Physicists Claim They Solved Schrödinger's Cat Problem

[@SabineHossenfelder]

This video comes with a quiz which you can take here: quizwithit.com/start_thequiz/1734940317262x453348685399263200 You can also create your own quizzes (using AI) on my platform!

[@Thomas-gk42]

thanks for another funny quiz.

[@AstroGremlinAmerican]

Mathematicians rely on assumptions. So do normals.

[@tommiest3769]

Can you please do a video critiquing Sara Imari Walker’s new book “Life As No One Knows It”?

[@violetquinnlaw]

instead of the cat in a box i prefer the cat on the operating table if your a vet reviving a cat whos heart has stopped. is it alive or dead and if you restart its heart did you bring it back to life(if you consider the stopping of a heart to be the point of death) or was it never dead to begin with?

[@PissyKnish]

I heard you are a fallacy.

[@sciencealien622]

As the first author of the referenced paper, let me try to clarify some of the confusion here. What our paper aims to demonstrate is that decoherence is generic! The same (!) observables decohere for almost every (!) Hamiltonian and almost every (!) inital state. So, coming back to the video, while it is true that one can find a specific interaction with a specific environment that does not decohere the cat, that situation is extremely unlikely or atypical (I leave it to Sabine to explain in another video the notions of "atypical" or "generic", which have a precise mathematical meaning). Moreover (and that's perhaps the bigger novelty of the paper), we find that quantum interference effects ("coherences") are exponentially suppressed with the number of particles. For instance, for a poison-box-cat system with 10^25 atoms it happens in 1 out of 10^{10^25} experiments to see something weird (i.e., contrary to our classical expectation). And yes, all what we do is "just a numerical demonstration", but I guess to appreciate the scope of our paper it is necessary to know a bit about modern many-body physics using random matrix theory or, more precisely, the eigenstate thermalization hypothesis. Also that topic I leave for another video of Sabine. :) Merry Christmas and happy new year!

[@shashankdeshpande7787]

It was always intuitive to me that classical emergence is a likelihood concentration phenomenon. It was quite later that I discovered that this has not been shown. Congratulations, I think your work is indeed useful in this regard.

[@kamilZ2]

I am glad that normality is restored. Can you calculate the approximate maximum number of qubits of quantum computer, and guarantee that bigger will not work?

[@dantkwb]

'Moreover (and that's perhaps the bigger novelty of the paper), we find that quantum interference effects ("coherences") are exponentially suppressed with the number of particles. For instance, for a poison-box-cat system with 10^25 atoms it happens in 1 out of 10^{10^25} experiments to see something weird (i.e., contrary to our classical expectation).' This is pretty impressive! Can we assume that the in-coherences are equationable and related to the number of particles?

[@Shadow_B4nned]

Well no,. I can help here. It's very simple actually. The "cat" is never in multiple physical positions at the same time. You're just uncertain in which position the cat is actually in. Superposition is a probability wave function. Not a certainty wave function. IE the cat has a 30% chance of there being decayed particles and a 70% chance of not. The cat does not magically multiply, nor does a proliferation of multiverses manifest itself to accommodate the energy constraints of such a manifestation from a few decayed particles. That's like saying a multiverse is created when you turn on the microwave.. I'm afraid not.

[@richardchapman1592]

@@sciencealien622 eigenstate probabilities through randomising matrices giving them? Sounds like an interesting extension of linear equations. Will you use non linear expressions for your variable values to give some fine tuning at zero and infinite lengths or would that be another way of tweaking the model to fit the data. There could be eigan values amongst the randomisations of variables that fit identifiable functions. Fingers crossed.

[@ricardolutzkysaute8483]

In the Schrodinger cat story, I have two questions: 1. If the nucleous is in a superposition state, it decayed AND not decayed, so it also decayed. Since it decayed, it would trigger the apparatus and the cat would be dead. Isn't it right? 2. If there is a detector and the apparatus depends on a detector to kill the cat, the detector would collapse the wave function. So, the superposition would be terminated by the detector and the nucleus would be revealed either to have decayed or not. So the cat would be either dead or alive, and not in a superposition state. Isn´t it right?

[@benriggs3108]

that cat was put in that box 90-odd years ago, it's dead..

[@SuatUstel]

Cat was pregnant

[@KenLieck]

Hence it is an "age-old" problem.

[@JZsBFF]

What if time behaves differently once we stop observing the cat?

[@ComeCleanAmerica]

How many lives does a cat have?

[@syntaxusdogmata3333]

@@JZsBFF Interesting posit... time, like cats, behaves differently when unobserved. Therefore time IS a cat!

[@jameswithers2334]

"...what's wrong with it?" "I'll tell you what's wrong with it! It's dead! That's what's wrong with it!" "No, no, it's resting, look!" "I know a dead cat when I see one, and I'm looking at one right now!..."

[@squeakeththewheel]

Jesus rose from the dead, right?

[@pietpaaltjes7419]

I think you mistook a parrot for a cat 🤣

[@tarquinbiscuit-barrel5871]

@@pietpaaltjes7419 NO NO it's not a cat, it's a Norwegian Blue!

[@doubledee9675]

Within a couple of days, you will definitely know if the cat is dead or alive - your nose will tell you. Especially in the warm weather we're having at the moment, your nose knows.

[@pietpaaltjes7419]

@@tarquinbiscuit-barrel5871 This IS an ex cat!

[@DataIsBeautifulOfficial]

Physics 101: Newton's apple in the fall, Schrodinger's cat in the spring. Repeat forever.

[@KenLieck]

In the universe where I live Newton was struck on the head by a banana and discovered the Law of the Jungle...

[@jayman912]

wait until you actually learn that Newton's apple did not fall but rather stayed still while the rest of the earth moved towards it! Looking at you@floatheadphysics

[@kronoscamron7412]

lol

[@magicmulder]

Darmok and Jalad on Tanagra.

