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Researchers At Brown University Shattered a Quantum Wave Function 150

Jason Koebler writes: A team of physicists based at Brown University has succeeded in shattering a quantum wave function. That near-mythical representation of indeterminate reality, in which an unmeasured particle is able to occupy many states simultaneously, can be dissected into many parts. This dissection, which is described this week in the Journal of Low Temperature Physics, has the potential to turn how we view the quantum world on its head. Specifically, they found it's possible to take a wave function and isolate it into different parts. So, if our electron has some probability of being in position (x1,y1,z1) and another probability of being in position (x2,y2,z2), those two probabilities can be isolated from each other, cordoned off like quantum crime scenes.
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Researchers At Brown University Shattered a Quantum Wave Function

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  • by Anonymous Coward

    Umm.... I still don't get what the article is trying to articulate. Can someone explain? All I was able to grasp is that the particles can be in multiple states of x1,y1,z1 and x2,y2,z2. But what's the point?

    • by Anonymous Coward

      I'm also not sure what's the implication here. Saying "dissected into many parts" and "isolated from each other" sounds like particle duplication to me.

      • Re:umm.. what? (Score:4, Informative)

        by duck_rifted ( 3480715 ) on Wednesday October 29, 2014 @01:43PM (#48262547)
        I took the question to be more a layperson's request for explanation. I don't think they meant to get that technical, though I could be wrong.

        This isn't particle duplication. States are marked, and then the particle is observed in one state. But then the other states can be observed as well -- there just won't be an electron at any of those places except the one where it is observed.

        You're confused because you're mixing up the states of a particle with the particle itself. If your wave function describes a distribution of positions, then each position continues to exist after the wave function is collapsed by observation.
      • The only discrete piece of information that I got out of the article that seems unambiguous is: it appears that for a long time detectors were detecting certain properties of an electron, rather than the electron as a whole, but nobody knew what that meant.
    • Re:umm.. what? (Score:5, Interesting)

      by halivar ( 535827 ) <bfelger&gmail,com> on Wednesday October 29, 2014 @01:17PM (#48262297)

      Well, I'm hardly a physicist, but it reads like they cut Schrodinger's box in half, pulled a dead kitty out of one and a live kitty out of the other. Is this incorrect?

      • by Anonymous Coward

        Essentially what I got. They can, given a probability, make a prediction based upon that probability - like what was once a black box now appears to be a branch in formulae.

      • Re:umm.. what? (Score:4, Interesting)

        by mspohr ( 589790 ) on Wednesday October 29, 2014 @01:30PM (#48262407)

        ... with a certain probability of kitty in each...
        Still can't figure out if the cat is alive or dead since's it's both.

        • It's not either until you look. Measurement is what causes the event to resolve itself.

           

          • "Measurement is what causes the event to resolve itself."

            So it really isn't definite until measured, or interacted with?

            How close is this to stating it doesn't exist unless it is interacted with?

        • Still can't figure out if the cat is alive or dead since's it's both.*

          *maybe

      • Re: (Score:2, Informative)

        by Anonymous Coward

        This is incorrect. The kitty analogy doesn't really work well here because the idea of the box itself is what is in question. It would be closer to finding that what you thought was a box with one kitty was really a box with kitty pieces that can be spread out and opened and all still be "alive" (or dead).

      • by Anonymous Coward

        That can't be right. That would mean that two particles were created from 1. Unless it takes more energy to do this than the equivalent energy of the doubled particle has, wouldn't this be a net gain in energy in the system?

      • Well, I'm hardly a physicist, but it reads like they cut Schrodinger's box in half, pulled a dead kitty out of one and a live kitty out of the other. Is this incorrect?

        almost...

        Ever seen the movie Cube? Like that.

        • Well, I'm hardly a physicist, but it reads like they cut Schrodinger's box in half, pulled a dead kitty out of one and a live kitty out of the other. Is this incorrect?

          almost...

          "Ever seen the movie Cube? Like that."

