[HN Gopher] Experiments spell doom for physical-collapse explana...
___________________________________________________________________
Experiments spell doom for physical-collapse explanation of quantum
weirdness
Author : pseudolus
Score : 152 points
Date : 2022-10-21 10:24 UTC (12 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| iainmerrick wrote:
| _Falsification is hard work, and rarely reaches a tidy end point.
| Even now, according to Curceanu, Roger Penrose -- who was awarded
| the 2020 Nobel Prize in Physics for his work on general
| relativity -- is working on a version of the Diosi-Penrose model
| in which there's no spontaneous radiation at all._
|
| It's incredible how influential Penrose has been for such a long
| time, and continues to be. As far as I can tell (I'm interested
| but far from an expert) very few theorists are coming up with
| genuinely testable ideas in this area.
| lamontcg wrote:
| Most scientists either blindly accept collapse as a mechanism
| and then happily use the highly accurate math and don't care it
| isn't testable, or if they think about it at all they adopt
| something untestable like MWI and then happily use the highly
| accurate math and don't care it isn't testable. Thinking hard
| about testable theories in this area is incredibly slow
| progress and doesn't pay a lot of bills
| (https://www.theguardian.com/science/2013/dec/06/peter-
| higgs-...)
| BirAdam wrote:
| I was hoping the article would be about someone experimentally
| porting Doom to a quantum computer, but... of course not.
| ccvannorman wrote:
| Not yet.
| bottlepalm wrote:
| I remember something about super determinism being a possible
| answer to this. Do these results increase the likelihood of that?
| kryptiskt wrote:
| No, none of the other explanations predicts anything like this.
| The theories that fell here predicted physical effects that
| went beyond standard quantum mechanics. The others are playing
| it safe and staying unfalsifiable.
| Nihilartikel wrote:
| I wasn't expecting them to be able to run Doom on a quantum
| computer for at least another decade!
| immmmmm wrote:
| as a former physicist and quake engine modder, your joke is
| very nice:)
|
| more seriously, having spent countless nights thinking of QM,
| it feels a bit like Nature is playing w you and your nerves.
| sillysaurusx wrote:
| Replying to a now-deleted comment:
|
| > Is there a good ... idiots guide to interpretation of quantum
| weirdness ? I am more than a little lost
|
| I've got you covered. And believe it or not, you'll be joining
| Tiktok University today:
|
| https://www.tiktok.com/t/ZTRHqk6MP/
|
| Tiktok has been quietly amassing a huge library of educational
| content, and I've been diligently sorting those into collections.
| I'll post several more related to physics.
|
| https://www.tiktok.com/t/ZTRHqLx2k/
|
| https://www.tiktok.com/t/ZTRHqBn2L/
|
| Why entangled electrons can't communicate information:
| https://www.tiktok.com/t/ZTRHqBCLq/
|
| Heisenberg uncertainty principle:
| https://www.tiktok.com/t/ZTRHq8XN3/
|
| https://www.tiktok.com/t/ZTRHqY49j/
|
| A more advanced one: https://www.tiktok.com/t/ZTRHq2pYS/
|
| And a break from quantum weirdness, just 'cause I like it:
| https://www.tiktok.com/t/ZTRHqBQHE
|
| I have pages and pages of videos, so I probably shouldn't spam
| them here. I can post more if there's any interest.
| [deleted]
| dmix wrote:
| I often post on HN that TikTok offers much more to the world
| than videos of girls dancing and silly pranks. It gives people
| what they want (for better or worse) and adapts very very
| quickly to tastes.
|
| Once it learns you're a science nerd it fills your feed with
| some high quality educational content like this. The chemistry
| stuff they have is also A+.
| macintux wrote:
| Perhaps a GitHub gist? I have a few collections that I share
| here that way.
| Comevius wrote:
| Looking out for quantum consciousness in articles about quantum
| physics would be a good drinking game, though here it is handled
| with a proper amount of scepticism.
|
| The pressure is enormous for writers to include mumbo-jumbo,
| because people click on these articles expecting to find out that
| it's possible to alter the Universe with psyhic abilities, which
| is how quantum physics is represented in social media, especially
| TikTok.
| omnicognate wrote:
| Except that in this context it isn't mumbo-jumbo at all. It's a
| falsifiable theory proposed by one of the most distinguished
| mathematical physicists in the world, in the process of being
| falsified. Perfectly respectable, though highly speculative,
| science.
|
| The article didn't include it for lulz and clicks. It's
| directly relevant.
| thrown_22 wrote:
| No one apart from Penrose took it seriously. You might as
| well say that Russell's Teapot is falsifiable because you
| only need to look through a finite amount of space to prove
| it's not there.
| yucky wrote:
| Isn't it safe to assume that everything on TikTok is make-
| believe though?
| giraffe_lady wrote:
| What is the point of this sort of joke? Just to confirm that
| we all think of ourselves as superior to anyone using tiktok?
|
| It's probably overall neither much more or less reliable than
| other social media like reddit, twitter, instagram and, sorry
| boys, HN.
| yucky wrote:
| It's not a joke. Social media is heavily curated for a
| specific agenda/angle (at best) and generally full of
| dis/misinformation. Why on earth would _anybody_ consider
| what they see on social media to be representative of
| reality?
| ThalesX wrote:
| Having been passionate about this for awhile, I have a layman's
| surface overview of the state of physics, or I like to believe
| so.
|
| It amused me to no end when my elderly aunt came to ask me for
| a tl;dr; on Quantum Physics. She stopped me shortly asking how
| she can control the universe with her mind.
|
| I tried to explain a bit about the famous interpretation
| (Copenhagen, not Von Neumann-Wigner) but she would have none of
| it because the business course she just attended had a segment
| on how to control the universe and proceeded to disregard and
| mock me.
| causi wrote:
| What I don't understand is why we call it "observation" when
| it should really be "interaction". The quantum weirdness
| resulting from the collapse of probabilities has nothing to
| do with a conscious observer, just whether and at what point
| the phenomena in question interact with something else in an
| observable way.
| abecedarius wrote:
| Well, an interaction that leaves a persistent change in
| state in the "observer".
| kgwgk wrote:
| > What I don't understand is why we call it "observation"
| when it should really be "interaction" [...] at what point
| the phenomena in question interact with something else in
| an observable way.
|
| That's why. If it's observable it could be observed by an
| observer in an observation.
| whimsicalism wrote:
| Because when an object "interacts" with another object, it
| goes into a quantum superposition with that object. It is
| only when we _observe_ that we don 't see the
| superposition.
|
| The obvious implication that people don't like to talk
| about is that there is nothing special about observation,
| it is just that our own body goes into superposition and we
| only subjectively experience one of the quantum states.
| kgwgk wrote:
| > there is nothing special about observation [...] we
| only subjectively experience one of the quantum states
|
| That subjective experience seem something special!
|
| There is nothing special about quantum superpositions -
| they are pure quantum states like any other. They are
| superpositions when we consider them in a particular
| basis. How does the subjective experience project your
| body - and the rest of the universe - onto one element of
| the right basis?
| [deleted]
| hotpotamus wrote:
| I don't really understand much of quantum physics - I'd say
| as much as someone with a passing interest in chemistry would
| need to (and that's pretty focused on what groups of
| electrons get up to), but every once in awhile I'll read
| about the actual problems and experiments that the old Nobel
| laureates got up to and all of a sudden something will fall
| into place. A big key was reading about the ultraviolet
| catastrophe and how Max Planck basically just played around
| with equations and sort of hit on quantizing energy levels
| and almost accidentally invented quantum mechanics. If my
| education had just been a history of all the discoveries in
| physics from the end 19th to mid 20th centuries (and to be
| fair to my education that was mixed in a bit), I think I
| would have been served a lot better, but I also acknowledge
| that could be down to my individual way of learning.
| wongarsu wrote:
| To be fair, the Copenhagen interpretation doesn't really fit
| today's world view. We have largely moved away from viewing
| humans or "consciousness" as something special, so the notion
| that an observer collapses the wave function just seems weird
| now.
|
| "Many worlds" or "the wave function never collapses, you are
| in a superposition" both make much more sense with how we
| currently view the world
| guerrilla wrote:
| You're thinking of the Von Neumann-Wigner interpretation,
| not Copenhagen.
| ericmay wrote:
| I'd say a good heuristic would be to include all mammals in
| any theory about consciousness, wave function collapse,
| quantum consciousness, etc. and then see if the theory
| still holds up. If it does, you are probably on to
| something.
|
| I think scientifically we will look back on "humans are
| uniquely conscious" as a categorical differentiation
| instead of a gradient with other mammals to be as absurd as
| believing the earth is the center of the universe. "Unique
| consciousness" is a quasi-religious mechanism we use at a
| societal level to not run around all the time terrified of
| death.
| danielbln wrote:
| > "Unique consciousness" is a quasi-religious mechanism
| we use at a societal level to not run around all the time
| terrified of death.
|
| It also helps us justify eating other lifeforms, mammals
| included.
| [deleted]
| Comevius wrote:
| No interpretation of quantum physics proposed by
| scientists ever required a conscious observer, that's
| more of a misinterpretation of what an observer is. It's
| an interaction, not a person or animal.
|
| As for the theory of consciousness, of course we are not
| special, it's information-processing, and it looks like
| thermodynamics is responsible for the emergence of
| information-processing structures.
|
| https://arxiv.org/abs/1203.3271
| guerrilla wrote:
| > No interpretation of quantum physics proposed by
| scientists ever required a conscious observer, that's
| more of a misinterpretation of what an observer is. It's
| an interaction, not a person or animal.
|
| Are you saying that the Von Neumann-Wigner
| interpretation[1] does not explicitly postulate
| consciousness to be necessary for the completion of the
| process of quantum measurement?
|
| 1. https://en.wikipedia.org/wiki/Von_Neumann%E2%80%93Wign
| er_int...
| Comevius wrote:
| Those guys are excused, they were early on the floor, had
| no idea what's going on. They grew up believing that
| nature is deterministic, but quantum physics complicated
| that picture a great deal.
|
| I should've said no interpretation in the 21st century.
| snowwrestler wrote:
| A mental trick that helped me understand the concept of
| "an observer" in particle physics is to imagine it like
| playing billiards in a pitch black room.
|
| In normal human-scale billiards, there are immense
| numbers of photons flying around bouncing off everything.
