[HN Gopher] Can the double-slit experiment distinguish between q...
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Can the double-slit experiment distinguish between quantum
interpretations?
Author : elashri
Score : 66 points
Date : 2023-01-09 16:21 UTC (6 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| alberth wrote:
| Still the best video I've ever found that describes the
| phenomenon of the double-slit experiment.
|
| Cartoon by "Dr Quantum"
|
| https://www.youtube.com/watch?v=Bq69-MI9TA0
| alberth wrote:
| For all the downvotes I'm getting, no one has still linked to a
| better video that's easy for general audience to understand.
| Strilanc wrote:
| This video is very misleading.
|
| - It shows the single-slit case as a vertical band. Actually,
| the single slit case is also a smear[1][2]. A smear just a wide
| as the double slit pattern (but less rippled). Photons don't
| switch between moving like bullets and moving like waves, they
| consistently move like waves and consistently hit like bullets.
|
| - It shows the photon detector as an eye off to the side of the
| experiment. You gotta stick it in the beam path for it to
| interact with the photon. You can't see photon flying by in
| front of you, you can only see photons bounced into your eye.
| Note that I'm not saying the detector has to absorb the photon,
| but it does have to interact with the photon and it can't
| interact with the photon if it's way off to the side like that.
|
| Ultimately, it's playing into the common misunderstanding that
| a human glancing towards a quantum experiment has some profound
| effect upon it.
|
| 1: https://www.youtube.com/watch?v=h53PCmEMAGo
|
| 2: http://backreaction.blogspot.com/2021/10/the-delayed-
| choice-...
| mensetmanusman wrote:
| Why isn't the slit material edge itself a detector since it
| must be interacting with the photon?
| lazide wrote:
| Photons that interact with the edge go through a different
| process of absorption and re-emission + scattering (or
| not). They aren't the original photon.
| mensetmanusman wrote:
| That's true of the air the photon is traveling through
| though...
| OkayPhysicist wrote:
| IMO, detection/observation is the wrong framing of the
| problem. A better approach is about _consistency_. All
| interactions in a system must be consistent: if you have
| two Schrodinger 's cat-boxes being controlled by the same
| measurement, then either both cats will be dead, or both
| will be alive, you will never find one dead and the other
| alive.
|
| In an experimental setup, you might have many different
| levels of interaction: the photon either hits one sensor or
| another, that results in one or another message being sent
| to your recording device, which records one or the other
| result on your harddrive, etc. As the scale goes up, more
| and more stuff gets dependent on the result of your
| measurement, until eventually _everything_ is, yourself
| included. And if everything is dependent on the result of
| your experiment, they must all be consistent with a given
| result of your experiment. Thus, you end up with exactly
| one answer.
|
| Since the slit edge isn't changed by the diffraction of
| light, there is no inconsistency between whether the photon
| passed through its slit or the other.
| alberth wrote:
| I really appreciate you linking to this video, and did enjoy
| it.
|
| I still believe the video I linked to is the best for a
| general audience.
|
| I'm not sure someone without prior knowledge would follow
| that video.
| jjbinx007 wrote:
| Oh god no. That video is very misleading and pretty much
| borders on pseudo-science.
|
| For starters it depicts photons as balls, when it would be much
| less confusing and more intuitive to instead think of them as
| waves with discreet energy amounts. If you think about it as a
| wave, what's happening is a wave with a photon-amount of energy
| passes through both slits which causes an interference pattern.
| When it hits the wall it coalesces into a single particle/dot.
|
| Also, it talks about 'observer' and strongly indicates the
| observer needs to be a conscious entity. Instead of observer,
| just use the word "detector", and bear in mind that detector
| interacts with the photon (whereas at the classical level you
| can watch or observe something without affecting the system).
| alberth wrote:
| Would you mind linking to a better video, suitable for a
| general audience.
|
| The difficulty is most video are either _way_ to technical or
| way too high-level.
| jjbinx007 wrote:
| I recommend videos by Arvin Ash. He's one of the few who
| manages to explain things in a way that makes sense to me.
| A lot of Youtube videos either parrot the pop-sci
| explanations I get tired of reading in magazines or they're
| way above my head.
| zmgsabst wrote:
| A small point:
|
| A finitely bounded wave is better described as a wavelet.
|
| https://en.wikipedia.org/wiki/Wavelet
|
| Particles are the wavelets that when summed, give us the
| field as a whole, ie, particles are the wavelet transform of
| a field.