          But less than Cube 2: Hypercube

      • will we be able to commun -

        q439542-dir34r0q=

        -- civilization disconnected, return to base

      • by Kanasta ( 70274 )

        You can't get 2 kitties out of one. They cut Schrodinger's box in half, and pulled /half/ a dead kitty out of one and /half/ a live kitty out of the other.

    • Re:umm.. what? (Score:5, Informative)

      by duck_rifted ( 3480715 ) on Wednesday October 29, 2014 @01:37PM (#48262491)
      I can explain briefly. Since I don't know your background, I'll break this up into sections. Skip what you know.

      Scale

      Depending on the lengths of space involved with a topic of study in Physics, one of three schools of thought will be used. At the macro scale, the lengths that we experience day to day, Newtonian mechanics are usually good enough. At very large scales appropriate for studying stars, planets, and so on, General Relativity comes into play. At very small length scales appropriate for studying atoms and their constituent particles, Quantum Mechanics is used. There are far more fields in Physics, but these three provide the broadest toolset in these terms.

      Superposition

      The world as we experience it has some fairly intuitive rules, like cause and effect. We call that determinism; that if we know the initial state of a system and the rules that it follows then we can predict what state it will end up in. You know what will happen if you life your mouse and let go: it will fall to the surface you lifted it from. In Quantum Mechanics, determinism does not apply.

      One of the things required for determinism to work is that one set of initial conditions produces one outcome under the rules that govern how the system proceeds in time. The dropped mouse falls back to the surface beneath it. In Quantum Mechanics, there is no "one outcome", but instead there are many. Let's call these outcomes "states," because this applies to the initial conditions as well. When an observation is made, only one state is found, and the wave function describes the probabilities of finding each related state. Until the observation is made, every state exists or is happening simultaneously. We call that a "superposition" of states.

      Wave Summations

      One of the mathematical tricks used to solve for a wave function takes into consideration several possible waves and sums them. Now, this gets fairly complicated and it's well beyond the scope of an Internet forum post to explain it fully. Suffice to say that we call each wave summed to get the end wave function a "wave packet". That math is at work around you all the time; it's used to turn the analog radio signals used for broadcasts into square waves for digital broadcasts, for example. The researchers discussed in this article are not breaking down wave functions into wave packets, but I explain this because I want to impress upon readers that wave functions describe multiple states.

      Finally, this article...

      The researchers have found a way to isolate states in the superposition to observe them individually, which is interesting for many reasons. You may have heard of the double slit experiment, which is a good analogy for this. When particles are observed before passing through the slit, they appear as particles with determinate positions (wave function collapse) but when they're not observed, they appear as interference patterns between waves (superposition). Using that experiment purely as an analogy, these researchers have found a way to observe the particles that form the interference patterns so that each can be studied individually.
      • Re:umm.. what? (Score:4, Informative)

        by UnknownSoldier ( 67820 ) on Wednesday October 29, 2014 @01:47PM (#48262569)

        That's a pretty good summary !

        Some really good videos ...

        Quantum Physics And How We Affect Reality!
        https://www.youtube.com/watch?... [youtube.com]

        The Quantum Conspiracy: What Popularizers of QM Don't Want You to Know
        https://www.youtube.com/watch?... [youtube.com]

        Hint: There is no conspiracy -- just a Google Talk about entanglement and wave collapse

        • I watched that Quantum Conspiracy one. That guys made the same mistake a lot of "smart but not a physicist" types make. Yes, you can explain many quantum effects classically... the double slit experiment is easily explainable using just optics. But that does not invalidate Quantum Mechanics or provide answers to a myriad of other problems that it addresses that are not easily explained without expensive lab equipment and a graphing calculator.

          He did explain several things very well though. He's clever, but

      • This sounds like a way to detect many of the possible positions of a particle at the same time. Could this be useful for quantum computing?
      • "Using that experiment purely as an analogy, these researchers have found a way to observe the particles that form the interference patterns so that each can be studied individually."

        what happens after being studied individually..can they still be collapsed into each of the various states?

        • Re:umm.. what? (Score:5, Informative)

          by duck_rifted ( 3480715 ) on Wednesday October 29, 2014 @03:02PM (#48263393)
          The particle (an electron in their experiment) still collapses to only one of those states. I have an analogy that may help.