[@simonc6328]

I have Schrodinger's memory. I can be told something that I've forgotten, but also remember it when it's become a problem.

[@MrGreasem]

Almost as good as knowing it's gonna be a problem but you can't remember what it was. LOL.

[@jamesbooth3360]

I can always remember that I forgot it!

[@krachr1]

@@simonc6328 my husband does the exact same thing. It’s like a reserve memory bank that can be utilized during a code red moment. The good thing is if it was in your memory to begin with hopefully you had time to consider a fix to implement when the code red emerges. This is worth study. The brain is so fricken cool!

[@TheEmpressPalpatine]

I heard about Schrodinger's voter. They are neither liberal or conservative until asked a specific question.

[@rupertchappelle5303]

Whenever I cannot remember something, I remember it later when it isn't important anymore. There is no cat.

[@Marvin-tpa]

I didn't realise my grandfather was so clever but he must have been because when he found a cat he told me that at the time it was half dead. I assume that the calculation also allows for the cat to be brought back to full life again and that's what my grandfather did.

[@AstroGremlinAmerican]

That cat was half alive. But I also am a so-called pessimist.

[@steffenbendel6031]

In the (simplified) mathematical model, you can resurrect the cat.

[@pomodorino1766]

Your granfather is the quantum vet.

[@KenLieck]

@@AstroGremlinAmerican Everything is relative. Give an optimist a bucket of shit to eat and he'll see it as half empty...

[@NostraDavid2]

*catculations

[@bushmasterflash]

Alice in Wonderland's Cheshire cat "What makes you think I am still in the box Mr Schrodinger?"

[@mikemondano3624]

Actually, I have asked that, too. You can't know if the cat is in the box for the same reasons.

[@kefhomepage]

If I know anything about cats …it’s probably just asleep 🤣

[@gad3]

😂

[@KenLieck]

You may be thinking of Schrodinger's parrot...

[@fractalmadness9253]

Which is just a cousin of death.

[@mynameis5427]

In a funny way, this is actually what is happening. The foundation of the Universe "sleeps" and "wakes up".

[@Alondro77]

If it was a parrot, it'd be pining for the fjords.

[@UCannotDefeatMyShmeat]

Shrodinger was known to mock some elements of the very thing people now think he took seriously

[@alfadog67]

Yes, I found myself in a similar situation last week. I realized that QM is a black box that provides probabilities based on hidden variable that we don't know how to observe. I could put a QM black box on the hood of my car to find the probability of it breaking down, or put one on my wrist to check for the odds of my having a stroke, or better yet, I could put one on a random timer (hidden variable) to put my cat to sleep. None of these processes describe fundamental nature.

[@bbgun061]

Yeah, I'm pretty sure he first proposed his cat experiment to show how ludicrous a quantum superposition is...

[@myfriendscat]

Humans sure complicate matters. You poor creatures, but we're here to help.

[@BigZebraCom]

This comment is hereby awarded two internets.

[@pantherman8719]

Lol your name and picture

[@KenLieck]

@@BigZebraCom Well, one must be the famed "dead internet" then...

[@JZsBFF]

That's the talk of every invader in history. Felix is no exception.

[@OzoneTheLynx]

I love how your user name is also a superposition of "my friends cat" and "my friend sca..." and I sure hope I live in the universe where it collapses to the former XD.

[@prettyfast-original]

3:31 The abstract says they observe an exponential increase in decoherence as the number of particles in a system increases, but then say that this suggests a solution to the many-worlds theory that does not rely on environmentally-induced decoherence. Are the "particles" not the "environment", or at least part of its makeup? It seems like the authors are saying decoherence results from time plus interactions; in which case, how is this new?

[@strangelaw6384]

maybe the novelty comes from the rigorous treatment?

[@aarionsievo]

If the result of simulated quantum interactions with these "many particles" (environment) is a collapse to classical (measurable) states, that would be at least new to me. That would enable to define a size boundary between classical and quantum systems but I think a non local collapse is believed to be impossible using the Schrödinger equation and I would be confused, if a local collaps can be described with Schrödinger but not a non-local collapse. Or is the relation to the wave-collapse I imply here incorrect?

[@strangelaw6384]

@@aarionsievo Huh? I didn't even know that Schrodinger equation supports a local wavefunction collapse

[@jeffryborror4883]

So they may have solved he dead+alive problem by omitting the the universe in which it can happen? My cats are not impressed. .

[@SabineHossenfelder]

Well, as I said, they chalked up the relevant assumption to a sentence about random matrices and the rest is a numerical calculation. So unfortunately, I don't know exactly what they did. It's just that I know that without making any special assumptions about either the environment or the system (what it means to be a detector) you can't solve the problem. Incidentally, Zurek (who come up with the idea of decoherence based environmental selection "einselection") knew this, which is why he tried to come up with system properties that would single out what a detector is. (Just that this didn't really work either.)

[@asandax6]

Are your cats alive or dead?

[@KenLieck]

@@SabineHossenfelder Maybe what we need is a lie detector...

[@jeffryborror4883]

@ Alive … for now.

[@MrGreasem]

Isn't it the case that parts of any given cat are alive, but other parts are dead, and being continually replaced by new cells? Baddaboom, baddabing, der ya go, solved it. Come to think of it, do we know something is not being replaced by the observation? Is the photon replacing something else? Is the particle "sticking" to the photon, or being knocked off it's wave?

[@HipolitoHernanz]

The vet came out of the examination room and said: "Mr. Schrödinger, about your cat, I have good news and bad news..."

[@LeksDee]

physics lately has just been "WE DISCOVERED SOMETHING HUGE AND SOLVED AN AGE OLD PROBLEM" and then you look at the paper and there's some assumption or detail missing that you'd need to check the results. Can we jsut go back to releasing complete research?