| The photon interactions are far too small to affect the
| path of a moving billiard ball, but we can detect them
| easily with our eyes. So we can use photons to passively
| observe the balls rolling around.
|
| But when you're trying to observe a photon itself...
| there are no tiny photon-equivalents flying around. It's
| like playing billiards in pitch black: the only way to
| know which direction a ball is rolling is to touch it.
| And you can't touch a rolling billiard ball without
| changing its path somehow. Likewise, you can't "observe"
| a single photon without interacting with it in some way.
| Comevius wrote:
| This is a great analogy, but also in experiments the
| presence or absence of the measuring device like a
| beamsplitter determines the outcome. The measuring
| device, the which-way detector is the observer, and it
| can be regarded as a quantum mechanical system. It's
| correlations with the rest of the system causes the
| particle behavior.
| JackFr wrote:
| I know all analogies are imperfect, but that is a really
| great one. It really captures the problem of observing so
| elegantly.
| Dx5IQ wrote:
| Observer effect while applicable is distinct from Quantum
| Weirdness aka Heisenberg Uncertainty
| nemo44x wrote:
| > As for the theory of consciousness, of course we are
| not special, it's information-processing, and it looks
| like thermodynamics is responsible for the emergence of
| information-processing structures.
|
| That's a really interesting paper, thanks for that. It's
| also a bit depressing to consider that there's a good
| chance that everything we think that makes us special is
| really just an emergent property of a thermodynamics
| memory and prediction system.
| Comevius wrote:
| The Copenhagen interpretation never defined an observer
| that way. It's a non-interpretation basically, just shut up
| and calculate, which is still the most widely accepted
| approach among scientists, since there are no other
| falsifiable interpretations.
| spywaregorilla wrote:
| I'm reminded of learning about the grandfather paradox as
| a kid. I recall hearing shit about scientists saying if
| you were to travel back in time, you would be compelled
| by a universal force to do things that don't alter the
| future and create a paradox. Even as a kid, that sounded
| so idiotic. In retrospect it was almost certainly the
| reporting that was wrong.
| iainmerrick wrote:
| Is that really so weird? That's a very common version of
| time travel in SF, perhaps the most common. You can
| travel back in time, and you _think_ you 're changing
| history, but through a series of unlikely coincidences
| you end up being the person who created the history you
| were trying to change.
|
| Come to think of it, maybe that's more common in short
| stories, where the "gotcha!" format works. It's probably
| harder to spin that unchangeable-history gimmick out to
| novel length, whereas "you can change history and it has
| endless weird side effects" can work well in long form. I
| can't think off-hand of any time travel novels with
| unchangeable history.
| spywaregorilla wrote:
| It's not weird. It's fun.
|
| But it's stupid as a serious time travel proposal. Things
| like "travel in back in time 5 seconds unless you see
| your future self is already there" create a hard paradox
| that this logic cannot solve. Time loops are easily
| broken by anyone interested in testing them.
| wongarsu wrote:
| Time loops are only a problem if you insist on being able
| to simulate reality by computing the next time step from
| previous ones, without discarding any. Or if you for some
| reason insist on total free will.
| spywaregorilla wrote:
| > Or if you for some reason insist on total free will.
|
| Like, the free will to do something other than what you
| saw your future self do? Yeah, you do have that. You have
| that ability even as a completely deterministic brain.
|
| Heck you could send a machine to go back in time 5
| seconds that displays a number 1 greater than the number
| it just saw its future self display from the previous
| travel and your time loop has infinitely increasing state
| with no human in the process. Or the mundane, send a bomb
| back in time to destroy the time machine and your past
| self. It's very easy to think of examples.
|
| > Time loops are only a problem if you insist on being
| able to simulate reality by computing the next time step
| from previous ones, without discarding any
|
| yes?
| iainmerrick wrote:
| You sound as confident as the protagonist of many a time
| travel short story!
|
| _Edit to add:_ your comment reminded me specifically of
| a Ted Chiang story, "What's Expected Of Us":
| https://www.nature.com/articles/436150a
|
| I found that link via a blog post that excoriates it for
| its supposed logical fallacies:
| https://loopingworld.com/2019/07/13/debunking-ted-chiang-
| rec.... I don't necessarily agree or disagree with that,
| but I _do_ disagree that it 's "obviously" logically
| wrong or inconsistent.
| spywaregorilla wrote:
| It's really just on them for trying to alter the future
| in large ways before conducting small experiments to
| understand the mechanics of the universe imo.
| HALtheWise wrote:
| If you frame the system as "the universe conspires to
| create a series of coincidences such that no paradox
| exists", then it makes perfect sense that nobody chooses
| to run that experiment, because the simplest coincidence
| that prevents the paradox is for the characters in
| question to simply _not think_ to run that particular
| experiment. This raises the obvious question of how the
| time machine got invented in the first place, which seems
| like a great story.
| spywaregorilla wrote:
| Sure sure. And it's fun fiction. But it's obviously not a
| plausible physics explanation.
| Aerroon wrote:
| > _I can 't think off-hand of any time travel novels with
| unchangeable history._
|
| Harry Potter has this as a plot point in one of the
| books. He essentially teaches/inspires himself to a spell
| to save the day.
| iainmerrick wrote:
| Ah, yeah, good one. (Although more of a "novel that
| happens to have time travel in it" than "novel about time
| travel".)
| spywaregorilla wrote:
| Netflix's Dark is a good 3 seasons of a single nearly
| stable time loop.
| tsimionescu wrote:
| The CI has absolutely nothing whatsoever to do with
| consciousness. The CI view is simply "when a quantum system
| interacts with a measurement device, the wave function of
| the quantum system changes to one of some subset of real
| values, with a probability given by the modulus of the
| amplitude of that value in the wave function". Exactly what
| constitutes a measurement apparatus is undefined, but it
| certainly doesn't involve a human.
|
| In fact, it is precisely the MWI that requires human
| observers for its explanations, at least to some extent, as
| it makes the entire notion of a classical world a fiction
| that only exists inside your own head because you are the
| one that's getting entangled with a quantum system. Any
| probability you compute in MWI is relative to you
| personally, since in MWI any possible event happens with
| probability 1 when checking at the universe level.
| telmo wrote:
| I also prefer the Many Worlds interpretation and I do think
| that it is gaining popularity in relation to Copenhagen,
| but I'm not sure what you mean by "today's world view". And
| who is this "we" that you write about?
|
| I prefer Many Worlds because it is a simpler explanation,
| so I follow Occam's razor. That's it.
|
| Consciousness and the existence of qualia remains a
| fundamental mystery. There is something definitely special
| about it, in the sense that it currently does not fit any
| scientific model. It is also a deep philosophical problem
| that started being considered millennia ago and dates at
| least all the way back to Plato vs Aristotle.
|
| In my experience, people who think that consciousness is
| somehow a settled matter simply haven't thought about it
| enough and are perhaps a bit naive on the many
| ramifications of the issue that have been explored do far.
| MockObject wrote:
| > I prefer Many Worlds because it is a simpler
| explanation, so I follow Occam's razor. That's it.
|
| Zillions of new invisible universes being created every
| moment is the simplest explanation you found?
| tsimionescu wrote:
| MWI is exactly as simple mathematically as CI, so not
| sure what you mean by "simpler".
|
| MWI still postulates the equivalent of wave function
| collapse, but instead of it happening only for the
| quantum system being measured, it is happening in the
| mind of the observer, as each "version" of that mind gets
| entangled with a single "version" of the outcome.
|
| Even if you were to accept that this process is more
| natural (so not an "assumption") than wave-function
| collapse in principle, that simplicity completely falls
| apart when you then need to recover the relationship
| between the probability of observing a certain outcome
| and the amplitude of that outcome in the wave-function.
|
| CI just says "when a quantum system described by a wave-
| function interacts with a measurement apparatus that
| measures in a certain basis, the wave-function gets
| updated to one of the values of its decomposition in that
| basis, with a probability equal to the modulus of the
| square root of its amplitude in that basis". Of course
| "measurement apparatus prepared in a certain basis" does
| a lot of work here, as we don't know how to define this
| in terms of a quantum system.
|
| To make a similar quantitative prediction, MWI needs to
| define something like "the number of worlds", so that it
| can then say something like "when a quantum system
| interacts with a measurement apparatus prepared in a
| certain basis, the measurement apparatus becomes
| entangled with the quantum system such that for each
| value of that basis state there is a number of worlds
| proportional to the square root of the amplitude of each
| value of the decomposition in which the apparatus sees
| that particular value; if we were to compute the
| probability that we happen to live in a world where the
| apparatus is showing the value X, that probability would
| naturally be higher the more worlds there are where it
| shows this value X". So, the MWI has to actually
| introduce extra elements (the worlds and their number,
| and the observer wanting to compute a probability) to
| explain the actual measured results of quantum
| experiments.
| whimsicalism wrote:
| > you then need to recover the relationship between the
| probability of observing a certain outcome and the
| amplitude of that outcome in the wave-function.
|
| I have never understood how that is a strong objection.
| We've experimentally determined that the state you are
| more likely to find yourself in is based on the squared
| amplitude. How is this different from CI but with
| probability of observing given state - which was also
| determined empirically?
|
| > Of course "measurement apparatus prepared in a certain
| basis" does a lot of work here, as we don't know how to
| define this in terms of a quantum system.
|
| Yes, this is where the Occam's razor bit comes in.
|
| > So, the MWI has to actually introduce extra elements
| (the worlds and their number, and the observer wanting to
| compute a probability) to explain the actual measured
| results of quantum experiments.
|
| The worlds and their number are equivalent to the states
| & probability of CI without having to introduce the
| "measurement apparatus" that is distinct from the quantum
| system.
| GoblinSlayer wrote:
| >MWI still postulates the equivalent of wave function
| collapse
|
| It's not postulated, but deduced from the Schrodinger
| equation. MWI is simpler in a sense that it has one fewer
| axiom. But Occam's razor isn't really applicable here,
| because it selects from otherwise equal theories, which
| CI isn't. There are more important criteria to use before
| Occam's razor.
| didericis wrote:
| Exactly. A related deep millennia old observation is that
| no one has actually seen the real world. Everything we've
| ever experienced has been filtered through our minds.
| Every experiment, every measuring device, every
| meticulously crafted model of reality... it is all
| inescapably limited by what we are able to experience.
|
| One could and many have argued that the reality we've
| been observing and operating in _is_ consciousness. The
| "real" world could be entirely different and largely
| inaccessible.