          Suppose that you have a groundhog to catch, and this groundhog has dug a network of tunnels around your property. Every night, he comes out and eats your veggies, and you know that he will come out of only one of his holes. You know as well that he tends to favor some holes more than others. So, you are advised to place a trap at the most likely hole and keep trying until you catch him.

          Then, a scientist from Brown University calls you up, and says, "Wait! All of those holes are important! Place one trap at every hole." That's what you do, and instead of waiting however many nights it could take to catch the groundhog by chance, you catch him on the first night. Now you have a groundhog in one trap, and you have all the other traps marking the holes. That makes it easy to deal with the groundhog while keeping the holes marked for landscapers to come.

          So, you can study the one groundhog and you can study all the holes, but the groundhog still only got caught in the one trap.

          The electron is still only observed in one state because there's only one electron and the wave function still collapses to that one state upon observation. But every state it might have collapsed to is marked, and those states can be observed and studied even though they don't have electrons.
      • Maybe you'd be a good person to ask -- the collapse is the end of superposition, but where does it "begin"? We say that an electron passes through the double slit which sounds like it is a definitive single particle/wave, but I'm guessing that electron itself is one possible state of the part of the quantum system ie. of the cathode that emitted the electron or not, the cathode itself being a part of the larger system and so on. So the electron that may or may not have been emitted from the cathode may or m

        • Particles are waves until they are observed. They only appear to be particles when they are observed at a single place and time.

          Think of two ends of a rope being held by different people. One end of the rope can be lifted and lowered to send a soliton - a kind of wave with only one bump - to the other end of the rope. Suppose that you aim to describe the position of the bump.

          Observing the entire rope, it's a wave. But if you measure the position of the bump itself then your measurement only has an
          • Thanks. "The bump is the rope; the wave and bump are one" is a good way to put it. I found a paper by Art Hobson of UARK claiming that "There are no particles, there are only fields" (http://arxiv.org/ftp/arxiv/papers/1204/1204.4616.pdf), this sounds similar. So phenomena appear to us as particles, and we model those phenomena as waves to predict how/where/when they will manifest to us. Seen that way, I think the double slit experiment isn't any more mysterious than any "ordinary" electron behavior, but it'

      • Excellent post, but one thing bothers me.

        In Quantum Mechanics, determinism does not apply.

        Isn't that begging the question? I'm not a physicist, but my understanding is that the question of determinism is a matter of interpretation. (Quantum mechanics can be understood to be deterministic.) Isn't that the question they are poking at here?

        • It is true that many people have spent a long time trying to make Quantum Mechanics deterministic, and in some cases there has been limited success (such as in this story). But the particle is ultimately still in a superstate until the wave function collapses due to observation. Usually we call such systems or math "semi-classical", that attempt to bring determinism to Quantum Mechanics. There are many great attempts out there, and all (or nearly all) have their specific applications and usefulness. How
    • by STRICQ ( 634164 )

      It's Geordi's Heisenberg Compensator.

    • IAMA physicist, but not a very good one and this isn't my field.

      From what I gather, they got liquid helium to react to the wavefunction of an electron without reacting to the electron itself. In other words, an electron approached the surface of a vat of liquid helium, the helium reacted (by forming bubbles), but the electron continued and eventually reacted somewhere else.

      If true, this is really, deeply, weird. The wavefunction is supposed to be just a mathematical model of where the electron should be.

  • by Anonymous Coward

    Which one is the right one ?

  • by pla ( 258480 ) on Wednesday October 29, 2014 @01:17PM (#48262295) Journal
    Brown?

    Brown???

    Sorry, I knew too many Brownies back in my uni days. More likely, they just forgot about "bigger bottom, better borrow" and broke the wave function the old fashioned way. ;)

    / I could also have gone with "paid daddy to break it for them", but took the high ground... this time!
  • One of these days humanity will get the Galactic Darwin Award.