[@MyNameIsThe_Sun]

That seems to be the focus of this channel

[@stewiesaidthat]

​@MyNameIsThe_Sun nope. Sabine lacks the intelligence and critical thinking skills to do that. Suggest you watch her Special Relativity and the Twin Paradox video she put out. Here is what she left put. 1) synchronized clocks use the same amount of energy. How can you have real time-dilation when both clocks use the sane amount of energy. Instead of explaining, she tells you to shut up and calculate. Time-dilation has been decreed by Einstein. Do not question the word of your god Einstein. 2) the clock's cesium-133 atom is in a controlled environment. Being chilled to absolute zero and shielded from EM radiation. Is the observer also being shielded from UV rays? Placed in a freezer? You can't even compare the two frames. They are separate entities being accelerated at different rates. If have to ignore those two fundamental facts to get Einstein’s relativity nonsense to work. Sabine is either really stupid or great con-artist. Take your pick. Further proof? Gravity is not a fundamental force of nature. So why is it the focal point for all the models? Once again. Shut up and calculate. Don't question the word of your god Newton. F=ma. Force comes from Acceleration of the mass. Not the mass itself. F=G(m1m2)/R2. Force comes from mass? That contradicts the laws of motion. No matter what m2 is, F (motion) is always the same. Why is that Sir Issac Newton? The Laws of Motion, F=ma/a=a, requires an explanation for the source of all acceleration in the universe. Either acceleration comes from a creator god (let there be light) or Acceleration has always existed in an infinite/eternal universe. Newton couldn't very well say god created the universe and Giordano Bruno was burned at the stake for his infinite universe theory.

[@bluerendar2194]

Blame the media. Do you get that from the original paper title: "First Principles Numerical Demonstration of Emergent Decoherent Histories" In plainer english, using existing theories, we crunch some numbers on a simplified model and see something like decoherence happen! Or from wordings like: "This suggests a solution...." Plain english: Maybe this has wider implications, dunno? or on an assumption they made, "We deliberately point out that this attitude shall neither imply that the MWI is correct nor that the consistent histories interpretation of Griffiths is incorrect" Plain english: yeah, there's *some* (/s) disagreement about our assumptions and interpretations of these kinds of results. or, on the system they use "This is probably the simplest quantifier one can consider, but we believe its simplicity makes it appealing to get a first impression of what is going on." Plain english: this is of course an extremely simplified toy model, but the behaviour is still very interesting, and we should see if our first impressions are correct!

[@0nullBit]

age old?? this is not age old lol

[@GizzyDillespee]

Obvioysly not every paper is like that, and obviously not every video on this channel covers that topic. I think it's fair that, if you publish your research for peer review... if there's a challenge, often there's a back-and-forth in the journal. For a science educator who covers current topical issues, knowing that this is a popular aspect of quantum theory... it seems to be reasonable to push back on the article's claims, in this context. Plus... we watched it.

[@w0mblemania]

@2:09 Take a moment to think of the business plan behind creating stock footage of 3 middle-tier santas getting plastered at lunch time.

[@_leokratis_]

Could also be AI (have no idea if it is tho)

[@robertpenner8840]

without paying attention to the visual, I did a sort of auditory double-take when I heard this part. "wait a minute...did she just say...?" The most dead-pan delivery of dry humour....

[@hereticprimal5131]

I didn't even know that Schrödingers Cat was a Problem to be solved.

[@robfut9954]

Perhaps a superposition is just “shorthand” for a possible position that doesn’t matter in reality so it isn’t “drawn” into reality until/unless it acts upon something else in a meaningful way. Like how video games don’t draw scenes beyond the gamer’s view to save computer power.

[@skyhop]

A superposition is a discrete state not unlike normal states. What makes it different is that state is fragile to measurement, and will cause it to snap back into a classical state. It's not magic, nor is it peaking behind the veil. We just don't know how to measure it without influencing it. It's still entirely possible some method in the future may permit measurement without wave function collapse. Think of it more like angular rotation. Classical states would be at 90 degrees and 0 degrees, while a superposition may be at 45 degrees, or somewhere inbetween. Once again, it's a discrete state, and if we had the tools, potentially measurable.

[@airatshakirov]

No, It's more like all rendered objects beyond gamers' pov are become sum of all their models the moment the player turned his head away. So, instead un-rendered scene behind pov, in quantum mechanics scene behind player is full of mess and noize. If player is only one what interacted with objects by model-calling.

[@airatshakirov]

​​@@skyhopin superposition you will not see 45 degree result, you will see 90 and 0 at same time. Not any degree between. Quantum uncertainity and quantum superposition are different things. You can "measure" two "uncertain clouds" of one paricle in superposition state that can be in two places at one moment AND both of them will have uncertain position.

[@kronoscamron7412]

Yes , interaction collapses the wave function, that's basically it.

[@KRaimix]

Merry Christmas Sabine! ❤

[@mikemondano3624]

Good for you! Last Friday, I waited all day for a call wishing me a Happy Equinox. Not one call. We equinocturnals are people, too. If you prick us, do we not bleed?

[@KRaimix]

@ merry Christmas and happy new year friends with common interest ☺️

[@PointyTailofSatan]

I put a dead cat in the box. Now I have an undead vampire cat.

[@Thomas-gk42]

Maybe the universe splits every time a new cat video pops up on KZbin? Moment, I´ll work out the math for that THIS year.

[@AstroGremlinAmerican]

The Universe seem to split quite often. A trillionth of second? Time to read Kant on the infinitesimal?

[@Thomas-gk42]

@@AstroGremlinAmerican But not in this universe please😉

[@gregorygant4242]

" You spin me right round baby right round like a record baby right round round round !' Lol, lol !

[@bradleywilliambusch5198]

The cat is lithium based life in the dark.😂

[@bryancorrell3689]

I've always wondered why the cat isn't considered an observer.

