back to article Schrödinger's cat explained with neutrinos

Physicists have found that neutrinos keep their quantum weirdness over the longest distance that quantum mechanics has been tested to date. Superposition is a fundamental theory in quantum mechanics. The idea that particles can exist simultaneously in many different states was famously compared to a thought experiment devised …

  1. Stevie

    Bah!

    Yesyesyes, the cat, good.

    Now explain Schrodinger's haircut. What, did he lose a bet pr something?

  2. Baldy50

    No cats were harmed.

    Were any neutered?

  3. This post has been deleted by its author

    1. Anonymous Coward
      Anonymous Coward

      Re: "hunt for these particles in vats of chlorine liquid"

      "Anyway, your dry-cleaning fluid has chlorine-37 atoms in it, and occasionally a neutrino will interact with one and turn it into an Argon-37 atom which can be detected, as it's radioactive."

      So if I take a really, really big duvet to be dry cleaned in a sufficiently big cleaner, there's a risk of radioactivity? Can't be too careful.

  4. Derek Jones

    Neutrons change flavor but Leggett cannot contain fewer gs

    In my universe Legett-Garg contains 4 instances of the letter g.

    1. frank ly

      Re: Neutrons change flavor but Leggett cannot contain fewer gs

      Are they all the same flavour?

    2. Arthur the cat Silver badge
      Boffin

      Re: Neutrons change flavor but Leggett cannot contain fewer gs

      In my universe Legett-Garg contains 4 instances of the letter g.

      I presume one is a sterile g?

    3. Tromos

      Re: Neutrons change flavor but Leggett cannot contain fewer gs

      Simple. The first two 'g's are in a state of superposition.

  5. magickmark
    Mushroom

    Quantum theory and spatial dilution.

    This is from a mock paper by a guy called Michael H.F. Wilkinson. Sadly the link that I found it on seems to no longer work :(

    The famous thought experiment of Erwin Schrödinger describes how according to quantum mechanics a cat may be in an indeterminate state between living and dead, until a conscious observation is made. Likewise, Reitz (6) has shown that the location of a cat inside or outside a garage is unspecified until the creature is observed. This phenomenon explains the curious "tunneling" of electrons and even entire cats (6) through a region of space in which they cannot exist. If we take the case of a homeopathic dilution of a single molecule over N flasks of solvent, quantum mechanics tells us that the molecule is not located in a particular flask until a conscious observation is made. In quantum parlance, the "wave function" of the particle is said to "collapse" into a specific state (or flask) due to the act of observing. Incidentally, this is why cats resent people staring at them: the constant collapse of their wave function is a strain on their delicate senses.

    1. magickmark

      Re: Quantum theory and spatial dilution.

      Just found the link http://www.cs.rug.nl/~michael/qthair.pdf

    2. m0rt

      Re: Quantum theory and spatial dilution.

      Isn't Michael H.F. Wilkinson a commentard on here, too?

      1. magickmark

        Re: Quantum theory and spatial dilution.

        Yes he is!

      2. DropBear

        Re: Quantum theory and spatial dilution.

        "Isn't Michael H.F. Wilkinson a commentard on here, too?"

        Possibly, but only after he's observed...

  6. Red Bren

    Wrong

    "A cat in a sealed box exposed to a vial of poison was both dead and alive at the same time, until somebody opened the box and checked, Schrödinger said."

    Schrödinger said no such thing. Expose the cat to the poison and it will be dead. His thought experiment relies on the exposure being triggered by a quantum event that may or may not have happened, not the fact you put a cat in a box.

    1. Terry 6 Silver badge

      Re: Wrong

      Well yes, in the thought experiment the lethal act would be reliant on the quantum event triggering the release of the poison. Until the quantum event is observed to have/have not happened the release of the poison also has/hasn't happened. So the hapless moggy would also be dead/alive. But would probably have a nasty headache through trying to think about this.

  7. Pascal Monett Silver badge
    Coat

    "And even then, we can't stop using quantum mechanics"

    Translation : even wizards can get addicted.

    And you have to be a wizard to even begin understanding this field.

    I bow to our new superposed neutrino-wielding overlords.

  8. Anonymous Coward
    Anonymous Coward

    What's distance got to do with it?

    Distance in the quantum world is not the same as distance in our perception.

    1. asdf

      Re: What's distance got to do with it?

      Especially to a particle that can go through a light year long block of lead unscathed.

      1. Anonymous Coward
        Happy

        Re: What's distance got to do with it?

        and where do they get these light-year long blocks of lead, Tesco's?

    2. Anonymous Coward
      Anonymous Coward

      Re: What's distance got to do with it?

      Distance in this case is a proxy for time, or around 0.0025 seconds when the neutrinos were in a superposition state.

