “far out” “long shot” is that studying efficient transport of “excitons” in photosynthesis may have some tie-ins to qubit transport in quantum computing (thx T Abraham for pointing this out!)[m14]

Addendums

(1/28) ⭐ 😎 🙂 lots of hits & visitors from reddit, very cool, welcome! & redditor “The_Serious_Account” has some extended reaction/ feedback while quoting aaronsons blog. two other links that may be helpful in understanding this debate. Von Neumanns impossibility/ “no-go”/ “barrier” disproof of hidden variables as cited by TK on mathoverflow (from the wolchover article), and the Wikipedia page on local hidden variables actually has some nice documentation of subtle exceptions/ loopholes found in careful analyses of Bell tests/ mathematics/ conditions/ experimental setups.

(2/4) ⭐ hanging out in & surveilling the physics stackexchange chat room & site some led me to some major cybersynchronicity and remarkable new refs. sofia posted a thorough ref to bells thm written by Shimony.[j6] much more notable a new user on physics stackexchange asked about the “reality of the wavefunction” and cited Cavalcanti in his question leading to another golden vein of closely related refs.[o] moreover the question was not shot down and now stands with a respectable +6v. more precursor signs of a paradigm shift in progress… ❓ 💡 ❗ 😮

Dr Alessandro Fedrizzi, from the UQ School of Mathematics and Physics, explains that although the quantum wavefunction is our central tool for describing physical systems in quantum mechanics, it is still unclear what it actually is. “Does it only represent our limited knowledge about the real state of a system, or is it in direct correspondence with this reality? And is there any objective reality at all?” This debate has remained purely theoretical for decades, until three teams of quantum theorists—including co-authors Dr Cyril Branciard and Dr Eric Cavalcanti—recently proposed experimental tests to answer this question. “The new approach tests whether the competing interpretations of the wavefunction can explain why we cannot tell quantum states apart with certainty, which is a central feature of quantum mechanics,” says lead author Mr Martin Ringbauer. “Our results suggest that, if there is objective reality, the wavefunction corresponds to this reality.”

(2/24) ⭐ venturing a little further into the physics.se pool after establishing some promising beachhead in the chat room. 1st, noticed some dramatic new results claimed by Murch et al that sound like at the boundaries of QM. they talk about “hard vs soft” and “steering” measurements. asked if these results are outside the boundaries of QM theory. that does seem to me to be the case. its interesting to note that QM wasnt mathematically formalized until decades after its discovery by Von Neumann, and so if anomalies are indeed observed, it can take quite awhile just to determine their exact mathematical implications wrt existing quantum formalism.

have been able to get the attention of a few physics.se regulars with a striking new paper by Bush cited in my question about the existence of computational experiments on solitons. Bush is mentioned in the Wolchover article as a strong advocate and just looked up his latest article on the subject, which is quite impressive.[a22] a chat room junkie and rep earner extraordinaire “sofia” interested in QM foundations/ interpretations said she passed it on to her colleagues and has spoken highly of it! Bush is an applied mathematican and comes more from the fluid dynamics side. another great quote from the wolchover article (which is quite chock full of them).

“I wish that the people who were developing quantum mechanics at the beginning of last century had access to these experiments,” Milewski said. “Because then the whole history of quantum mechanics might be different.”

another high rep physics.se user Terry Bollinger has spoken very highly of the Ringbauer-Cavalcanti work: “the reality of wave packets are on my mind, amazing work”.

➡ (5/26) ❗ ⭐ ⭐ ⭐ Nature covers QM soliton dynamics in review/ survey article!