[@fpsmeter]

Cat is an observer, but first and foremost, the particle detector which detects/does not detect radioactive decay is ALSO an observer (as it's a big macroscopic object). There's a lot of confusion about this experiment, simply because it does not need any cats. It only needs a detector to still be super weird. Cat's state is corelated with the detector's state anyway, so you can remove the cat out of the picture and STILL the problem remains. What's the problem then? Well it's simple. Mathematically, the expected result of the experiment that the detector should be in a state of superposition. So, at the end of the experiment we expect to see the radioactive particle DETECTOR in a state of "50% triggered, and 50% not triggered". Yet in the real world, the real detector either gets triggered or not. So what does that mean? Nobody knows.

[@fpsmeter]

One more thing, the root cause of the problem as I understand it is that the QM maths does not expect ANY "macroscopic observers" to actually exist. There is no notion of "wave function collapse" in the QM equations. All there is, is an evolution of wave functions in time, they can interfere, cancel each other out etc. but they never "collapse", i.e. a particle never really finds itself in any given point of space. The most profund thing is that this picture is NOT expected to change as the scale grows and as objects are getting bigger and bigger. There is no such size beyond which objects just stop having wave functions. They always have, no matter how big they are. Therefore, we should theoretically always be able to calculate wave function for macroscopic object, such as "detector" in the experiment we're talking about. When we do that, we get the following answer: "the detector is in state of superposition, it's 50% triggered, 50% not triggered". So, the mathematical expectation is that there should be no such thing as "single particle triggerring detector 50% of times", the expectation is that the whole detector enters the state of superposition. But in the real world, we see there is no such thing as detector stuck in superposition, it either gets triggered or not, with a chance of 50%.

[@gorkemvids4839]

observation is relative. even the scientists are in entangled superposition untill you read their papers.

[@otzmaanalytics4679]

@@fpsmeter I never understood why physicists consider this to be a problem, though. Just like the cat is correlated with the detector, we, who opened the box, are correlated with both of them. More precisely, the evolution of the system will diagonalise the states of the cat/detector and us. Getting to any other result requires a delicate balance of the relevant eigenvalues that cannot possibly happen in the real world. This is the description of the "Bare theory", which is fully compatible with QM, doesn't require multiple worlds, and has no notion of an observer or a collapse of wave functions.

[@pierfrancescopeperoni]

In the relational interpretation everything is an observer, and superposition is relative.

[@jensphiliphohmann1876]

Schrödinger's cat: Both alive and dead Normal cat: Either alive or dead Sauron's wraith cat: Neither alive nor dead

[@GeoffV-k1h]

Matrix: There is no cat.

[@LeopoldoGhielmetti]

Portal: The cat is a lie

[@syntaxusdogmata3333]

Hamlet: To cat or not to cat.

[@FLPhotoCatcher]

Dante's meme cat: Has Cheezburger, but can never eat it.

[@antjoj5996]

Reservoir dogs: that's the smallest cat and it's meowing just for you

[@luminiferous1960]

The wavefunctions in quantum mechanics are probability amplitude functions, the magnitude squared of which gives the probabilities of the outcome of a measurement over all possible outcomes of the measurement, and the possible outcomes of the measurement are the eigenvectors of the observable operator which characterizes the measurement setup. While the state vector representing the wavefunction can be written as a linear superposition of the observable operator eigenvectors, that superposition state vector is not itself one of the observable operator eigenvectors and therefore, is not a possible measurement outcome, unless that state vector happens to consist of only one observable operator eigenvector, but in that case the state vector is not in a superposition state but in a pure state instead. In the Schrodinger's cat thought experiment's measurement setup there are two eigenvectors of the observable operator with one eigenvector representing the dead cat and the other representing the alive cat. While a linear combination of a dead cat and an alive cat is an allowed superposition state of the cat's probability amplitude wavefunction represented as a state vector, it is not an eigenvector of the observable operator and therefore, not a possible result of the measurement. Since it is built into the mathematics of quantum mechanics that the superposition state is not a possible observable state, the real issue with the Schrodinger's cat thought experiment is that the mathematics of quantum theory does not specify how the collapse of the wavefunction to the specific measured value (or equivalently, how the superposition state vector projects to only one of the observable operator eigenvectors) occurs, i.e., the measurement problem. In my view, the measurement problem is not a problem. The quantum wavefunction represents the complete probabilistic knowledge we have about possible states of a system at a given time. When we perform a measurement, we merely obtain new data about the system. In this view, since the wavefunction itself is not a physical phenomenon, but instead an accounting of the probabilities of possible outcomes, the wavefunction doesn't physically collapse into the measured state during a measurement, but rather the data we have about the system is updated based on the measurement outcome.

[@D1N02]

The cat is part of the universe and will 'know' wether it is alive or dead. No human measurement is needed because the universe is a self measuring system. Measurement always takes place at the lowest possible level first. Ergo amplification of quantum uncertainty is not possible if there is a measurement happening. Measurements almost always happen. Measurement is just the same thing as interaction.

[@nick_john]

…so the song “Yer Blues” was sung from the cat’s perspective? I never knew that.

[@jdlech]

If the universe is a self measuring system, then why are there waves at all? It seems to me that a self measuring system would have completely measured itself in the past 14 billion years (or so) This strongly suggests that the universe is at least only partly self measuring. If so, then we have to find out the limits of this self measurement, and why there are limits in the first place.

[@D1N02]

@@jdlech waves are the very essence of our dimension, which is emergent. Waves is how everything emerges and creates spacetime. Time is not a property of the underlying universe, where we emerge from, but emergent itself. The source is timeless and thereby eternal.

[@erinm9445]

It's worse than that. What is a gieger counter if not a measuring device? You can't get to the point where poison is administered to any cats without triggering collapse.