  9. Anonymous Coward
    Anonymous Coward

    Schrödinger

    Schrödinger's cat had 4.5 lives... statistically speaking.

    1. AIBailey

      Re: Schrödinger

      So the cat was already at a significant disadvantage compared to any non-Schrödinger cat.

      Presumably it got its revenge by shitting in his flowerbeds as much as possible.

    2. Spudley

      Re: Schrödinger

      > Schrödinger's cat had 4.5 lives... statistically speaking.

      And there was me thinking it had 18 half-lives.

  10. wobbly1

    Schrödinger's glowing cat?

    My understanding was that the cat was in a box with a radioactive source, rather than poison. and hence the indeterminacy of the cats mortality.

    1. AIBailey

      Re: Schrödinger's glowing cat?

      I think it involved a cat in a box containing a vial of poison. A single radioactive atom with a 1 hour half life was connected to a device that would break the vial should the atom decay. After 1 hour, there's a 50/50 chance that the cat is dead or not (or indeed, dead and not).

      1. wobbly1

        Re: Schrödinger's glowing cat?

        cheers!

        1. AIBailey

          Re: Schrödinger's glowing cat?

          TBH, the full explanation always seems clumsy. A simple scenario of "a cat in a box, that may or may not be dead" becomes, when fully explained, like one of those radio commercials that ends with 20 seconds of rapidly garbled words ultimately claiming "terms and conditions apply"

      2. DropBear
        Trollface

        Re: Schrödinger's glowing cat?

        "50/50 chance that the cat is dead"

        Oh, it's much worse than that actually - even AFTER you open the box to find a motionless cat: is it dead or only pining for the fjords?!?

  11. adnim
    Paris Hilton

    Nothing is determined

    until it is observed. And even then, observers tend to observe what they want to observe.

    Apparently according to the Schroedinger wave equation, observation aka measurement collapses the wave function. Were every single one of these Neutrinos observed before being sent off to the distant detector?

    I love thinking about this stuff, counting sheep and writing code in my head at bedtime gets tedious.

    Paris, because I would never look to her for intellectual stimulation.

    1. AdamG57

      Re: Nothing is determined

      Um, no. Things may be determined at any point. We don't know what was determined until it is observed. And this is science, so the wishes of the observer cannot matter - this is not some subjective reality.

      Imagine the radioactive trigger also stops a stopwatch when it goes off - you will know when the cat died, if triggered. And if you leave the cat unobserved for say a week, the chance it is alive when observed (that is, the decay with a half life of an hour) is next to nothing 1/2 to the power of 168...

      The collapse of the wave function, mathematically - and I'm on thin ice here - has to do with the cancelling out of so called imaginary numbers so that a real measurement can be taken.

      The part that interests me as an applied set theorist is the notion of three possible states rather than a binary alive or dead. What would Codd say to this implied proof of the real existence of nulls?

      1. Anonymous Coward
        Anonymous Coward

        Re: Nothing is determined

        "applied set theorist is the notion of three possible states rather than a binary alive or dead."

        Not a set theorist but I think the suggestion is of an infinite number of states between .....

      2. willi0000000
        Joke

        Re: Nothing is determined

        almost . . .

        And if you leave the cat unobserved for say a week, the chance it is alive when observed (that is, the decay with a half life of an hour) is next to nothing 1/2 to the power of 168...

        . . . actually the cat is certainly dead . . . thirst gets it before starvation unless the poison does it first.

        [ icon because somebody always takes me too seriously ]

      3. Andy The Hat Silver badge

        Re: Nothing is determined

        Is that modification to the experiment introducing the measurement problem? The very act of measuring - or even intending to measure (this is horrible!) - the current state (in this case via a stopwatch) will in itself define the quantum state, the wave function will be collapsed and everything is hunky dory (or not if you're a poisoned cat!) and non-quantummy-wierd.

  12. You aint sin me, roit
    Coat

    Although the neutrinos left Illinois as one flavour

    Hold on a minute!

    "The researchers proved that in-between the journey, the neutrinos were suspended in a superposition state of all the flavours – and had no definite identity."

    So how do they know which flavour they were when they left Illinois?

    If you play Schrodinger's Cat you need to know the cat was alive when you put it in the box!

    1. Chemist

      Re: Although the neutrinos left Illinois as one flavour

      "So how do they know which flavour they were when they left Illinois?"

      The experiment produces mostly muon neutrinos. A detector at the experiment confirms this and the remainder are detected after traveling the ~740km to the main detector.

    2. Mark 85 Silver badge

      Re: Although the neutrinos left Illinois as one flavour

      At least they got out of Illinois and avoided Chicago completely,

      If inspection/detection changes the state, indeed what flavor were they when they left since we assume they were inspected/detected before they left....