| criddell wrote:
| The video talks about shooting electrons rather than photons
| through the slits. Does it matter what kind of particle you
| shoot through? If I fired a stream of hydrogen atoms or
| neutrons through the slit, would I get an interference
| pattern?
|
| I've also always wondered if it matters what side of the
| slits the detector is on? The experiment as depicted in that
| video has the detector on the gun side of the slits. Would
| you get the same thing if you moved it to the wall side of
| the slits? Also, does the wall itself count as a
| detector/observer?
| PeterisP wrote:
| The effect applies to all particles, but it does matter
| what kind of particle you shoot because the sizes involved
| become very different. Apparently, the effect has been
| demonstrated even with molecules of 2000-ish atoms -
| https://www.nature.com/articles/s41567-019-0663-9
| Lerc wrote:
| I'm not sure if detector is any better than observer. Isn't
| it the issue of when does it collapse/decide (also
| problematic terms) rather than the multiple options
| propagating into the detector? Observer get used because at
| least then someone is experiencing the decision. Many worlds
| punts on that option by making a new observer world each way.
|
| I'm a layperson who reads a bit so I could be
| misinterpreting. I was always partial to the idea of
| probabilistic squeezing rather than collapse. In the absence
| of quantum gravity, probabilities can propagate only as far
| as their gravitational effects allow. As particles interact
| the compatible possible positions reduces to eventually
| squeeze the location to an infinitesimal size. It may be
| utterly wrong as an idea but it would negate the need for
| observers, detectors, or many worlds which makes it a bit
| compelling.
| [deleted]
| chedca21 wrote:
| [flagged]
| elmomle wrote:
| Could you explain the connection between these two statements?
| rsstack wrote:
| If you see something absurd in a HN comment, it's worthwhile
| to check their comment history. You aren't missing anything
| or miscomprehending - it's just a troll.
| lucisferre wrote:
| Yes the OP doesn't understand the first one therefore the
| second one might be false.
|
| QED.
| a257 wrote:
| High energy EM radiation is able to ionize atoms through the
| photoelectric effect. Cellphone radiation is unable to do this
| because it doesn't have enough energy. This is strictly the
| case because energy in these scales are quantized.
| red_trumpet wrote:
| By high energy you mean low wavelength, right? Because also
| large wavelengths could transmit a high amount of energy.
| PartiallyTyped wrote:
| If you don't like the theoretical explanation given in the
| sibling comment regarding energy carried by photons, try an
| experimental approach and get back to us with your results.
| konschubert wrote:
| I wish I could have studied Physics in 2050 when the Copenhagen
| Interpretation was already dead.
|
| Or maybe I should have stuck around to move the science along. I
| didn't have the grit for that
| drowsspa wrote:
| If my experience in Physics is somewhat typical, it's barely
| taught as an interpretation, it's just as Feynman put it "shut
| up and calculate".
| konschubert wrote:
| True.
|
| And I'm not saying we should be having philosophical
| discussions.
|
| But pretending that there isn't a problem with the copenhagen
| interpretation is also an insult to the students intellect.
| analog31 wrote:
| We were certainly more than aware of the problems. They
| even brought in colloquium speakers to talk about it.
| konschubert wrote:
| I don't remember this being discussed at my alma mater.
| Not in lectures and not in colloquia. But then again,
| maybe it happened and I missed it. I don't want to throw
| shade.
| pdonis wrote:
| The paper goes astray in my view right at the start, when it
| points out that time is a parameter in the Schrodinger equation,
| not an operator, so that equation gives no way to uniquely derive
| a probability distribution for measurement results as a function
| of time--but then fails to note the solution to that problem,
| which is to not use the Schrodinger equation in the first place.
| The correct framework in which to treat time on the same footing
| as other observables is relativistic quantum field theory. That
| is never even mentioned in this paper.
|
| (To be fair, I have never seen _any_ discussion or comparison of
| QM interpretations that uses QFT as its framework; they all use
| non-relativistic QM, even though we know that 's just an
| approximation. But it's still an issue even if it's an extremely
| common one.)
| eternalban wrote:
| [flagged]
| ajross wrote:
| Can someone in the physics community give us the consensus
| summary of whether this is serious/real/non-BS? Seems like this
| would be an absolutely earth-shattering theory result (especially
| since they claim it's verifiable with a feasible experiment),
| which seems hard to judge from outside based on the paper itself.
| Are people buying this, or are there questions?