[@amihartz]

The most consistent interpretation is relational quantum mechanics. RQM views the "observer" as any possible reference frame defined by an object that is used as the zero-point (the "origin") of your coordinate system to describe everything else. This "observer" can be a human, a cat, a rock, or even a single particle. Descriptions of a system will be different from different frames of reference (that's why it's "relational"), for example, from the cat's frame of reference there is a definite outcome prior to opening the box, but from the human's frame of reference there is not. In RQM this phenomenon is known as the relativity of facts. *_Every object can be considered an "observer" and any interaction at all can be considered a "measurement" depending upon the chosen reference frame._*

[@traviscecil3903]

Looks at box and says... "Dead or alive, you're coming with me."

[@BerndSchnabl]

This was solved a long time ago. It died! No cat could survive 100 years in a box.

[@dw620]

It's a lot quicker if the "environment" in question is interstellar space.

[@tvviewer4500]

In a quantum box the cat could live always

[@Coolcmsc]

😂

[@kronoscamron7412]

CAT : tell Schrödinger I survived and I will find him.

[@OhNoNotAgain42]

Little known story about Schrödinger: He was given a gift of a pet opossum by his brother when he turned 21. He took the opossum everywhere in his early days at university and during his research years. He was constantly seen in his laboratory with the opossum right as his side. His friends used to joke that it was his research assistant” as it was always on the table when he did his experiments. During this time, he was really struggling to make a name for himself and none of his work was yielding any meaningful results. One day, the opossum died and Schrödinger was devastated, it had been his companion for so long. A bunch of his friends bought him a kitten to keep him company. Schrödinger tried to treat the kitten the same, bringing it with him while he did his work. He never really bonded with the kitten, but, all of a sudden, his work came together and he made his greatest contribution to science. He realized what the problem had been all those years… the opossum was always playing dead.

[@glennchugg6015]

To Answer the question you need to give it an observable time period, once you add time length it will only be in one state at that time, for the super position to be an actual usable tool you can think of it more like mixing colours, it's only the observations that change, the original colours are still the same, but as you can't un-mix them, the observed state is often the new colour, the thing that makes it a usable thing is you can then use more time to mix in another colour and get the combined results. It's an analog system, not digital - which is how the super position is even a thing.

[@msromike123]

MWI just seems like a stopgap until we have better tools for measurement, and better math to make sense of quantum theory. In my mind, MWI is akin to Ptolemy's geocentric model of the solar system. The Ptolemaic model was useful at the time and accurate enough to make usable calendars and whatnot. But it was a flawed model that did not line up with reality. Development of the correct model did not diminish his achievements.

[@Verlamian]

You'll be pleased to learn that no better tools for measurement are needed and that we've had that better math - or rather a better understanding of the math of QM - since before Hugh Everett published his MWI paper. Furthermore, Schrodinger, in his famous "cat paper", was highlighting a problem not with QM itself but with a naive "semi-classical" interpretation of the quantum state ("wavefunction") that was still considered tenable by some at the time. Ironically, the MWI is similarly plagued by such profound conceptual and mathematical problems that it's hard to understand why *anyone* does still take it seriously (relatively few "quantum foundations"-literate people do).

[@innocentsmith6091]

Except you don't need MWI to do anything.

[@msromike123]

@@Verlamian Ok, I am obviously a lay person, but I thought the reason for MWI is it is a way to bring immeasurable phenomena (that may not actually exist) into a model that allows for actual applications of the model to produce something useful (quantum computers for instance, though that is debatable in terms of their usefulness.) Thus, my analogy of creating accurate calendars from a model that had no basis in reality. I am just trying to put this all into a context that I can understand.

[@Verlamian]

@@msromike123 Thanks to the "Born rule"* one doesn't actually need anything more from the theory for useful applications than what's already there. You may have heard the expression, "shut up and calculate" which refers to an attitude adopted by the majority of physicists for a long period after the theory's birth. What the MWI does - attempts - is to go further and provide us with a full "Interpretation": a detailed account of the meaning of the mathematics in conceptual, physical terms. * The MWI actually drops that crucial "Born rule" from the theory, temporarily at least, and attempts to (re-)derive it.

[@msromike123]

@@Verlamian Perfect! After reading about the Born rule just now, that puts it into persepctive.

[@electrifiedspam]

The real problem is that physicists assume the cat is in a vacuum with no friction. That's why it always ends up dead...

[@DanielFoland]

0:34 all I know is that now I am in a super-position to make some lame puns, puns so bad it'll make ya psi...

[@LyonWalker-bu4ph]

I didn’t realize it was a problem to be solved. I thought it was a metaphor meaning you don’t know until you know.

[@CommackMark]

I always thought the thought experiment was to point out that when scaled up to everyday physics the quatum physics became absurd. It wasn't to suggest the cat was really alive and dead at the same time.... so what's to solve?

[@dgjanes917]

That's exactly what I thought.... The cat is a metaphor for a particle in superposition, and the poison is part of the method by which we observe the state of the "cat"

[@jamescomstock7299]

The reason this is still being discussed is even though the thought experiment was proposed as an obsurdity, we have yet to prove it actually is with our best models of the universe. Meaning, obsurd sounding or not, it still might actually be true.

[@mikemondano3624]

Not at all. "Superposition" is a statement of our ignorance of what is happening. It's a made-up state that means nothing other than "We don't know so we'll name it so people won't find out." You don't really know if the bread is in the breadbox until you look, either.

[@scottbradley3372]

I agree, the cat is never in super position, observed or not.

[@amihartz]

Yes, Schrodinger opposed the idea that particles literally are "smeared out" in multiple states at once. Schrodinger argued that this belief arose from people trying to fill in the "gaps" between interactions. If you measure a particle _here_ and later measure it _there,_ Newtonian mechanics tells us that it must have continuously traveled from _here_ to _there_ in between those interactions, when nothing was interacting with it at all. However, in quantum mechanics, you cannot always fill in the "gaps" between interactions in this way without running into contradictions (like the measurement problem). Schrodinger argued that we should just abandon trying to fill in the gaps, that maybe, at a fundamental level, particles just "hop like fleas" from interaction to interaction (a phrase he initially used to disparage matrix mechanics, before later changing his mind to agree with it).