|
| These kinds of thought exercises don't have much
| practical utility, apart from one very important feature;
| they humble you. At the end of the day we don't
| fundamentally _know_ anything, and should always
| recognize that at its most basic root level, everything
| we do is an educated guess. A fundamentally skeptical and
| curious outlook that acknowledges our perceptual
| limitations is how we got all of the sophisticated models
| of very difficult to observe phenomenon in the first
| place. If we want to continue to get the best
| understanding of whatever it is we're experiencing, I
| think it's very important to stay humble and ensure our
| knowledge is treated as a hard earned set of well
| reasoned guesses rather than unquestionable dogma. 99.9%
| of objections to well established ideas and models might
| be a waste of time entertaining, but you never know what
| might turn out to be the seeds of a whole new universe of
| understanding that invalidates huge swaths of our
| existing corpus of knowledge.
|
| Most of what I'm saying here is probably obvious to a lot
| of readers, and I don't think anyone in this thread is
| being particularly arrogant or dogmatic, but I think it's
| worth reiterating. If people who understand the limits of
| knowledge aren't constantly emphasizing the fact that we
| don't know what we don't know, that creates fertile
| ground for both dogmatic assertions and unreasonable
| skepticism, and I think a huge amount of dysfunction in
| the culture at large is explained by insufficient well
| calibrated humility amongst otherwise very intelligent
| people who set an example for others.
| ben_w wrote:
| What surprises me is not that many people think
| consciousness is a settled matter; but rather, people
| who, when faced with the claim that "consciousness" isn't
| settled, are so often tempted to assert that it _is_ that
| they rapidly provide another example of how it _isn 't_.
| dizzant wrote:
| > We have largely moved away from viewing humans or
| "consciousness" as something special.
|
| Who is "we" in this comment? Christianity and Islam
| emphasize consciousness and the uniqueness of human
| experience, and their adherents still account more than 50%
| of the population.
|
| As much popularity as the many worlds theory is gaining,
| the generic "we" almost certainly still doesn't believe it,
| and many (most?) probably don't even know about it.
| masteranza wrote:
| This article is a perfect example how science is getting led into
| dark areas by people who didn't learn quantum mechanics right or
| people who pretend to understand it, but can only blindly follow
| the formalism without much understanding of what they actually
| do. Every such article continuous to mysticize the whole subject
| by quoting famous scientists who were either puzzled by it at the
| time or scientists like John von Neumann who clearly gave a
| dumbed down view of the now called collapse (perhaps on request
| to skip the math).
|
| I really appreciate this forum - as it is one of the last places
| that I know of where one can have a civil discussion - and
| therefore I will take the effort to show that pure quantum
| mechanics - with no additions - essentially explains the process
| of measurement which is not at all sudden as the name "collapse"
| would suggest. The reasoning comes from von Neumann himself, but
| now sometimes it's attributed also to Wojciech Zurek.
|
| TLDR of below: All processes in nature, including the measuring
| process are unitary, the "collapse" is just an artifact of our
| ignorance about the exact state of the measuring aparatus. Here
| it goes:
|
| For simplicity, let's assume that psi describing our particle is
| a superposition of two eigenstates: |psi> = c1 |1> + c2 |2>,
| i.e., |c1|^2 + |c2|^2 = 1. Without loss of generality we can
| pick: c1 = x and c2 = sqrt(1-x^2) exp(i phi), where x is a real
| number smaller than 1. The density matrix of this pure state can
| then be written as rho = |psi><psi| and one by writing the
| explicit form of this density matrix one can see that the
| diagonal terms are: x^2 and 1-x^2, while the non-diagonal terms
| are: x _sqrt(1-x^2) exp(i phi) and x_ sqrt(1-x^2) exp(-i phi).
|
| In the most complete scenario of a measurement, the density
| matrix of the system can change change in many ways including the
| diagonal terms of the density matrix. However in this simplistic
| example, a measurement will by necessity, bring only the non-
| diagonal terms to zero (I hope most of the interested readers
| will have enough background to understand why).
|
| Now, the measuring device, as a macroscopic object, will have the
| number of degrees of freedom far greater than the simple particle
| which's state we're about to measure. This number will be the
| order of the Avogadro number (~ 10^23) - even the smallest human
| visible indicator will be this big. The measurement, by
| necessity, includes an interaction of our small system with the
| enormous measuring device.
|
| Before the interaction the whole system (the particle and the
| measuring device) can be written as a tensor product of the two
| wavefunctions:
|
| |Omega_before> = |Psi> [?] |Xsi> = ( c1 |1> + c2 |2> ) [?] |Xsi>
|
| where |Xsi> represents the wavefunction of the measuring device
| and everything it interacts with before the measurement. When the
| interaction occurs the state of our measuring device changes
| unitarily (as everything in nature) according to the full
| Hamiltonian of the system, and with some regrouping of the terms,
| we can write the state after the interaction as:
|
| |Omega_after> = c1 |1> [?] |Xsi_1> + c2 |2> [?] |Xsi_2>
|
| This is the true state of the system as performed by nature. The
| individual subsystems are no longer in pure states, but the whole
| system |Omega_after> (if we're able to completely describe it) -
| is.
|
| Now, comes the final part, which some call the "collapse", but in
| reality it is just "an average" over all possible states of the
| bigger (measurement) system *which we declared apriori to not be
| the system of interest and states of which not able to follow
| because we measure with it*:
|
| Tr_{over the degrees of freedom of Xsi}
| |Omega_after><Omega_after|
|
| In result we obtain a matrix after the measurement which is just
| formed with the diagonal elements x^2 and 1-x^2, i.e., the
| probabilities of the two measurement results and non-diagonal
| terms being equal to zero.
|
| Why are they zero? Let's inspect one of the non-diagonal elements
| over which the above trace is taken: x*sqrt(1-x^2)exp(i phi)
| <Xsi_1|Xsi_2>
|
| It is effectively zero, because the trace over the degrees of
| freedom of Xsi is a mutliple integral, again of the multiplicity
| of order of Avogardo number and a similar number functions which
| change in various ways. It is enough that only a fraction of such
| integrals will have a value lesser than 1 to guarantee that the
| product will be equal to zero.
|
| And this is all. Any attempt to change this fact would need to
| reject quantum mechanics completely, because probability calculus
| is at the heart of it.
| thrown_22 wrote:
| This is just _one_ interpretation of wave function collapse and
| the only thing it has going for it is that the dimensionality
| in which collapse happens can always require another particle,
| which adds another complex degree of freedom, and always
| remains out of the realm of what we can compute.
|
| Two particle interactions show nothing like wave function
| collapse, neither to three of four. Until you say a reasonable
| number of particles that make up the measuring apparatus where
| we should see _something_ weird starting to happen
| theoretically you're not even wrong.
| masteranza wrote:
| Nothing "weird" starts happening. Unitarity evolution is
| never broken, there are just rules in quantum mechanics that
| could perhaps be grouped under supplementary framework
| related to how we, macroscopic entities, extract information
| from it.
| dzdt wrote:
| There is an often-repeated statement that different quantum
| mechanical theories are equivalent. This is an over-
| simplification. Is wave function collapse is a real thing or just
| an approximation of what happens when a large system is
| entangled?
|
| Some smart people have tried to make theories where wave function
| collapse is a real thing. These new experiments are working to
| rule out those ideas.
|
| My feeling is that Everett's "many worlds" interpretation is the
| clear favorite: there is no wave function collapse.
| zhouyisu wrote:
| A interesting deduction:
|
| By making quantum computer, we are making us into Schrodinger's
| Cat. Which entangles our destiny to a quantum possibility.
|
| Such as a highly sophiscated military quantum computer which
| decides war and peace on quantum computing.
|
| It must be very fun to observe us from a Alien Species's angle.
| spywaregorilla wrote:
| Quantum computing is a means to avoid checking wrong
| solutions en route to solving certain types of problems.
| Seems very unlikely for this kind of decision to ever depend
| on a quantum computer.
| pred_ wrote:
| > Is wave function collapse is a real thing or just an
| approximation of what happens when a large system is entangled?
|
| I've listened to enough Carroll to convince myself that I think
| MWI makes sense, but what I never got is that it doesn't seem
| to offer much in terms of explanation of how the entangled
| state ends up being what it is: We see a particular result of
| an experiment with many possible a priori outcomes, but is
| there a mechanism that determines which particular entangled
| state we end up in? Something like the phases of the wave
| functions on individual Hilbert space sectors conspiring to
| produce a certain outcome, so that an omnipotent observer with
| full access to both parts would be able to tell what happens a
| priori, no dice being rolled? Or is that just hidden variable
| theory?
| krohling wrote:
| > it doesn't seem to offer much in terms of explanation of
| how the entangled state ends up being what it is:
|
| According to MWI, all possible results of an experiment are
| manifest and real. You're asking "which particular entangled
| state we end up in?". You end up in all of them. For a
| 2-state superposition system, there are 2 versions of "you"
| that exist after the experiment, both of which are equally
| real. Subsequent measurements of the quantum system will
| appear to be "collapsed" for both versions of you but each
| will see different and opposing values.
| lamontcg wrote:
| > You end up in all of them.
|
| Except that I've only ever experienced ending up in one of
| them, so exactly how did the "I" that is typing this right
| now wind up here, and not in some other branch?
|
| There's an unexplained bifurcation of consciousness implied
| by MWI which it cannot explain (although I think it
| suggests the appeal of MWI since it gives enough wiggle
| room that people think that their free will could control
| which universe they wind up in, which appeals to everyone's
| inner Malcolm Gladwell).
| GoblinSlayer wrote:
| You end up in all branches and your consciousness ends up
| in all branches, where your mind works. MWI works best
| with physicalism, yep :)
|
| Maybe your copy in another branch even posted the same
| comment.
| lamontcg wrote:
| But how does bifurcation of consciousness happen and how
| does it diagonalize the state so that we never see a cat
| in a complex linear superposition of |alive> and |dead>
| at the same time? 1/sqrt(2) |alive> + 1/sqrt(2) |dead>
| should be an equally valid outcome of the experiment via
| purely unitary evolution.
| Filligree wrote:
| That's just hidden variable theory. The answer for MWI is
| "all of them".
| bnralt wrote:
| > There is an often-repeated statement that different quantum
| mechanical theories are equivalent.