| sounds wrote:
| I think what's being asked is if this is the best way to
| formulate a testable hypothesis.
|
| It seems to pass a first scan here.
| scythe wrote:
| It's not earth-shattering for _theory_ , I can tell you that
| for sure. If you read the citations of the paper, you'll find
| that Das, Noth and Durr already proposed something similar in
| 2019 which was published in _Phys. Rev. A_ , one of the most
| respected journals. What these authors are doing is basically
| to propose a refined (and _possibly_ more general) experimental
| setup. Whether this actually works out in practice, or even
| represents a particularly good way to go about it, is beyond my
| fluency in this field; I would guess the practical effect is
| incremental at best.
| ko27 wrote:
| It's earth-shattering, because the current prevailing opinion
| in physics is that some of those QM interpretations are
| indistinguishable in reality and that their difference is
| only a matter of philosophy.
| mh7 wrote:
| It's probably a case of me not knowing what I don't know, but
| I've never understood what the big deal with 'observation' is in
| QM. I dabble a lot in electronics and I'm painfully aware of how
| measurements affect a circuit - try to measure current and you
| introduce a voltage drop, stick a probe somewhere and you add an
| antenna, add capacitance, etc.
|
| So to me when trying to measure anything it seems so blatantly
| obvious that it has to change the outcome - you will interact in
| some way with the system to get any information out, and this
| will change the tracejctory, energy, momentum or whatever of the
| particles.
|
| I mean is that it? That's the mystery?
| EliRivers wrote:
| In your examples interacting with a circuit, you affect what
| you're observing because you have physically changed it. You
| have poked it with a metal stick and you have physically
| changed the system you are observing.
|
| With QM, it's _NOT_ that you are poking it with a stick. It 's
| _NOT_ that you are physically interacting with the system and
| physically changing it because you 've poked it with a stick
| (be it literally or metaphorically).
|
| With QM, having knowledge of the system is what changes it.
| Observing it is what changes it; not some physical change you
| make to the system because you're poking it with a tool. The
| fact that it is observed is what changes it.
|
| Having knowledge about the system changes it, no matter how you
| got that knowledge, even if you got that knowledge in a way
| that cannot possibly have physically affected the system.
| zeroonetwothree wrote:
| It's not "knowledge" that changes it--this seems to give some
| mystical power to human minds. It's that it interacts with
| the "outside world", ie decoherence. Which isn't very magical
| in itself.
| EliRivers wrote:
| By "knowledge", I include any kind of record. Anything.
| Something different in the universe. Even if nobody
| actually looked at it, even if it wasn't actually recorded.
| Not magical human minds indeed; just that the measurement
| happened. Information created. However we like to word it.
| English isn't a great language for this. I suspect no
| language really suits.
|
| _Which isn't very magical in itself._
|
| Well, it's also supremely magical. That's the whole
| weirdness of it all.
| zeroonetwothree wrote:
| I don't think decoherence is magical, indeed it's what
| happens every day all the time such that we never
| perceive quantum effects in our everyday lives!
| rsp1984 wrote:
| _even if you got that knowledge in a way that cannot possibly
| have physically affected the system._
|
| How can that be possible? Any examples?
| TheOtherHobbes wrote:
| https://en.wikipedia.org/wiki/Elitzur%E2%80%93Vaidman_bomb_
| t...
| changoplatanero wrote:
| Imagine you set up Schrodinger's cat experiment where you have
| a photon pass through a double slit and if it goes through the
| left slit then it electrocutes the cat in the box and if it
| goes through the right slit then the cat is spared. You set up
| the experiment and leave the box for two days and then come
| open it to "measure" if the cat is alive or dead. The mystery
| is that its hard to understand how performing the measurement
| of opening the box can change the outcome of seeing a healthy
| cat or one that's been dead for two days.
| DontchaKnowit wrote:
| It very obviously does not change yhe outcome here right?
| This is an odd example
| changoplatanero wrote:
| The fact that checking on the cat is obviously unrelated to
| the path of the photon is what makes it an interesting
| example of how quantum mechanics is different from ordinary
| intuition.
| DontchaKnowit wrote:
| I see. Makes sense.
|
| I still refuse to believe the unintuitive interpretations
| of QM. I am a show me stater, after all. (Only kind if
| joking)
| awb wrote:
| Einstein would have agreed with you
| mongol wrote:
| I don't get it. At what point in this hypothetical experiment
| did the photon pass one of the slits? Two days before you
| open the box?