[@zxuiji]

4:14 It was roughly when this slide or whatever you call it popped up that I started to think quantum state is similar to semaphores (a programming tool for thread synchronisation). Until you lock the semaphore you never really know what state the semaphore is in accept the brief moment that you looked at it while trying to lock it or release it.

[@My-Pal-Hal]

I Solved That DECADES AGO. Just ask the Dog, if the cat is okay 😂 ... try to keep up people

[@dalehill6127]

It's nice that the video came with a quiz but I was half hoping it might come with a cat that I could determine was alive. Thanks for your many fine videos Dr Hossenfelder, merry Christmas and a happy New Year to you and Albert. 👍🏻🤔👎🏻🐱😀

[@calebgriffiths9062]

Schroedinger was probably thinking that the mathematicians needed to improve their maths. Maths souuld be the servant, not the master.

[@-danR]

Schrödinger wasn't presenting a 'problem' to be 'solved'. There was nothing that needed improvement. He was presenting a parody, and asking physicists, "Do you know what you are entailing? Have you really thought this through?"

[@Hylianmonkeys]

Math is all our master.

[@timothyvanderschultzen9640]

Math is a tool.

[@zappulla4092]

@@timothyvanderschultzen9640spoken by someone who doesn’t understand math. It’s an abstract system that allows logic and reasoning. A foundational framework to better understand patterns, relationships, and structures in the universe. A ruler is a tool. Without math it would have no value.

[@johnwollenbecker1500]

I never knew where to plug in the remaining life count.

[@franciscoatwi5280]

Thanks Sabine, this video was very informative and I’m trying my best to understand the system and the environment as a scientist.

[@michaelripley4528]

The pet cemetary solved it decades ago! Cat was a Living dead! And a dead Living cat🤣

[@EonityLuna]

“The Schrödinger's cat paradox outlines a situation in which a cat in a box must be considered, for all intents and purposes, simultaneously alive and dead. Schrödinger created this paradox as a justification for killing cats.” - Fact Sphere, Portal 2

[@VariantAEC]

He could have used bananas... but he chose cats.

[@Alondro77]

The core problem with the many worlds hypothesis is obvious: every single quantum interaction results in the formation of entirely new universes... meaning each wavefunction has the potential to generate an entire universe's worth of energy from absolutely nothing. And that this is happening an uncountable number of times every nanosecond. And if the excuse is that all these universes always existed, then the direct implication must be that they are all intrinsically entangled such that 'outcomes' of all these possible quantum paths exist, which could not be the case if they were truly independent. Either way, it creates a very big mess of un-testable gobbltygook. I think it all just means that we don't fully understand quantum mechanics yet. Usually when we get crazy predictions for something, it ends up meaning we're missing some crucial information.

[@leviosaaa9005]

First law of energy u can’t create something out of nothing, so learn more

[@recurrencetheorem4264]

No that is not what MW claims. Sabine is incorrect in the language she uses here. There is only one universal wave function in MW that is partitioned, there is no "creation" of new universes as the total energy is redistributed. The universal wave function will encompass all the possible trajectories and therefore represents a derterministic hypothesis. Nothing "new" its already there ... just lays out all outcomes. Obviously I am no position to say this is correct but it is often misrepresented or confused with multiverse hypotheses.

[@Alondro77]

@@leviosaaa9005 Uhm, if you actually read my post, that was the point. The universe would have violate that first law CEASELESSLY be generating infinite minutely different versions of itself. You might as well believe in every single god in every single religion in that case, because there'd probably be a bunch of universes where they existed! Also Thanos, Akira, and Lord Freeza. lol

[@gary.h.turner]

Isn't the Many Worlds hypothesis about the many POSSIBLE worlds that COULD exist? None of these future worlds have ANY actual energy until one of them is chosen, then the chosen world has ALL of the energy of the previously determined world.

[@recurrencetheorem4264]

@@gary.h.turner The MW hypothesis is to obey the Shrodinger equation at face value. There are no chosen worlds as the Schrodinger solutions allows all superimposed states to evolve independently since they are orthogonal to each other. There is no need for the magic of "collapse". There is no violation of energy conservation as there is only one universal wave function with a constant amount of energy. The sum of all superimposed states is equal to the state of the universla wave function. There actual are no "new" universes created.as new worlds extract from the system energy and therfore each branch "thins" out. MW is deterministic where you can think of the universal wavefunction containing all possible trajectories... all the futures are already written. Those that are posting that MW violates energy conservation are ignorant to the details of MW.

[@amihartz]

1:30 this wave function is technically wrong, as the wave function would be an entangled system involving the entire contents of the box and not merely the cat. The cat on its own, you could only find its state by doing a partial trace to get its reduced density matrix, which in that case you would find that the cat's state on its own would not exhibit interference effects.

[@Jeffron71]

What I've never understood about this is that surely the cat itself is an observer. It would experience whether it's getting poisoned or not.

[@ozymandias4385]

quantum state do not care about "observer", decoherence applies when an interaction stronger than plank constant happens. but when you observe smtg, it means that light reverb on it (or that you throw electrons/particles in the direction of what you want to know the position of), so you break quantum state (unless in very low temperatures and knowing what you are doing). by saying quantum state depends on the observer, what we realy say is that it depends on the measure, or more precisely on the interraction. (it has nothing to do with concioussness) (sorry for my english, i'm french so it might not be very clear)

[@iamnietta1940]

So basically these guys are trying to achieve or solve quantum zombies. Good. I get it now.

[@vivica8207]

Im still lost.