|
| Worse than that, I'd say that "physical collapse" is usually
| presented to the general public as established scientific fact,
| even by prominent scientists that know better.
| jfengel wrote:
| That's right: the "collapse" interpretation is an
| approximation.
|
| You can derive if from the MWI. We already know that the
| "worlds" separate and almost completely cease interacting. The
| interactions decrease to the order of "two to the power of
| Avogadro's number" almost immediately. The collapse
| interpretation rounds that to zero (at some arbitrary point).
|
| To make that more concrete you have to add a term to the
| equations, making it theoretically testable, but it's
| remarkable that anybody could manage to test it in practice.
| It's clever to use a neutrino detector -- something designed to
| measure ludicrously small amounts of interactions.
|
| I don't think anybody is surprised by the results, just that
| they could get any. The un-physical arbitrariness of the cutoff
| caused problems from the get-go.
|
| I was going to say that it doesn't make MWI any more palatable,
| though I suppose it does. They've detected the other branches,
| albeit in a very indirect way. They're real. But they're just
| as inaccessible as they ever were.
|
| You still need the concept of decoherence to make it work. The
| unstable equilibrium can't hold for large objects. That's both
| mathematically and physically sound.
| mjan22640 wrote:
| Could the other branches be our dark matter?
| jfengel wrote:
| No. They don't behave at all like dark matter. Among other
| things, there's no reason for them to be distributed in a
| halo, nor for some galaxies to lack them.
| plutonorm wrote:
| Broad statements, do you have the time to elaborate?
| gus_massa wrote:
| The Milky Way and other similar galaxies look like spiral
| drawn in a thick 2D disk.
|
| The dark matter halo looks like an invisible 3D ball
| around the thick 2D disk.
|
| Something like
| https://www.google.com/search?q=dark+matter+halo&tbm=isch
| simonh wrote:
| Dark matter affects some galaxies, but the rotation of
| others is completely explained by the observable matter.
| Why would one galaxy be influenced by its many worlds
| twins, but not another?
| jameshart wrote:
| Sci-fi plot concept answer: because one galaxy is
| populated by sentient life, and the other isn't.
| tremon wrote:
| Quarantine by Greg Egan explores this concept (the many-
| worlds theory, without the dark matter).
| pdonis wrote:
| _> You can derive if from the MWI._
|
| Not as an actual physical process, no. "Collapse" in the MWI
| just means that, once the "worlds" have decohered, within
| each "world" the wave function can be collapsed to the one
| that describes the measurement result observed in that
| "world", for purposes of predicting future results. But in
| the MWI this is just a mathematical convenience and doesn't
| correspond to anything physically happening.
|
| In the theories being tested by the experiments described in
| this article, though, collapse is an actual physical process:
| there is only one "world". This contradicts the MWI.
|
| _> They 've detected the other branches, albeit in a very
| indirect way._
|
| What experiments are you referring to here?
| whimsicalism wrote:
| > doesn't correspond to anything physically happening
|
| It corresponds to the inner product of the two branches of
| the wavefunction going to 0 due to physical phenomenon.
| pdonis wrote:
| That is decoherence, not collapse. Collapse, as a
| physical process, would be all of the branches but one
| ceasing to exist.
| whimsicalism wrote:
| Oh I misread your comment - I thought you were referring
| to decoherence as the mathematical convenience. Now that
| I see that it was collapse, definitely agree.
| dchichkov wrote:
| If quantum computers would work, it would be very difficult
| to explain "where" the computation happens without having
| some sort of MWI into picture. But if, somehow, quantum
| computers keep their noise levels up without producing any
| interesting acceleration I'll expect that a theory would
| emerge at some point explaining that. And it may disambiguate
| which interpretation is the one.
| tsimionescu wrote:
| Quantum computers are easy to explain in CI as well: they
| simply exploit certain numerical properties of complex-
| valued probabilities (unlike the real-valued probabilities
| of classical probabilistic Turing machines).
| andrewgleave wrote:
| The Logic of Experimental Tests, Particularly of Everettian
| Quantum Theory:
|
| https://arxiv.org/pdf/1508.02048.pdf
| TheOtherHobbes wrote:
| I don't see how relabelling "collapse" to "separation" and
| adding more or less infinitely proliferating universes solves
| the problem.
|
| MWI also contradicts itself. Supposedly the universes are
| independent, but if their influence doesn't define the wave
| equation they do nothing to help explain it.
|
| It's a very strong and exceptional claim with absolutely no
| evidence to support it. "Feeling" isn't enough.
| Lichtso wrote:
| > I don't see how relabelling "collapse" to "separation" and
| adding more or less infinitely proliferating universes solves
| the problem.
|
| MWI isn't just renaming the collapse. Copenhagen is
| fundamentally different in that exactly one outcome is
| somehow chosen / selected and all others cease to exist. In
| other words Copenhagen has to add / invent some information:
| Which world to pick and when to do so. MWI simply avoids
| having to pick by continuing every branch simultaneously and
| recursively.
|
| Meaning that MWI is actually a simpler theory and shows that
| the selection is unnecessary and all problems that come with
| it can be avoided. In that sense, the burden of proof lies
| with Copenhagen IMO and it just gives handwavy answers that
| the selection process somehow involves a conscious observer,
| whatever that is ...
|
| > MWI also contradicts itself. Supposedly the universes are
| independent, but if their influence doesn't define the wave
| equation they do nothing to help explain it.
|
| In MWI the wave function IS the integral of all possible
| outcomes / worlds / branches. In that sense they don't just
| influence it, they define it. Not sure how that is
| contradictory.
|
| Btw, the same goes for Copenhagen in the state of super
| position as well. So, they are identical up to the point
| where Copenhagen selects one (collapses) and MWI simply
| carries on.
| kgwgk wrote:
| > Copenhagen is fundamentally different in that exactly one
| outcome is somehow chosen / selected and all others cease
| to exist.
|
| In MWI exactly one outcome / branch is somehow what we see
| and all others cease to exist to us. MWI just gives
| handwavy answers about how it is so.
| Lichtso wrote:
| It follows by contradiction of the opposite statement:
| Lets say that all "you"s across all branches perceive all
| the other branches as well. That means that they do
| influence each other. In other words they are not
| separated and never where different outcomes to begin
| with.
|
| But, all the interpretations of quantum mechanics start
| with the axiomatic assumption that the universe is modal
| and that there are different possibilities / outcomes.
| They only differ in if they chose to turn hypothetical
| outcomes into real outcomes or simply let everything be
| equally real from the get-go.
|
| And yes, even superdeterminism has to deal with / model
| hypothetical outcomes. It just says that some of them
| cancel out each other early on as they would lead to
| inconsistencies in the future otherwise.
| krohling wrote:
| I don't believe "feeling" has anything to do with the MWI
| interpretation. At least I've never heard it described that
| way.
|
| Given the equations that describe quantum mechanics (ie
| Schrodinger equation) MWI is essentially the "null
| hypothesis". No equations that describe collapse have ever
| passed the rigor of experiment and all collapse theories
| require modifications to the mathematics of QM. The burden of
| proof here is on theorists that support collapse theories not
| proponents of MWI.
| kgwgk wrote:
| > MWI is essentially the "null hypothesis"
|
| Null hypothesis in the sense of not producing any
| predicition? /joking
|
| I agree with the grand-parent that substituting a
| "collapse" that we cannot understand with a "separation"
| that we cannot understand doesn't seem a big step forward.
| c1ccccc1 wrote:
| It's not just a relabelling. In collapse theories, the
| wavefunction stops obeying the Schrodinger equation for a
| moment and discontinuously jumps to a new state. The times
| when it performs a discontinuous jump are called
| "measurements", though this doesn't necessarily mean there's
| a scientist sitting there with a ruler, it just means that
| the system has interacted with its environment sufficiently.
| In the many worlds theory on the other hand, the wavefunction
| continues to obey the Schrodinger equation for all time, and
| the natural result of this is that the wavefunction becomes
| very complicated and entangled, so that the motion of atoms
| here on Earth is very entangled with photons heading away
| from us at the speed of light out into deep space, along with
| pretty much everything else. But there's no mention of
| "separation" or "worlds" in the basic description of the
| theory; the one sentence description of many worlds is "the
| wavefunction obeys the Schrodinger equation all the time with
| no exceptions".
|
| Where the worlds come in is that it's impossible to do
| calculations on the wavefunction of the entire universe, so
| we need to come up with a way of dividing it up into
| manageable pieces. Not because the theory requires that it be
| divided into pieces, but because otherwise we couldn't handle
| the math. The worlds are one of the ways we do that: We break
| the wavefunction of the universe into approximately
| perpendicular components that don't interfere with each other
| very much and don't have too much entanglement making them
| hard to understand, and we call those worlds. We can further
| simplify things by just looking at a subsystem of the
| universe rather than the entire universe, which involves
| taking a partial trace (this tends to introduce randomness).
| As time goes on and entropy increases, the entanglement and
| complexity even within a "world" will continue to increase
| and at a certain point we may notice, "hey, this component is
| really complicated now, and it can itself be divided into
| subcomponents that are approximately orthogonal and don't
| really interact with each other much, I can simplify my
| calculations by treating those as separate worlds now". This
| is what we mean when we say that worlds tend to split apart,
| but since the worlds are only approximately orthogonal and
| independent, when you define splitting is really a matter of
| how much error you're willing to allow in your calculations.
| (Also, the process of splitting is driven by increasing
| entropy, so when (if?) the universe reaches a point of total
| heat death and entropy stops increasing, this will also imply
| that the worlds have stopped splitting.)
|
| So I'm not sure what you mean by "strong and exceptional".
| It's just math, and can be compared with experiment just like
| any other piece of physics. Take the experiments done in the
| original article. If any kind of collapse had been observed,
| then that would have straight-up falsified the many worlds
| theory. Many worlds says that physical systems can become
| entangled with their environments, but their wavefunctions
| can never just collapse, and these two cases are
| distinguishable in a careful experiment. Since collapse
| wasn't observed when these tests were done, that provides a
| little bit of evidence in favour of many worlds.