    "Here at the LHC, News 9 is about to witness the first ever batch of artificial mini black holes. Here comes the first one now...oh shi~ ^& [NO CARRIER]

    • Comment removed (Score:4, Informative)

      by account_deleted ( 4530225 ) on Wednesday October 29, 2014 @01:26PM (#48262367)
      Comment removed based on user account deletion
      • Comment removed based on user account deletion
      • by Tablizer ( 95088 )

        Yes, but there may be something about the atmosphere or environment up there that mitigates the effects. I don't think it's likely, but the probability is greater than zero.

        Ideally, we'd do such experiments on the moon or Mars instead of Earth.

    • Or someday one of us is gonna experiment with a device to collapse wave functions at will, accidentally reverse the switch and turn planet earth into one big wave function. Then later an alien astronomer will look at earth through a telescope and find a jungle planet full of sentient cats playing ball with their pet hominids.

  • by nxcho ( 754392 ) on Wednesday October 29, 2014 @01:21PM (#48262323)
    "...cordoned off like quantum crime scenes." I like creative usage of metaphors in science.
  • IANAP but haven't they just constrained the distribution of probability somehow? I mean how it's distributed in space. Don't we do this every morning when we put our pants on?
    • IANAP

      You're in good company. None of us here is portabella.

    • by Anonymous Coward

      IANAP but haven't they just constrained the distribution of probability somehow? I mean how it's distributed in space. Don't we do this every morning when we put our pants on?

      Some of us don't wear pants. Ever. Perhaps it's to avoid constraining probabilities...

      • I think you'll find that the lack of pants constrains probabilities even more severely...

        The real trick is to find a pair of Schroedinger Pants so that you can leave the house without anyone knowing whether you're wearing them or not, yourself included. Not many stores keep them in stock though - they play hell with inventory management.

      • by Anonymous Coward

        What we are singing~
        is take off your pants~

    • by Tablizer ( 95088 )

      Don't we do this every morning when we put our pants on?

      We're supposed to wear pants? No wonder I just got a pay cut.

    • They constrained the distribution of the electron's probability without affecting the electron. That's very, very weird.

  • by gstoddart ( 321705 ) on Wednesday October 29, 2014 @01:26PM (#48262369) Homepage

    So, does this or does this not give us the basis for the Heisenberg compensators?

    Might quantum stuff me less random and unknowable than we've been told?

    And, yes, I don't understand Quantum anything, other than knowing it makes your whites whiter, and has a smooth minty taste.

    • Heisenberg compensators? Are those parts of the flux capacitor or parts of Mr. Fusion?

      • Heisenberg compensators? Are those parts of the flux capacitor or parts of Mr. Fusion?

        Yes. Possibly no.

        It depends. I may know more later.

      • Actually, they're an integral part of Star Trek's transporters. When someone asked Mike Okudo how they worked, he replied, "They work just fine, thank you."

  • by account_deleted ( 4530225 ) on Wednesday October 29, 2014 @01:39PM (#48262505)
    Comment removed based on user account deletion
  • Actual abstract (Score:5, Informative)

    by blueg3 ( 192743 ) on Wednesday October 29, 2014 @01:40PM (#48262509)

    "An electron in liquid helium forces open a cavity referred as an electron bubble. These objects have been studied in many past experiments. It has been discovered that under certain conditions other negatively charged objects can be produced but the nature of these “exotic ions” is not understood. We have made a series of experiments to measure the mobility of these objects, and have detected at least 18 ions with different mobility. We also find strong evidence that in addition to these objects there are ions present which have a continuous distribution of mobility. We then describe experiments in which we attempt to produce exotic ions by optically exciting an electron bubble to a higher energy quantum state. To within the sensitivity of the experiment, we have not been able to detect any exotic ions produced as a result of this process. We discuss three possible explanations for the exotic ions, namely impurities, negative helium ions, and fission of the electron wave function. Each of these explanations has difficulties but as far as we can see, of the three, fission is the only plausible explanation of the results which have been obtained."

    Research group website [brown.edu]
    Non-paywalled copy of paper [brown.edu]

    TLDR: This research group studies exotic electron effects in superfluid helium. They see a particular effect that is not currently explained. There are a few possible explanations, and they argue that a particular one is probably true.

    Inaccurate "news" articles ensue.