[@amihartz]

The most consistent interpretation is relational quantum mechanics. RQM views the "observer" as any possible reference frame defined by an object that is used as the zero-point (the "origin") of your coordinate system to describe everything else. This "observer" can be a human, a cat, a rock, or even a single particle. Descriptions of a system will be different from different frames of reference (that's why it's "relational"), for example, from the cat's frame of reference there is a definite outcome prior to opening the box, but from the human's frame of reference there is not. In RQM this phenomenon is known as the _relativity of facts._

[@rhonda-my_honda_cb500x3]

@@amihartz "In RQM this phenomenon is known as 'the relativity of facts'". Same thing happens in Politics too🤣

[@SOMNIOHM]

_The cat is indeed both dead, and alive!_

[@DrEhrfurchtgebietend]

Schrodinger did not propose that this was true. He he used it to illustrate how dumb the copenhagen interpretation was

[@bobaldo2339]

And still is.

[@ampman5863]

Already said in both the video and its description below it.

[@ricomajestic]

Which Copenhagen interpretation? There are like 4 different versions of it!

[@patrickgravel9261]

Absolutely, sensationalism and attention grabbing is the new norm.

[@innocentsmith6091]

Less dumb than the MWI

[@radastir]

Chuck Norris rescued the cat and locked Schrödinger in the box. Now it is alive - end of discussion.

[@disgruntledwookie369]

Yes, I agree with some slight variation of many worlds. But I think the answer to why we never see a superposition is because it is logically impossible to perceive something indefinite. What would you perceive? Superpositions are indefinite states, they are partly this, partly that, somehow not entirely anything. How could you ever experience something which is somehow a combination of mutually contradictory states? If I tell you the coin is a superposition of heads and tails, then you look at the coin, what do you see? It has to be something, if you perceive the coin it must be either heads or tails.

[@nolanr1400]

Exactly. It's all about perception or I would rather say consciousness. Our consciousness can only perceive one of the infinite number of states that exist and keep existing simultaneously that we are not conscious of anymore and forever

[@disgruntledwookie369]

@nolanr1400 you have to be careful using the word consciousness among physicists, it makes them uncomfortable 😜

[@jamescomstock7299]

You neglected the rare edge state for the coin. It's quite likely the truth of Schrodinger's cat is just like that... Another real-life option not discussed as an option in the thought experiment.

[@winstongludovatz111]

Superpositions are not partly this and partly that. They are something new that can create interference effects, such that e.g. there is nothing where naively we would expect to be something.

[@disgruntledwookie369]

@@winstongludovatz111 The key part of my sentence was "not entirely anything". A superposition is mathematically a linear combination of states. Interpretation is another thing, pick your poison. The Copenhagen interpretation would say that the superposition has the *potential* to be either this or that. When I say "partly this" I don't mean a mixture, it's not a recipe for a cake. I don't know how to explain without appealing to the math... A general quantum state can be decomposed into an eigenbasis, with a coefficient in front of each basis vector which represents the projection or degree of overlap from the general state to the eigenstate. Would you not say that a general 2D vector points partly in the x direction and partly in the y direction? It is the same thing. A superposition is an indefinite state, it is not 100% anything. Superposition can lead to interference, yes, but that's just focusing on the double slit experiment. One man's superposition is another man's pure state, it depends what you're measuring. If you have a spin-up electron and you measure the up/down spin you will get spin-up 100% of the time. But if you took the same electron and measured its left/right spin you would get left 50% and right 50% of the time. Superposition is a much deeper idea that just interfering waves.

[@DoctorOnkelap]

observing decoherence in a pub indeed

[@KenLieck]

Or incoherence at de pub...

[@DoctorOnkelap]

@KenLieck and if you see double it solves the problem as there are two cats then

[@onetwo1817]

@@KenLieck Brilliant!😂

[@silvio5266]

Sabine have you heard about the study on plasmoids? There is a 109 page study published in the journal of modern physics (I know it's not peer reviewed, but it's worth looking at). It would be really interesting to have an informed opinion from you

[@patrickgravel9261]

As soon as you mention many worlds or multiverse, I think of dragons and wizards. Plausible but highly improbable.

[@amihartz]

Both hidden variables and multiverses are driven by the same thing. Many physicists are just distraught by the fact that quantum mechanics is nondeterministic. They strongly believe in determinism and it bothers them to no end that quantum theory is random. Hidden variables are difficult to make viable because they violate special relativity, so many worlds is an attempt to restore determinism without having hidden variables, just by claiming that every possible outcome really does happen in a grand multiverse in those exact proportions, so the wave function is not merely a list of probability amplitudes but describes the physical distribution of branches of the multiverse. It's deterministic, but also entirely disconnected from anything we can ever observe.

[@DrStevenDPM]

Wonderful timing! Fits well into my current manuscript on relationalism, where time in our reality begins (t=0) at a collapse into a single state, meaning quantum superposition state exists in non-time, collapse into single state creates t = 0 (unchanging) in our real-world system (relational timeline), and with motion/change (where time cannot equal zero) we preceive this reality and relational timeline.

[@rindernetz1061]

So the cat is just undead? I knew it!

[@SNixD]

That explains the multiple lives thing they seem to have going

[@edwardpotereiko]

A superposition between being dead and alive still sums to a state we classify as alive to some degree. This says something about classifications being classical yet still not trivializing the role of the observer.

[@tian5797]

Why scientists just don´t wait for cat to meow to find out? Are they stupid?

[@Thomas-gk42]

Schrödinger, standing beside the box, to the audience: "The cat in there is in a superposition, we can´t know if it´s dead or alive" Cat: "Meow" Schrödinger: "Shut up!"

[@JZsBFF]

One can blame theoretical scientists for being a lot of things but stupid? Nope. It's cats which pose as smart but in fact they're pretty dumb.

[@howtoappearincompletely9739]

2:00 That visualisation for decoherence is breathtaking! A beautiful choice, Dr Hossenfelder.

[@Liberum69]

The superposition went away when the detector detected it to release the poison, or didn't. The cat is also an observer. Why is this hypothetical still being used?