|
| Falsifiability is a little more complicated for collapse
| theories. People don't agree on the exact definition of a
| "measurement", and what level of interaction with the
| environment is required to trigger a collapse, but in order
| to have a falsifiable theory, it's important that we have a
| precise, mathematical definition of when a collapse should
| happen (this definition does not have to be deterministic, it
| could just give us a probability distribution). So various
| people have put forward different definitions, and it sounds
| like these experiments have ruled out a bunch of them, but
| obviously they haven't ruled out every collapse theory put
| forwards by every physicist ever. It's a bit like when the
| LCH failed to find any supersymmetry particles, and some
| physicists were like, "okay, but in my version of
| supersymmetry, the particles are heavier than the energies
| reachable by the LHC so of course we wouldn't expect to have
| seen them".
| criddell wrote:
| > My feeling is that Everett's "many worlds" interpretation is
| the clear favorite
|
| But what are the worlds?
|
| My feeling is that Max Tegmark has it right. Everything is
| mathematics.
| im3w1l wrote:
| We can detect their presence because they cause interference
| with our own.
| naasking wrote:
| Circular. You have to already accept many worlds to take
| this as evidence of worlds. You can argue for Many-Worlds
| on grounds of parsimony and clarity, but that's it.
| im3w1l wrote:
| No I don't think so. Many worlds is basically the
| hypothesis that we can put arbitrarily large systems in
| superposition. Like schroedingers cat that is both dead
| and alive, but instead it could be the whole lab, the
| whole planet, the whole galaxy that is simultaneously in
| two different states. We could test this by trying to
| actually do it, by putting really large and complex
| systems in superposition. If they both evolve as we'd
| predict and cause the interference patterns we predict,
| then we must conclude that these "other-labs", "other-
| planets", "other-galaxies", "other-worlds" evolve just
| like ours, and have a causal effect on ours.
|
| Saying that sure, they evolve like ours, and sure they
| affect ours, but even so they are not real - that is I
| suppose one stance, but then you are getting pretty close
| to solipsism.
| criddell wrote:
| > We could test this by trying to actually do it, by
| putting really large and complex systems in
| superposition.
|
| Is there any hope that one could actually do this? The
| article mentions that large systems may be self-observing
| (via gravity).
| GoblinSlayer wrote:
| I thought there's a quasi-classical approximation of
| quantum gravity, it doesn't work only for event horizon
| due to infinities there, but should work fine for diffuse
| matter, like how most calculations for electron orbitals
| use classical electromagnetic field.
| naasking wrote:
| > Saying that sure, they evolve like ours, and sure they
| effect ours, but even so they are not real - that is I
| suppose one stance, but then you are getting pretty close
| to solipsism.
|
| No, you'd get something like Bohmian mechanics, or
| Rovelli's relational interpretation. Which is my point:
| you can only take this as evidence of other worlds if you
| basically smuggle those assumptions in.
| spywaregorilla wrote:
| Mildly different wobbled electrons.
| criddell wrote:
| And what are the electrons? AFAIK, they are excitations
| within a quantum field. And what's a quantum field? Each
| layer down seems to get closer and closer to pure
| mathematics.
|
| I wish I understood it better.
| d_tr wrote:
| > I wish I understood it better.
|
| Me too but... It would still be some form of mathematics
| as soon as you tried to write it down in a neat, precise
| way for others to understand it. Maybe exotic math, but
| still math :p
| plutonorm wrote:
| Just go full Idealism. All things that can be - just are. A
| block universe, of all possible things and all possible
| interrelation of things. A giant timeless crystal of qualia.
| It's pretty obvious to me now.
|
| One location in the latent space of a latent diffusion model
| is a view into a universe that is as real as ours. That half
| cat, half dog monstrosity you accidentally created. It exists
| as a drawing, or as a physical mass of flesh, with every
| possible back story as to how it got there. And also every
| possible future.
|
| edit- brain fart
| herdcall wrote:
| Check out "superdeterminism," first proposed by Bell (of Bell's
| inequality fame) himself and currently being vigorously pursued
| by Sabina Hossenfelder. There is no "collapse" per se according
| to this model and everything is really classical with hidden
| variables, and the entanglement comes because everything shared
| the same origin (the big bang). A very fascinating and in my
| opinion the best explanation, though it's extremely
| controversial and taboo because of its implications on free
| will (e.g., I see no mention of it at all in this article).
| iainmerrick wrote:
| I have never fully understood that idea, even after reading
| Hossenfelder's posts about it. The idea that there's a "block
| universe" and everything is predetermined is comprehensible,
| sure; but what's the exact mechanism by which Bell's
| inequality is violated in experiments? Doesn't that require
| the universe to have been carefully set up to look as if it's
| acting in a weird non-local way, on an experiment-by-
| experiment basis? I assume I am just misunderstanding the
| idea, though. Any suggested reading material much
| appreciated!
| superposeur wrote:
| Agreed -- superdeterminism is not so much a theory as a
| theory-for-a-theory at this stage (a vague guess at the
| form such a theory might take).
|
| It is a sign of the much greater maturity of the physical
| collapse models that their parameters can be constrained by
| experiment. The ability to be constrained is a _good_ sign,
| not a bad one.
|
| I love John Preskill's standard nod to superdeterminism in
| his writings: without mentioning it by name he says "I
| leave it up to the reader to decide how seriously to take
| this possibility" (get it?)
| naasking wrote:
| I think the right way to look at it is that
| superdeterminism is an umbrella term for a _class_ of
| theories that have a certain property. Like some
| interpretations of quantum mechanics are "psi-ontic",
| meaning the wave function is considered physically real
| (like many worlds), vs. "psi-epistemic" where the wave
| function is considered a reflection of our knowledge of
| reality (Copenhagen).
| naasking wrote:
| We had a recent thread about an article from Tim Palmer who
| has a good take on this:
|
| https://news.ycombinator.com/item?id=33223391
|
| The idea is that the natural laws are fractal, which when
| mapped out trace many state space configurations. But with
| a fractal there are always gaps in state space that remain
| no matter how much you zoom in or out; fractals preserve
| certain structural invariants at all scales.
|
| So the idea is that counterfactual reasoning sometimes
| fails in a fractal universe, because statistical
| independence no longer works as a general rule (your
| counterfactual could lie in one of those gaps). He first
| published this idea in 2009 under the name "invariant set
| postulate":
|
| https://en.wikipedia.org/wiki/Invariant_set_postulate
|
| His paper with Hossenfelder is also a good overview:
|
| https://www.frontiersin.org/articles/10.3389/fphy.2020.0013
| 9...
|
| Superdeterminism gets an unnecessarily bad rap.
| iainmerrick wrote:
| _Superdeterminism gets an unnecessarily bad rap._
|
| If determinism is true, don't you mean "necessarily"? :)
| pdonis wrote:
| _> Doesn 't that require the universe to have been
| carefully set up to look as if it's acting in a weird non-
| local way, on an experiment-by-experiment basis?_
|
| Yes. That is a big reason why most physicists do not favor
| superdeterminism.
| geertj wrote:
| I am not so sure. In my understanding of the block
| universe, causality doesn't really exist, and the
| universe is simply a consistent solution with boundary
| conditions both at the beginning and at the end of time
| (as well as in space).
|
| The game of life is perhaps a nice analogy here. On the
| 2d grid of the game of life, a glider seems moving in a
| certain direction when time moves forward. But in the 3d
| grid, where time is the third dimension, a glider is just
| a static volume of space.
|
| The reason we experience time is that the evolution of
| the block universe does depend on the dimension you look
| at (e.g entropy generally increases in the positive time
| dimension), and because our consciousness is an emergent
| property of a self-sustaining structure within the block
| universe, it's plausible at least that we perceive
| movement in time different from movement in space. I
| realize this is very sloppy wording but I'm having
| trouble finding better words to describe my intuition
| here.
| pdonis wrote:
| _> In my understanding of the block universe, causality
| doesn 't really exist_
|
| That's one way of interpreting it, but superdeterminism
| does not entail or require this. Superdeterminism can be
| formulated just fine for a universe that evolves in time
| from some initial state according to causal processes.
| kgwgk wrote:
| > what's the exact mechanism by which Bell's inequality is
| violated in experiments?
|
| It's not violated - it simply doesn't apply because it's
| predetermined that the measurements that are done work well
| together. The experimenters follow the script.
| inwit wrote:
| That a serious scientist can believe this leads me to
| consider the economic benefits of believing such
| nonsense, rather than prompting me to examine it further.
| Just total rubbish
| kgwgk wrote:
| We should be merciful with superdeterminists: they don't
| have a choice!
| AnIdiotOnTheNet wrote:
| Even without superdeterminism free will is a concept that
| only makes any sense in specific contexts. To say otherwise
| is to introduce God of the Gaps style woo.
| ffhhj wrote:
| Free will is about choosing what binds us, as we can't
| choose being free of matter without becoming inmaterial.
| EamonnMR wrote:
| The notion that a probabilistic world enables free will in a
| way that a deterministic one doesn't still confuses me. A
| coin I flip isn't exercising free will.
| dilap wrote:
| Could free will be explained as super-physical phenomena
| that "haunts" the physical world, w/ choice manifest as
| which of the branching many worlds' paths consciousness
| "chooses" to experience?
|
| E.g., I am in some universe taking every possible action
| right now, but I'm only _experiencing_ the actions which I
| "chose" to take.
| kgwgk wrote:
| > Check out "superdeterminism," first proposed by Bell (of
| Bell's inequality fame) himself
|
| "Proposed" - but as something that avoids the issue but it's
| not worthy of much consideration. - I was
| going to ask whether it is still possible to maintain, in the
| light of experimental experience, the idea of a deterministic
| universe? You know, one of the ways of
| understanding this business is to say that the world is
| super-deterministic. That not only is inanimate nature
| deterministic, but we, the experimenters who imagine we can
| choose to do one experiment rather than another, are also
| determined. If so, the difficulty which this experimental
| result creates disappears. - Free will is an
| illusion - that gets us out of the crisis, does it?
| That's correct. In the analysis it is assumed that free will
| is genuine, and as a result of that one finds that the
| intervention of the experimenter at one point has to have
| consequences at a remote point, in a way that influences
| restricted by the finite velocity of light would not permit.
| If the experimenter is not free to make this intervention, if
| that also is determined in advance, the difficulty
| disappears.
| sebastialonso wrote:
| Is superdeterminism even falsifiable?
| naasking wrote:
| Is Many-Worlds even falsifiable?
| GoblinSlayer wrote:
| Discovery of non-linearity in the evolution operator
| would falsify MWI. Like e.g. this germanium experiment
| gave a positive result.