      1. Anonymous Coward
        Anonymous Coward

        Re: Although the neutrinos left Illinois as one flavour

        The on-site inspection is a separate process, they aren't doing that to the ones before they travel to Minnesota. They confirm that the apparatus they're using produces mostly muon neutrinos by checking the output with the local detector. After they've confirmed that, they remove the local detector and the neutrinos are then free to travel all the way to Minnesota.

        The device can't start outputting a different type of neutrino depending on whether there's a local detector or not unless the universe is a whole lot stranger than even quantum mechanics says it is.

        1. You aint sin me, roit

          Re: Although the neutrinos left Illinois as one flavour

          "The researchers proved that in-between the journey, the neutrinos were suspended in a superposition state of all the flavours – and had no definite identity."

          So why did they have a definite identity when travelling to a local detector?

          Is there a limit to the space/time they travel that enables the superposition state to take effect?

          What does "produces mostly muon neutrinos" even mean if they have "no definite identity" unless your detector is in the right position?

          1. Anonymous Coward
            Anonymous Coward

            Re: Although the neutrinos left Illinois as one flavour

            "What does "produces mostly muon neutrinos" even mean if they have "no definite identity" unless your detector is in the right position?"

            This all old stuff - if you'd like to educate yourself there are plenty of on-line explanations.

    3. Anonymous Coward
      Anonymous Coward

      Re: Although the neutrinos left Illinois as one flavour

      maybe it was playing alive?

  13. James Loughner

    Observer

    You mean the cat is not an observer? The cat know if it is dead or alive. Your ignorance is not a factor

    1. Anonymous Coward
      Anonymous Coward

      Re: Observer

      The exact definition of "observer" is one of the mysteries about quantum mechanics we haven't quite figured out for sure yet...

  14. elDog

    Please aim some of these towards Cleveland

    We might be able to determine if the Trumpster and the Republican Disestablishment is real, or not.

  15. John Savard

    What Did Schrodinger Really Say?

    He didn't really say that the cat was neither dead or alive until the box was opened. He just noted that this was what the equations of quantum mechanics seemed to imply that this is what would happen - unless, of course, cats also counted as "observers". So he was simply trying to highlight a limitation of the equations of quantum mechanics: they did not indicate how, when quantum phenomena collide with the macroscopic world that seems to behave classically, quantum states are caused to collapse into eigenstates of observables - as far as the equations of quantum mechanics are concerned, the whole world should be in a mixed-up superposed state like the cat.

  16. Velv

    2012

    Has anyone updated Dara O'Briain on his 2012 sketch?

    (on a line in the movie 2012) " 'The neutrinos have mutated.' Now, for the non-nerds here: neutrinos are tiny, sub-atomic, really really almost massless particles, they're released in nuclear breakdowns, like in the sun, for example. Five hundred trillion of them pass through your bodies every second. They can't mutate. Their structure is fundamental to the structure of the universe. Right? They can't just change. He might as well have gone, 'The electrons are angry'."

  17. Anonymous Coward
    Anonymous Coward

    Observation of neutrinos

    The cat in the box can be both dead or alive until it is observed by the observer. Until observed, the cat is in a superposed state. The neutrinos can exist simultaneously as muons, electrons or tau neutrinos until observed, so three flavours existing together in a superposition state until observed by the observer. I sense the neutrino is also an observer of itself (like the cat, knowing it's either dead or alive). The unfolding observations by multiple detectors could be independent of the neutrino itself along it's journey. The neutrinos ability to change flavours "sneaky" is very interesting to me.

    I enjoyed reading this article!

    1. Adalat

      Re: Observation of neutrinos

      If you open the box a week later, it will be obvious that the cat didn't go dead just at the moment you opened the box. (Note: this is best left as a thought experiment.)

  18. Adalat

    Don't confuse the cat with the uncertainty

    Sub-atomic particles may be subject to quantum effects like superposed states, but the consequences do not inherit that uncertainty. Stuff happens, without anybody observing it. My uncertainty is my problem, not the cat's. The cat may be unhappy at being locked in this stupid box, or it may be dead, but it is not uncertain.

  19. Anonymous Coward
    Anonymous Coward

    But

    Are you certain about that?

    I mean some cats *like* being put in a box, it calms them down if injured and the animal shelter recommend this for injured animals anyway.

    Hint: helps if you put a heat pack in there too if it is cold.

    1. Adalat

      Re: But

      If the cat knew what else was in Schrodinger's box, yes I am sure it would be unhappy.

  20. John Savard

    Of Course

    I suppose that this discovery should not be too surprising. A quantum system can stay in a superposed state until it is observed... and something that interacts so weakly with matter as a neutrino can stay unobserved for a longer time.

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Other stories you might like

Biting the hand that feeds IT © 1998–2022