    (The physics is subtle enough that, despite reading the abstract and bits of the paper, I would not venture to try to summarize it. You can smell a mile away, though, that this article is poor understanding mixed with hyperbole. The specific flavor is, "Quantum Mechanics is Philosophical Magic".)

    • by Anonymous Coward

      The description sounds almost like an electron is composed of two things that may oscillate (probably need a better word) about each other.
      The helium bubbles seem to sometimes capture the two things separately and sometimes together.

      Previously folks expecting the latter and seeing the former called it an experimental error because it did not match their understanding of what an electron is.
      These folks are saying that the former is a real aspect of the thing we know as an electron.
      What sort of an aspect is a

    • The specific flavor is, "Quantum Mechanics is Philosophical Magic".

      The simpler explanation that cannot be denied?

      Turtles...

    • Tentative summary (Score:5, Informative)

      by Immerman ( 2627577 ) on Wednesday October 29, 2014 @02:58PM (#48263353)

      I'll venture a summary of their experiment and hypothesis, though I didn't read the paper itself and I won't swear that it's accurate:

      When a single electron enters a container of helium superfluid it repels the surrounding atoms, creating a bubble of definite size, which proceeds to slowly sink to the detector at the bottom at a determinate rate based on it's size - the larger the bubble, the slower it sinks. Before those electron-bubbles reach the detector; however, it is apparently detecting additional, unexplained charges traveling at at least 18 discrete speeds and, more rarely, charges that seem to travel on a continuous spectrum of speeds. They believe it to be unlikely that there are a sufficient range of impurities in the fluid to explain such a large number of speeds, and hence an alternate explanation should be sought.

      Their hypothesis is that these additional charges are in fact smaller bubbles formed by electron wave functions being partially reflected at the liquid's surface: on impact an electron may either enter the fluid, or bounce off. Or, thanks to quantum superposition, it may do both simultaneously with varying levels of probability. In the latter case the partial wavefunction that did penetrate the fluid surface could be expected to create smaller (faster) bubbles in a variety of sizes - some of the electron probability is not within the bubble, and so the repulsion effect is lower and the bubble correspondingly smaller and faster moving.

      As I understand it the implication is that simply interacting with the helium is insufficient "measurement" to collapse the wavefunction, instead it gets to maintain a partial presence until such time as it interacts with the detector, which measures it's presence with sufficient definitiveness that the electron must then be wholly present or absent. This would be a revolutionary finding as it would be the first time that a superposition of states has been detected to measurably impact the interaction of a particle with its environment - in all previous QM experiments when a wavefunction collapsed and a single particle was detected, its position and velocity were consistent with the history of a single classical particle traveling along the path that ended in detection, and superposition could only be detected in the statistical distribution of detections, such as the interference patterns of a two-slit experiment.

      If correct, this could be a major step forward in determining what exactly constitutes a "measurement" for the purposes of collapsing a quantum wavefunction, a question which has thus far gone almost completely unanswered and spans the complete range from the vague "interaction with the macroscopic world" to the quasi-mystical "observed by a conscious mind"

      • by jfengel ( 409917 )

        Thanks. No mod points today, but I appreciate somebody attempting to extract information from this rather than just apply quantum juju. #ifuckinghatesciencewriters

      • by AdamHaun ( 43173 )

        Many thanks to you and blueg3 for providing a better summary. These terrible analogies for quantum mechanics are always more confusing than helpful.

      • by radtea ( 464814 )

        This would be a revolutionary finding as it would be the first time that a superposition of states has been detected to measurably impact the interaction of a particle with its environment - in all previous QM experiments when a wavefunction collapsed and a single particle was detected, its position and velocity were consistent with the history of a single classical particle traveling along the path that ended in detection

        I don't see that this experiment is any different from a photon reflecting between parallel partially-silvered mirrors. You see a range of arrival times at the detector, despite the wavefunction being "fragmented" by multiple reflections.

        So this won't do anything to advance measurement theory. It is an interesting example because of the exotic circumstances. Your description is extremely good and quite plausible, although I haven't read the paper either.