| changoplatanero wrote:
| Yes
| zeroonetwothree wrote:
| This example isn't very compelling because we might as well
| say the cat died two days ago you just found out later.
| dinkumthinkum wrote:
| No, it's not like sticking a voltmeter on a circuit. The double
| slit experiment definitely does not show something obvious. If
| you look into it a bit more about the wave function collapse,
| you will see very surprising results, if you are not familiar
| with it. I never heard anyone say it was obvious when they
| learned it. :)
| ko27 wrote:
| If you read up on the Delayed-choice quantum eraser experiment
| [1] you'll see how your "simplistic" explanation leads to
| paradoxes such as the present altering events that occurred in
| the past. But if you describe unmeasured states as being in a
| superposition then there is no paradox.
|
| [1] https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser
| zeroonetwothree wrote:
| If you allow hidden variables it's also easily resolved ;)
| ko27 wrote:
| Good thing we ruled out local hidden variables.
| https://en.wikipedia.org/wiki/Bell_test
| NoThisIsMe wrote:
| The _local_ part is important. We haven 't ruled out
| hidden variables. Bell himself preferred hidden variable
| interpretations.
| danielam wrote:
| A side note: Robert Koons at UT Austin has just published a book
| in which he examines the lesser known Aristotelian interpretation
| of QM. Here's a short review of the book[0] (the book is quite
| cheap for the genre) and a lecture Koons gave last year.
|
| [0] https://www.thepublicdiscourse.com/2023/01/86512/
|
| [1] https://youtu.be/Mf-iVHgIz3E
| BadThink6655321 wrote:
| Edward Feser published a review of Koon's book ([0], [1]). I
| was struck by the number of times Feser argued that a "common
| sense" view of QM is the one that is "basically correct." Given
| the documented failures of common sense in mathematics and
| physics (see especially Feynman's comments in the first 15
| minutes of [2]), why should anyone think common sense is a
| reliable metric to how things are?
|
| [0] https://www.thepublicdiscourse.com/2023/01/86512/
|
| [1] https://edwardfeser.blogspot.com/2023/01/koons-on-
| aristotle-...
|
| [2]https://www.youtube.com/watch?v=41Jc75tQcB0
| zeroonetwothree wrote:
| Isn't the problem that everyone thinks a different
| interpretation is the "common sense" one?
| danielam wrote:
| The article you provide a link to is the review I linked to
| (and that article mentions that Heisenberg was partial to the
| hylomorphist view of QM).
|
| > Given the documented failures of common sense in
| mathematics and physics [...], why should anyone think common
| sense is a reliable metric to how things are?
|
| I think the most serious objection is that categorical
| dismissal of common sense is a form of skepticism, and as a
| consequence, you undermine the very claims you are appealing
| to. All science takes place within a context and that context
| is going to be common sense, ultimately; the alternative is
| some truncation or corruption of it. So you might as well own
| it and own it to the fullest. All skepticisms suffer from the
| same problem, namely, the strange belief that you can know
| something while undermining the very conditions possibility
| of knowing it.
|
| Note that by "common sense", we mostly mean that we take the
| human apprehension of the world as _basically accurate_ ,
| even if it is fuzzy around the edges or needs correction or
| refinement [0]. So at the very least, I think that the
| presumption is in favor of common sense. Your question does
| not provide a reason for doubting common sense categorically
| or even rejecting common sense interpretations of QM. It is a
| better idea to engage with the proposed interpretation, to
| understand it, and make specific criticisms instead.
|
| [0] https://www.firstthings.com/web-
| exclusives/2012/10/aristotle...
| breuleux wrote:
| > All skepticisms suffer from the same problem, namely, the
| strange belief that you can know something while
| undermining the very conditions possibility of knowing it.
|
| I think these conditions are overstated. The human brain is
| a paraconsistent reasoning machine: it is made to be robust
| to inconsistency and contradiction. I think it is obvious
| that there exist logical contradictions in the belief
| systems of every human being, and it is equally obvious
| that we can reason productively in spite of them, so is it
| really that big of a deal?
|
| It is not clear to me that we ought to believe something
| merely to avoid an inconsistency. If our common sense is
| indeed error-ridden, I would argue that it is ultimately
| better to accept the skeptic position and let our brains
| deal with the internal inconsistency than to accept a
| falsehood merely to preserve consistency.
| TheOtherHobbes wrote:
| No, common sense means we're using metaphors from a limited
| range of Earth-based everyday experience on a fairly cold
| planet where everything moves slowly to make predictions
| about physical phenomena.