| naasking wrote:
| Yes, because it falsifies every interpretation of quantum
| mechanics not just MWI itself. I think in context here,
| "is superdeterminism falsifiable" is as silly a question
| as "is logic falsifiable" or "is causality falsifiable".
| Specific mmathematical, causal or superdeterministic
| models are always falsifiable, but the idea that
| superdeterminism as a whole is not falsifiable should be
| no more surprising or interesting than the fact that
| logic is not falsifiable.
| GoblinSlayer wrote:
| If superdeterminism allows specific models. The idea is
| that the experimenter's behavior is fine tuned so he
| can't discover superdeterminism, which means
| falsification would be a paradox by definition.
| naasking wrote:
| Given we can enumerate all possible models because we can
| enumerate all possible Turing machines, we clearly have
| enough degrees of "freedom" in this universe that that
| isn't an issue.
| tshaddox wrote:
| David Deutsch seems to think that a general intelligence
| running on a quantum computer ought to be able to observe
| itself existing in parallel worlds if many-worlds is
| true.
| naasking wrote:
| I'm skeptical that Deutsch actually meant that, but even
| smart people have crazy ideas.
| tshaddox wrote:
| He wrote a pretty well known article about it that as far
| as I can tell wasn't written off-hand and hasn't been
| retracted or disavowed. I'm pretty confident he meant it.
| ffhhj wrote:
| > observe itself existing in parallel worlds if many-
| worlds is true
|
| If many-worlds is true, we are already observing
| ourselves in each of those universes in which we can
| observe, we just don't communicate with our replicas. And
| if the AGI can communicate with its other instances, the
| exponential replicas will quickly overload their channel.
| tshaddox wrote:
| I think the point of the claim is that a general
| intelligence running on a quantum computer would make
| _different_ observations if many worlds is true versus if
| many worlds is false.
| xwolfi wrote:
| Which sadly means nothing, so many details being hidden
| behind the words "general", "intelligence", "running",
| "quantum computer", "ought", "oberve" and "existing".
|
| If you could refine what these words all mean, I guess we
| could understand it as something more than "Deutsch seems
| to think that yes", which can replace your sentence
| entirely, "yes" describing it all as precisely.
|
| I am myself, in some ways, a general intelligence running
| on a quantum computer but I dont feel like I can observe
| myself existing in a novel special way. Let alone being
| able to then express it for you in a way that is novel as
| well.
| tshaddox wrote:
| Most of those words don't cause definitional problems
| here any more than they do for all other scientific tests
| which involve general intelligences (humans) making
| observations about things that exist. "Quantum computer"
| is a unique term that doesn't show up in every
| description of a scientific experiment, but as far as I
| know it doesn't have a particularly ambiguous definition.
|
| And while you are indeed a general intelligence, I don't
| think you're running on a quantum computer.
| kanzenryu2 wrote:
| Hopefully this is on point https://www.lesswrong.com/post
| s/DFxoaWGEh9ndwtZhk/decoherenc...
| whimsicalism wrote:
| > though it's extremely controversial and taboo because of
| its implications on free will
|
| Uhh, no. Essentially all existing physical theories are
| devastating for any non-compatabilist account of free will.
| tsimionescu wrote:
| > it's extremely controversial and taboo because of its
| implications on free will (e.g., I see no mention of it at
| all in this article).
|
| "True" free will is ruled out by all existing physical
| theories, so that's not why it's controversial. The bigger
| problem with superdeterminism is that it wants to explain
| physics without assuming statistical independence, even for
| far away events.
| drewrv wrote:
| I'm a fan of hers but I think many of her criticisms of
| string theory, multiverse stuff, etc, apply equally well to
| superdeterminisim.
|
| That being said, in her latest book she has a pretty strong
| argument against free will that does not require
| superdeterminisim so if that sounds interesting check it out.
| rubidium wrote:
| Many worlds is just some peoples favorite because they get too
| weirded out but indeterminism. They prefer a billiard ball
| universe and so invented the hairbrained many worlds theory.
| ravi-delia wrote:
| Or- and hear me out with this one- they prefer an explanation
| which follows naturally from existing experiments and doesn't
| require a hacked together non-linear irreversible operation
| which occurs only under bizarre conditions exactly when
| needed to patch over experimental results. No one in the
| whole world cares if the universe is deterministic or not,
| but collapse is embedded in an _entirely_ deterministic
| system. MWI may not be right, but collapse is wrong.
| shadowfox wrote:
| > MWI may not be right, but collapse is wrong.
|
| Such confidence ... I envy that.
| nil-sec wrote:
| It's quite nice to have something irreversible though. It
| gives you time. Also nobody really thinks QM is the end of
| it, assuming semi classical physics under the hood is just
| odd to me. There is something below QM that we don't
| understand yet (AdS/CFT looks like a good start to me) and
| personally I think the whole interpretation of QM debate
| will look stupid in retrospect. Yeah collapse is odd, but
| it just shows us this isn't it. Reality is much weirder
| than we thought and giving up on realism is just the
| beginning.
| jobs_throwaway wrote:
| > No one in the whole world cares if the universe is
| deterministic or not
|
| lol
| tsimionescu wrote:
| Actually, if you eliminate collapse entirely as a non-
| linear operation, then you have a new huge problem for QM:
| there is plenty of non-linearity in the universe (e.g.
| double pendulum experiments, not to mention GR), and QM
| predicts that there shouldn't be any non-linearity at all,
| if you eliminate wave function collapse/the Born postulate.
| GoblinSlayer wrote:
| Hmm... is de Broglie wave linear? Trigonometric functions
| don't look very linear to me.
| macrolocal wrote:
| Eh, these are models, not reality. The Many-Worlds
| interpretation makes the fewest assumptions, so it's probably
| the least prone to over-fitting.
|
| Until we find philosophically or experimentally distinguished
| ways to pare down its ontological cost, working with most
| general theory is just keeping an open mind.
| lupire wrote:
| Disproving some form of _measurable_ wave function does not
| provide evidence for MWI, which is unmeasurable and untestable
| nearly by definition.
| Diggsey wrote:
| Only if you assert that the other worlds are in some way
| "real". See https://en.wikipedia.org/wiki/Many-
| worlds_interpretation#Deb...
|
| The MWI is a simpler theory than other interpretations
| because it does not require "collapse" to be a physical
| process. The "realness" of the other worlds is untestable,
| but also not part of the theory.
|
| "unreal" MWI should be the null hypothesis given what we know
| to be true about quantum mechanics. If we find evidence that
| collapse is a physical process then we can reject it, but
| otherwise it makes the fewest leaps. At the moment the
| Copenhagen intepretation is taught instead, which is a
| problem. To quote wikipedia:
|
| > There is no uniquely definitive statement of the Copenhagen
| interpretation
|
| And
|
| > the device used to observe a system must be described in
| classical language, while the system under observation is
| treated in quantum terms
|
| In other words, it does allow you to predict the result of an
| experiment, but we know it can't be right because it's
| impossible to formalize without building this "classical
| observer" into the model. Attempting to build on this
| inevitably leads to metaphysical nonsense about
| consciousness.
|
| In "unreal" MWI there is a universal wave function, and
| something is "real" to us if it is entangled with us. The
| "many worlds" terminology makes it easier to visualize but
| doesn't mean those other worlds are real because whether
| something is real is subjective in this interpretation.
| Subjective reality may be a problem for some people, but if
| you look at the evolution of physical theories, we
| consistently find that everything is more subjective than we
| thought it was (see also: relativity).
| c1ccccc1 wrote:
| Wait, I'm pretty sure that if these measurements had shown a
| collapse, that would have to be taken as disproving many
| worlds. You can't very well have many worlds when your
| wavefunction is physically collapsing all the time before
| those worlds can diverge. So it is actually kind of testable,
| since a test was just performed that could have ruled it out.
| Maybe you're saying that it's untestable relative to
| _unmeasurable_ collapses of the wavefunction. But if those
| collapses are contrived to be unmeasurable, doesn 't that
| make them kind of, well, pointless?
| fallingfrog wrote:
| Well, the thing is that the MWI is actually simpler than all
| the other interpretations, because it simply removes the idea
| of wave function collapse entirely. Any theory involving wave
| function collapse is adding something _extra_ to quantum
| physics that can 't be demonstrated experimentally.
|
| Because we live in the macro world, it _feels_ like a single
| unitary reality is simpler, but actually, the MWI makes fewer
| assumptions. So I would turn that around and put the burden
| on the _other_ theories to show that collapse is real, the
| default position should be MWI.
| lamontcg wrote:
| > Any theory involving wave function collapse is adding
| something extra to quantum physics that can't be
| demonstrated experimentally.
|
| Title article is literally about trying to test those
| theories experimentally.
| fallingfrog wrote:
| ..And failing to find any evidence of collapse. Hence
| "can't be demonstrated". I didn't mean "can't be looked
| for" I meant that attempts to find it have not been
| successful.
| TheOtherHobbes wrote:
| You don't think postulating an unknown number of extra
| universes with a very poorly defined relationship with each
| other qualifies as an extra assumption?
| pdonis wrote:
| The MWI does not postulate extra universes, although that
| pop science description is unfortunately common even
| though it is wrong. The MWI just says that the one
| universe that exists is actually very, very different
| from what we perceive. (To be clear, I'm not saying this
| correct description makes the MWI any more palatable. I
| am just clarifying exactly what kind of unpalatableness
| the MWI requires.)
| ryeights wrote:
| Can you elaborate on this? The Wikipedia page for MWI
| says
|
| >The many-worlds interpretation implies that there are
| most likely an uncountably infinite number of universes.
|
| https://en.wikipedia.org/wiki/Many-worlds_interpretation
| d_tr wrote:
| Not the parent, but I 'd say this amounts to how you
| define a "universe". There is a single wavefunction which
| says that one "copy" of you observes result A and another
| "copy" observes result B. Using the phrase "many
| universes" implies that these two scenarios are
| considered as "different universes". I personally do not
| like this phrase and find it misleading.
| TEP_Kim_Il_Sung wrote:
| You are all the "copies", and, under certain conditions,
| can experience all their observations. Think of yourself
| more as an aspect of a multifaceted being experiencing
| the universe through you.
| pdonis wrote:
| _> under certain conditions, can experience all their
| observations_
|
| What conditions are these?
| olddustytrail wrote:
| Let's say we generally subscribed to the flat earth
| theory. But that causes many problems with our actual
| measurements. So someone proposes the "many earths"
| theory, where there are many flat earths connected at
| different angles.