        • I don't see that this experiment is any different from a photon reflecting between parallel partially-silvered mirrors. You see a range of arrival times at the detector, despite the wavefunction being "fragmented" by multiple reflections.

          I only got a chance to scan the paper, but my impression is this. The difference is that the split electron wavefunction is creating a bubble in the liquid helium. Splitting a quantum wavefunction is rather boring: it's pretty easy, all you need is a finite barrier to produce tunneling, or a double-slit to produce separate paths, or a bunch of other ways. What this experiment does, though (if they're correct about the cause) is show that the split wavefunction actually affects the matter through which it tr

        • I think the point is that in your parallel mirror example, for any given *single* photon detected, you can "reverse engineer" a path wherein a single classical-physics particle-photon bounced between the mirrors multiple times before finally making it through to the detector. On each bounce you get a fragmented wave function, but both fragments continue to behave as though they were "whole photons" until the wave-function collapses. For a population you get a spread of arrival times (in discrete "time to

      • Thank you for a superb, comprehensible summary.
      • That's pretty much the way I understand it. This is exciting enough so that I am going to read through the full published article. If true (can't wait for others to try to reproduce it), then one of the stranger things implied is that while in a superposition of different positions, other particles feel the electron's field not just in proportion to 1/r^2 but also in proportion to its probability amplitude of being in that particular position at all. It also seems to provide a way around the "decoherence
      • by ODBOL ( 197239 )
        Thanks for the excellent summary of what the two articles seem to say. If I were competent with the Slashdot interface, I would mod this up for "Informative," but I can't find the right buttons. The puzzle, which I hope someone with real understanding of quantum theory will explain (I will dig into the original paper, but not with great optimism for my understanding):
        • It seems that when a single electron hits this blob of helium, it has many possible paths through the helium in bubbles, each with a differe
        • Hmm, that's not how I read it (though I still haven't gotten around to reading the paper, so please let me know if I'm going off-track). It sounds like the bubbles are *created* by the electrons as they enter the fluid - no electrons equals no electrostatic repulsion field repelling the surrounding helium equals no bubble. And it's not that the paths through the liquid have different wavefunctions, it's that fractional wavefunctions created when an electron is partially reflected from the liquid's surface

  • Where does the math meet real-world engineering?
  • Researchers At Brown University Shattered a Quantum Wave Function

    Initial reports of recent events don't usually go for the past tense. It looks a bit weird.

    So, if our electron has some probability of being in position (x1,y1,z1) and another probability of being in position (x2,y2,z2), those two probabilities can be isolated from each other, cordoned off like quantum crime scenes.

    Yeeaaah... I'm not sure that analogy is as helpful as the author hoped.

  • Carver Mead (national medal of technology winner, father of chip design, founder of several billion$ physics based companies) has a simpler, more realistic model of an electron: it is not a point-particle that somehow orbits a nucleus, nor is it a magical probability cloud that materializes when observed; rather a bound electron is a 2D surface wave of EM energy in the shape of a shell surrounding a nucleus. The shape of the shell ("orbital") depends on the energy of the wave interacting with other bound el

  • “No one is sure what actually constitutes a measurement. Perhaps physicists can agree that someone with a Ph.D. wearing a white coat sitting in the lab of a famous university can make measurements. But what about somebody who really isn’t sure what they are doing? Is consciousness required? We don’t really know.”

    If so, you can just about guarantee that we're living in a simulation.

  • by Anonymous Coward

    I just hope they have a spare!

    It would be bad to explain to your teacher "I couldn't finish my report because I broke my only quantum wave function!!!"

  • by Anonymous Coward

    So, if our electron has some probability of being in position (x1,y1,z1) and another probability of being in position (x2,y2,z2), those two probabilities can be isolated from each other, cordoned off like quantum crime scenes.

    Oh, like crime scenes. That really clears things up! Thanks to the power of analogy, I finally understand quantum hoo-hah as it applies to wave functions, much like I know that space-time is a rubber sheet, superstring theory is about tiny strings, and the multiverse is a giant loaf of

  • Emmet Brown, is that you?

Understanding is always the understanding of a smaller problem in relation to a bigger problem. -- P.D. Ouspensky

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