|
| In science, common sense has been wrong so consistently its
| wrongness is practically empirical.
|
| QM, relativity, thermodynamics, gravity, astrophysics,
| electromagnetism, and math itself are profoundly and
| consistently unintuitive - to the extent that if someone
| starts a claim about reality with "Well, obviously..." you
| can pretty much bet they're wrong.
| guerrilla wrote:
| > All skepticisms suffer from the same problem, namely, the
| strange belief that you can know something while
| undermining the very conditions possibility of knowing it.
|
| This is incorrect. That's now how Pyrrhonism works. They
| have the same critiques of other skeptics.
| Vox_Leone wrote:
| It would seem to me that the sheer amount of observation on the
| macro scales has the effect of freezing the quantum observables
| in space and time, giving rise to the common, agreed-upon,
| reality. Seems like a solution to a problem.
|
| [edited for spelling errors]
| russdill wrote:
| The concept for this is called decoherence
| danbruc wrote:
| _[...] freezing the quantum observables in space and time
| [...]_ also sounds like the quantum Zeno effect [1] which is
| kind of the opposite of decoherence [2].
|
| [1] https://en.wikipedia.org/wiki/Quantum_Zeno_effect
|
| [2] https://en.wikipedia.org/wiki/Quantum_decoherence
| chriswarbo wrote:
| That's usually referred to as 'decoherence'
| https://en.wikipedia.org/wiki/Quantum_decoherence#In_interpr...
|
| (Observation can also literally freeze the state of a system,
| via the Quantum Zeno Effect
| https://en.wikipedia.org/wiki/Quantum_Zeno_effect but that's
| based on observing the same system over and over again, not
| different systems interacting)
| UseofWeapons1 wrote:
| Fascinating. The summary:
|
| "On the one hand, according to the (generalized) standard
| canonical interpretation, the arrival distribution is considered
| as a generalized observable, which is described by a positive-
| operator-valued measure (POVM), satisfying some required
| symmetries [10, 11, 30, 31]. On the other hand, in the realistic-
| trajectory-based formulations of quantum theory, such as the
| Bohmian mechanics [32], Nelson stochastic mechanics [33], and
| many interacting worlds interpretation [34], the arrival time
| distribution could be obtained from particles trajectories [7,
| 18, 35, 36]."
|
| I'd be interested to hear a definition of each of those
| interpretations.
| User23 wrote:
| Bohm is the pilot-wave theory[1].
|
| [1] https://en.wikipedia.org/wiki/Pilot_wave_theory
| [deleted]
| ko27 wrote:
| If this paper is correct and we can experimentally verify
| different QM interpretations, then this is really
| groundbreaking stuff. I wonder why this news isn't everywhere.
| fredgrott wrote:
| That is about like saying photons can display quantum
| interpretations given that photons are the entities that interact
| with double slits in the first place.
|
| Or event to get more eccentric, your ocular lobes can interpret
| quantum because they receive photon interactions with the rod
| cells.
|
| Just pointing out the obvious problems with tongue-in-cheek.
| gumby wrote:
| The first author named on the paper is...interesting. A literal
| _ghost_ writer.
| eternalban wrote:
| Yes, "interesting". A cry for help from Sharif University,
| perhaps. Ayatollah Ali Akbar Rafsanjani gave up the _ghost_
| rather 'unexpectedly'. Prior to his sudden removal from the
| scene he had made remarks regarding Japan, Germany, and their
| ultimate relationship with USA. He was an eminently pragmatic
| ideologue. This internal contradiction clearly proved to have
| had adverse health consequences.
|
| https://www.theguardian.com/world/2018/jan/09/iran-reopens-i...
|
| _" Today, you can see that Germany and Japan have the
| strongest economies in the world. These same two countries were
| prohibited from having military forces after the Second World
| War. When a country is at war, it spends so much money on its
| military. With no military spending, these countries could use
| that extra money on science and production and were able to
| create a science-based economy for themselves. As a result,
| they are no longer fragile. The door has been opened to a
| similar process in Iran."_
|
| https://www.al-monitor.com/originals/2016/09/ayatollah-hashe...
|
| Yes, you are correct to read that and understand the Ayatollah
| Rafsanjani was explaining the benefits for Islamic Republic to
| throw in the towel and join the ranks of former enemies now
| prosperous allies of US: Germany and Japan.
|
| https://www.newyorker.com/news/news-desk/rafsanjani-irans-wi...
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