|
| If you could travel between these many earths, you could
| even end up in one - let's call this mythical land
| "Australia" - where South was up!
|
| Sounds a bit crazy but some people believe it could
| really exist.
| GoblinSlayer wrote:
| Those worlds are states in superposition, the term
| "world" is an allegory to help people understand that
| those states don't interact due to linearity of the
| Schrodinger equation, because not all properties of
| linearity are obvious.
| pdonis wrote:
| One should not be trying to learn physics from Wikipedia,
| particularly not for something as complicated as QM, even
| more particularly not for an aspect of QM as contentious
| as the MWI.
|
| The MWI says that there is one single universal wave
| function, which evolves in time by unitary evolution
| forever, and that that universal wave function is all
| that exists. That is one universe, not an infinity of
| them. It is just one universe that is nothing like what
| we think we perceive.
| GoblinSlayer wrote:
| We perceived flat earth and geocentrism, so not the first
| time. I can recommend quantum electrodynamics to people
| who are too attached to corpuscular paradigm.
| kgwgk wrote:
| "The MWI" is not one thing. There are many-people saying
| many-things about those many-worls.
| d_tr wrote:
| It is the other way around. The "universes" are there
| when you solve the equations, and you can either let them
| be or keep only one by invoking the collapse.
|
| The collapse amounts to just setting some terms to zero.
| sfink wrote:
| Only to the extent that MWI is actually a _position_. My
| understanding of MWI is: shit happens, and there 's no need
| to understand why specific shit happens because all shit
| "happens" (by a definition of "happens" that carries
| basically no meaning) and you should be happy just to prove
| that the shit that happens is among the full set of shit
| that could happen. It's the "don't worry your pretty little
| head over it" theory of reality.
|
| Here's the best poem ever written, or that will ever be
| written: Roses are red Violets
| are blue MWI stinks And so do you.
|
| Don't think it's that great? Well, that's because there
| exist other versions of me that wrote different words up
| there, and you just happened to read a version that wasn't
| that great.
|
| I hereby accept my position as God Poet of the Universe.
| GoblinSlayer wrote:
| Shit happens because that's how the state of matter
| changes over time, the wave function is the description
| of the state and the Schrodinger equation is the
| description of the state's change. That's as complete and
| happy understanding as it goes.
| tsimionescu wrote:
| It is not simpler, since MWI still needs the Born postulate
| to actually predict the results of quantum experiments. It
| replaces this idea of the wave function collapsing with a
| redefinition of what a measurement apparatus / observer is
| (in MWI, a measurement apparatus exists in a single
| "branch" of the wave function).
|
| This is especially problematic because QM doesn't predict
| any particular decomposition of a quantum state into
| particular classical states. That is, the Schrodinger
| equation doesn't actually predict that a particle has some
| amplitude here and some other amplitude there, as is often
| presented; instead, it predicts that it is described by
| some vector which can be decomposed in many different ways.
| You can say it has some amplitude X here and some amplitude
| Y there, but with any 2 points in space-time (adjusting the
| amplitudes). Or, it can have some combination of position
| and spin with amplitude X, and some other combination of
| position and spin with amplitude Y. You can choose any
| basis you like for the measurement, and you will get the
| corresponding answer.
|
| But, for MWI to actually predict experimental results (and
| the classical world we live in) you not only have to choose
| to look at a single element of that basis, but you also
| have to believe that the classical basis is somehow
| preferred.
| GoblinSlayer wrote:
| >This is especially problematic because QM doesn't
| predict any particular decomposition of a quantum state
| into particular classical states.
|
| It does predict it, this decomposition is called
| decoherence, where a classical state splits into a
| superposition of several different classical states.
| pdonis wrote:
| _> this decomposition is called decoherence, where a
| classical state splits into a superposition of several
| different classical states._
|
| No, that's not what decoherence is. Decoherence is the
| spread of entanglement over a very large number of
| untrackable degrees of freedom (usually referred to as
| the "environment"). This makes interference effects
| unobservable. But decoherence itself does not involve any
| "splitting"; the entanglement that decoherence spreads
| over a very large number of untrackable degrees of
| freedom has to already be there before decoherence can
| act on it.
| GoblinSlayer wrote:
| AFAIK the largest molecule to show quantum behavior in
| experiments is somewhere at 100 atoms. I suppose that's
| all "environment" you need for a large number of degrees
| of freedom.
|
| And yes, spread of entanglement does mean splitting.
| Entangled state is not factorizable, because all states
| in it are split. This splitting is the result of
| splitting of the initial state.
| pdonis wrote:
| _> I suppose that 's all "environment" you need for a
| large number of degrees of freedom._
|
| No. The 100 atoms is the largest molecule that we can do
| experiments on _without_ having decoherence happen and
| ruining our attempts to observe interference.
|
| The number of degrees of freedom in the environment is
| many orders of magnitude larger, something like 10^30 or
| more for a typical experiment.
| [deleted]
| lebuffon wrote:
| Don't tell anyone, but in the back of my mind I wonder if what we
| call quantum mechanics has something to do with the rendering
| engine in this simulation we find ourselves in.
|
| Is quantum collapse just us "catching" the engine deciding what
| to render when we observe something? :-)
| licnep wrote:
| I have very little knowledge of quantum physics, but in my mind
| there is some similarity between quantum phenomena and backward
| raytracing in computer graphics.
|
| In forward raytracing, images are rendered by "shooting"
| photons from all lightsources and seeing which ones end up
| hitting the player's camera. This is similar to what we think
| happens in nature, but the calculation is extremely
| inefficient, because the vast majority of photons never hit the
| player's viewpoint.
|
| In backward raytracing, we only shoot "photons" backwards from
| the player's camera, and see which rays end up hitting a light
| source. This computation is much more efficient.
|
| It makes me wonder if our "simulation" uses a similar shortcut
| phailhaus wrote:
| That's my interpretation as well, except I'd go a step further
| and say it's time-independent based on what we've seen of
| quantum entanglement. There's no reason to resolve a particle's
| state if it's not interacting with anything, but once you do
| you can safely define the entangled pair's state retroactively
| because it hasn't interacted with anything either.
|
| So what we end up seeing is that after you measure one
| particle, the other _behaves as if it always had the
| complementary value_. It 's not faster-than-light spooky action
| at a distance, it's more akin to reality "resolving" to a
| consistent time-independent state.
| macrolocal wrote:
| Maybe, but it would be a highly non-classical computer.
| Probably it could cheaply render the most physically plausible
| paths to specified outcomes, and quickly factor large primes.
|
| Nb. quantum also highlights assumptions made by our brain's
| rendering engine.
| axilmar wrote:
| Perhaps the collapse happens when all the quantum fields are
| activated at a particular point in their coordinate system.
|
| I.e. if we have 3 fields, with respective coordinates [0, 1, 2],
| [1, 2, 3] and [2, 3, 4], a particle emerges only when the 3rd
| point of field A, the 2nd point of field B and the 1st point of
| field C, all with value = 2, are activated.
|
| If the quantum field activations happen periodically, but their
| periods do not match, or the fields have different granularity
| when they are activated, then we may get a wave-like outcome for
| particles, since the interactions of all the fields happen only
| when the fields are synchronized at specific points in their
| history.
|
| EDIT:
|
| Writing the above made me realize that the underlying fabrique of
| the universe may work like a neural net, where each possible
| point in the universe is actually a node in a neural net, and
| each node has multiple fields connected to each node, and values
| flowing into the fields excite the nodes based on a function, for
| example accumulation. When a limit is exceeded in a node, a
| particle is created, or a particle disappears (for black holes).
|
| A neural net of such proportions could be called ...God (yeah, I
| said it, sorry...I don't believe in a God but the parallelism is
| interesting, at least to me, from a philosophical perspective).
| im3w1l wrote:
| In true collapse-of-the-gaps style, what if collapse happens when
| an entangled system becomes so large that the edges of it are
| outside of each others event horizons due to cosmic inflation?
| rocqua wrote:
| Why would that force collapse? I would almost expect that the
| lack of communication over those distances forces _more_
| uncertainty (i.e. a wider probability distribution) rather than
| less uncertainty.
| im3w1l wrote:
| It's kind of a joke, which is what I meant by -of-the-gaps.
| If two particles are outside of each others event horizons,
| they can't communicate so you can't tell whether they are
| entangled (AA or BB) or whether the system has collapsed into
| say AA.
| bowsamic wrote:
| I think you mean expansion rather than inflation (inflation is
| something that happened very briefly at the beginning of the
| universe). In models with collapse, the collapse happens
| instantaneously, no matter what
| cb321 wrote:
| As with any unsettled questions there are pros & cons to the
| various takes on quantum reality. Part of the appeal of MWI
| (intrication of observer into observed system as part of the
| measurement process) to me was always that the
| instantaneousness you mention here is a very "ordinary" kind
| of "fastness by synchronization". It's basically just a kind
| of causal wavefront hitting.
|
| There are plenty of "infinitely fast" synchronization effects
| like this..some perhaps less obvious than others, but many
| pretty pedestrian and accessible to lay people. Neither the
| junction of a scissors or the "spot light" on clouds need be
| constrained by light speed, for example. People routinely
| abuse "nothing" (or maybe "go") in the " 'nothing' can 'go'
| faster than light" saying. :-)
| kgwgk wrote:
| > intrication of observer into observed system as part of
| the measurement process
|
| That was already part of von Neumann's model of measurement
| over 90 years ago.
| cb321 wrote:
| Yeah. Perhaps most charmingly treated here:
| https://arxiv.org/abs/2011.12671 { EDIT: though surely
| many other places! There are also YouTube videos of this
| one, though, and Sidney Coleman was really a Feynman-
| class edutainer, perhaps as under-recognized as von
| Neumann is relative to say Everett on this topic :-) }.
|
| I should perhaps have used the word "entanglement" rather
| than "intrication". Oops.
| gus_massa wrote:
| If you have only one particle of the entangled pair, you can't
| do any experiment to check if they pair is still entangled or
| someone else has done something to the other particle and broke
| the entanglement. Someone else is not necessarily a person. May
| be a device or just a brick.
|
| In a common case, when you measure your particle you get 50%
| "yes" and 50% "no". So if you have a stream of particles that
| are one half of an entangled pair, you just get a random
| sequence.
|
| It doesn't matter if the other half is still flying happily in
| vacuum, got into a detector like the one you have, or it just
| hit a wall. You just get a random sequence. Otherwise, it could
| be used to build a FTL "walkie talkie".
|
| If you later can talk with someone in the other side that
| measured the other half of the pairs, then both of you can
| compare notes and notice that the two random sequences are
| equal or oposite or something in between according to which
| experiment each of you have done.
| im3w1l wrote:
| Dang I low key have a problem here because I already
| mentioned it was a joke and gave the same explanation, but
| because this is the top reply and the comments both show
| n-hours ago it looks like I walked back my statement in
| response, and I think it's fair to say that this is why the
| original comment got a down vote and ended up at the bottom.
| gus_massa wrote:
| After reading your comment again, now I'm wondering how
| does the variation of QM discussed in the article handle
| the special cases you mentioned.
|
| In the usual QM the explanation is "easy" because the
| collapse is magical.
|
| But if they want to eliminate the magic and propose a
| underlying "physical" process for the collapse then they
| have nasty problems and FTL transmission.
| mkaic wrote:
| Looking forward to the PBS Spacetime coverage of these
| experiments in about 2 weeks time, I'm sure they'll do an
| excellent job explaining them.
| markisus wrote:
| This tidbit about a prodigious undergraduate struck me. He double
| majored in math and physics and was about to start his PhD at
| Harvard. And in a sudden freak accident he was gone from
| existence. The universe will always remain unfathomable in some
| ways.
|
| > In 1996, Qijia Fu of Hamilton College in New York -- then just
| an undergraduate -- proposed using germanium-based neutrino
| experiments to detect a CSL signature of X-ray emission. (Weeks
| after he submitted his paper, he was struck by lightning on a
| hiking trip in Utah and killed.)
| whimsicalism wrote:
| Seems perfectly fathomable to me.
| addaon wrote:
| Reminds me of a golden age (?) science fiction short story --
| no idea the author or name -- about a spate of suicides and
| mysterious deaths among physicists who got too close to "the
| truth," externally caused by an alien force trying to keep
| humans in their petri dish.
| cbruns wrote:
| Sounds like Three Body Problem. Not golden age though.
| abecedarius wrote:
| It's an Asimov story whose title I forget. The truth in
| question was a defense against nuclear bombs.
| HALtheWise wrote:
| Breeds There a Man...?
|
| https://en.wikipedia.org/wiki/Breeds_There_a_Man...%3F
| addaon wrote:
| That's it! Thanks!
|
| Clearly left a mark on my memory.
| royaltheartist wrote:
| Oh great, now they've got Doom running at the Quantum level
| EGreg wrote:
| I like PWT because other theories don't rule out FTL propagation
| of things, either, and PWT just assumes it. It is far less weird
| than for example the many worlds explanation.
| gus_massa wrote:
| Note that this was not the "mainstream" explanation. It was not
| even the most popular explanation.
|
| Everyone agree about the math, but there are a few
| interpretations of quantum mechanics. All are weird and
| equivalente, so it's not possible to make an experiment to decide
| which one is the correct one.
|
| There are a few attempt like this to extend QM and get a less
| weird theory, but it looks like this failed, at least with the
| more simple model for the extension. Anyway, most people just use
| "Shut up and calculate".
| bowsamic wrote:
| I have a PhD in theoretical quantum optics and I can assure you
| that it absolutely was (and still is) a mainstream explanation
|
| EDIT: I misread the article, I thought it was about whether
| collapse occurs in general, not about physical explanations for
| collapse
| pfortuny wrote:
| Yep: the article seems to say "there is no collapse" (in the
| title) but then it turns out to say "collapse as explained by
| these models may not be". Two very different things. I was
| caught as you by the title.
| gus_massa wrote:
| I was initially confused too.
| lupire wrote:
| Please explain the mistake in the article.
|
| > The experiments find no evidence of the effects predicted
| by at _least the simplest varieties_ of these collapse
| models.
| pfortuny wrote:
| No, the mistake is in the _natural interpretation of the
| title_. The title seems to imply "collapse is not a
| thing", whereas the article is about "these explanations of
| collapse do not hold".
| bowsamic wrote:
| I have no idea, sorry
| awinter-py wrote:
| ugh the actual news event being covered in this article is a 2022
| result[1] confirming a 2020 result[2] both of which 'set a lower
| bound' on this theory by penrose. 'set a lower bound' means they
| didn't find it.
|
| this article is credulous -- yes, this _may_ exist and semi-
| serious people are looking for it, but pls don 't confuse 'we
| haven't found it yet' with 'current science suggests this is very
| small'.
|
| how small?! at least admit that your theory doesn't predict an
| energy level. 'Current science suggests that bigfoot dwells in
| the places we have not yet looked'. Also put the newest paper in
| the first paragraph, don't make me dig through recirc links, ugh.
|
| 1.
| https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.12...
|
| 2. https://www.nature.com/articles/s41567-020-1008-4
| [deleted]
| stevenally wrote:
| Quantum mechanics is a useful model in some contexts. It is not
| reality.
|
| Other models are useful in other contexts.
|
| Reality is unknownable. But we can always use better models.
| iNic wrote:
| "The map is not the territory" - Korzybski
| hilbert42 wrote:
| _" If there is indeed a background perturbation that provokes
| quantum collapse -- whether it comes from gravitational effects
| or something else -- then all particles will be continuously
| interacting with this perturbation, whether they are in a
| superposition or not."_
|
| This makes eminent sense to me.
|
| I have a notion that I'll try to present in its simplest form
| which is that a quantum system exists in background 'sea' or
| 'substrate' akin to random noise whose maximum fluctuations are
| of themselves insufficient to disturb or perturb said quantum
| system.
|
| Without this noise an 'event' such as a particle, photon etc.
| would perturb the quantum system in a predictable way thus it
| would 'collapse' into a predictable outcome (according to
| understood physics).
|
| As the noisy substrate permeates and superimposes on everything
| it randomizes the 'collapse'. Of course, we'd have to invoke
| notions such as virtual particles zero point energy, Casimir-like
| effects--even then, saying that is a gross oversimplification
| without much additional amplification. Perhaps it's best just to
| say that essentially a noisy fluctuating background environment
| would perturb and randomize an otherwise predictable quantum
| system.
|
| Again, like many of these theories, I've little to support my
| idea except intuition--and with quantum mechanics relying on it
| is a very dangerous thing to do.
| vpfaulkner wrote:
| From a layman's point of view, it seems like we grasping at
| straws when it comes to these thorny quantum questions. Is fair
| to say, for example, that we are about as clueless as our
| ancestors were with the bubonic plague?
|
| To a non-expert it can be difficult to separate which theories
| lay on solid ground and which theories are highly speculative.
| resoluteteeth wrote:
| > From a layman's point of view, it seems like we grasping at
| straws when it comes to these thorny quantum questions. Is fair
| to say, for example, that we are about as clueless as our
| ancestors were with the bubonic plague?
|
| > To a non-expert it can be difficult to separate which
| theories lay on solid ground and which theories are highly
| speculative.
|
| Sure, but isn't that the point of doing these experiments?
| vpfaulkner wrote:
| I'm all for trying to understand these phenomena and running
| these experiments. Just trying to get a sense for how much of
| a grasp we have on these phenomena.
|
| Based on the other responses, it seems like we can
| mathematically model these phenomena very well and make very
| good predictions. However, when it comes to explaining why
| these phenomena exist in the first place, we are like a
| medieval doctor trying to explain why antibiotics work.
| ravi-delia wrote:
| That would not be fair, though it's understandable why a layman
| might feel that way. The fact is, most physicists don't
| particularly feel the need to have an explanation for that kind
| of thing. We have the math, and most people agree on how to use
| it to make very accurate predictions. Collapse was always a
| little silly, but there are other possibilities as to why you'd
| get that kind of effect just from wavefunctions.
| bee_rider wrote:
| "It's only a model" Patsy says, but then they cut to a whole
| big song and dance routine, so it must be a pretty good
| model. Or course it is unsurprising that Monty Python's Holy
| Grail would provide deep physics insights, they were a pretty
| clever bunch.
| whimsicalism wrote:
| It's like we had miasma theory of disease, but miasma theory
| was actually highly accurate at predicting disease.
|
| So... not really like how our past misunderstanding of disease,
| which was useless as well as being wrong.
| lamontcg wrote:
| > which theories are highly speculative.
|
| So QM itself is on very, very solid ground. You're using it now
| on your computer.
|
| The interpretations of QM and the attempts to reconcile the
| exceptionally well tested mathematics of QM and the reality
| that we experience which is not-QM at all are all philosophical
| with zero evidence. Everyone just tries to make compelling
| arguments based on things like Occam's razor about why their
| horse is the best one in the race without actually knowing
| anything at all.
|
| We have place a few bounds around things like Bell's inequality
| so we know that local hidden variable theories are ruled out,
| but that is about it.
|
| The title article is very interesting because its one of the
| first few actual tests to probe if there really is a transition
| between QM reality and classical reality. Regardless of who
| actually wins the horse-race the important thing here is that
| there's slow progress being made on trying to experimentally
| test theories. This is why I've always liked the Penrose models
| of collapse better than the MWI models since the former have
| some chance of being actually testable, while with MWI you just
| blindly decide it is true or not and then you argue a bunch
| about philosophy and never do any experiments, which isn't
| science. Penrose models of collapse might be wrong but at least
| they're in principle testable, which is incredibly exciting
| about this article.
| c1ccccc1 wrote:
| Many worlds is absolutely testable, since if we observe
| collapse in even a single one of these experiments then that
| completely falsifies many worlds. If one of these experiments
| discussed in the article had actually observed a collapse,
| then I have no doubt we'd be seeing headlines like "many
| worlds theory disproven", and Nobel prizes for the physicists
| involved. It would be the biggest discovery in physics for
| decades.
| lamontcg wrote:
| You don't get there from WMI though. You get there from
| trying to prove collapse happens and testing some other
| theories predictions.
| simonh wrote:
| QM is hard to visualise, but we have extremely sophisticated
| equations and principles for determining how quantum systems
| will evolve, and can engineer complex functioning systems using
| that knowledge. For example transistors only work because we
| understand QM well enough to precisely engineer the energy
| level state behaviour of electrons in semiconductors.
|
| It would be like accidentally discovering antibiotics during
| the plague. You might not know how it works or why, but you
| know what it does and it absolutely gets the job done.
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