[@janzibansi9218]

because it sounds cool

[@tomasblack6157]

Its a very abstract hypothetical. You have to treat the cat as an unobservant quantum system

[@BackTiVi]

It has always bothered me as well. If the poison is released only if the atom has decayed, then just that verification should collapse the wave function and end the debate before the cat even had the time to die. Now maybe I haven't really grasped all the premises of this problem.

[@AM-bw3ze]

What makes the difference between an unobservant and an observant quantum system? The interactions with the environment?

[@felixhex]

yep no mystery to begin with paper makes thusly no sense

[@diegofloor]

The thing about superposition that is really strange is, why is this not just a probabilistic thing? you can create a superposition in classical systems too, by flipping a coin and hiding it from sight for a while. I know it's not the same thing, but that part of the reasoning is rarely explained, and a lot of people are left wondering what's so mysterious about superposition in the first place. And yeah, I know covering Bell's theorem usually falls outside the scope of these expositions.

[@Verlamian]

In fact it is just a probabilistic thing. Mathematically, QT is an algebraic generalization of (Kolmogorovian) probability and classical mechanics can be and has been written in the exact same formalism ("Koopman-von Neumann CM") - superpositions included. There are important conceptual and mathematical differences of course but you won't hear about this stuff from the scandalously prevalent - and prominent - "quantum foundations"-illiterates who make numerous serious mistakes and can't even be relied on to correctly relay the content and context of Schrodinger's famous "cat paper". Excuse the bitterness. 😫

[@mattlewis5095]

sounds like another incomplete paper

[@etc4xg]

Papers are like measurement: true, false, or unresolved.

[@jonjohns8145]

Seeing Gus Sorola from Rooster Teeth in a Sabine video about Quantum states is NOT what I expected to happen today.

[@arctic_haze]

The moment I heard "many words interpretation", I became disappointed. I do not like multiplying universes any time a particle decides it is measured (whatever measurement actually means)

[@andreasvox8068]

That's not what happens. You are in different universes all the time. When you measure, you just find out in which one you are. No branching required.

[@1112viggo]

lol i realize its just a typo but "many words interpretation" has really good joke potential for some of these theories.

[@mensaswede4028]

Well, everyone said the same thing about the earth revolving around the sun hundreds of years ago.

[@brothermine2292]

There's no need to multiply universes. In the simplest -- therefore Occam-favored -- version of Many Worlds, there have always been an infinite (or finite but vast) number of universes, and there isn't any "branching" that increases the number of universes when a "measurement" is made. Instead, the measurement informs the experimenter which subset of the multiverse her own universe is in. For example, she learns she's in a universe that's in the subset in which the cat has been dead for awhile (it died before the observation is made) or she learns she's in a universe that's in the subset in which the cat didn't die. (There are also other universes in which the cat wasn't placed in the danger box, but the experimenter already knew from her memories of preparing the box & placing the cat in it that her universe isn't one of them.)

[@1112viggo]

@@andreasvox8068 But if you jump between different universes all the time, how does that avoid branching?

[@spiritualityandscience]

Sabine, is your name "Sabine" ? Sabine: I'm very sceptical about it.

[@ScottJPowers]

when you add positive and negative numbers of equal amounts, they just cancel out. So perhaps you could say that about the math that is being interpreted as saying the cat is both dead and alive. But, as I see it, these quantum wave functions only describe a range of possibilities given a lack of information, but all these possibilities are not going to be simultaneously true.

[@knutholt3486]

You said what I too planned to say.

[@amihartz]

The issue is that if the system has a definite state and the probabilistic description is merely due to a lack of knowledge, then in objective reality the state of the system would be 0% or 100%. Neither of these numbers have negative signs like quantum probability amplitudes do, and so they could never cancel out with other probabilities, i.e. they would never exhibit quantum interference. It makes no sense to say that objective reality cannot exhibit interference effects but only our subjective knowledge does, when we do actually observe interference effects in objective reality. You have to treat it as if it is genuinely random and not deterministic, meaning there is no definite state of the system prior to you observing it. Well, this isn't an "issue" per se, there is no mathematical contradictions here, it just does not jive well with most contemporary philosophy.

[@oldbrokenhands]

Physicist have slapped me around so much with this, I can't tell if I'm alive, dead, or both.

[@michaelb7498]

SHRODRINGER DID NOT BELIEVE IN THE CAT IN THE BOX THEORY. HE MADE FUN OF THE ABSURDITY OF THE IDEA. LOOK IT UP

[@trdi]

Starts at 3:30 Ends at: 5:25 I miss the old format with fewer longer videos, where they went through multiple stories, with ratio between content and fluff being better than 30%. It's pretty much why I don't click on many of the videos any longer.

[@carlbrenninkmeijer8925]

A Nobel Prize for Cats?

[@Barryhatchet]

Robocop cat. Dead or alive, you’re coming with me.

[@blinkingmanchannel]

We really need some way to get more data about electrons so we can stop chasing our tails on this entanglement idea. (I think…) I’m prolly not really getting it, but it looks to me very similar to the situation in which you can have two roots in quadratic equations. 2*2=4, but so does -2*-2… We don’t worry what it means in reality that there can be two answers to this math question. Why are these wave functions any different, except that we’ve gotten used to using the math to predict physics results. Because we’re having a hard time measuring anything at that 4nm scale, let alone anything smaller.

[@munbruk]

The cat is alive as long as we believe he is alive lol

[@djayjp]

Harvard's Dr Jacob Barandes has a local realist interpretation of QM that doesn't feature superposition and yet yields the same predictions as QM.

[@Dr.Gunsmith]

I’m telling you now in my universe my cat it’s surely alive…its making a right mess 😂

[@56nickrich]

A cat is not a quantum particle and doesn't have the same reactions to theories as easily as sub atomic stuff does. The cat is either alive or dead or non existent.

Thank you Dr. Hossenfelder. Greetings from a bioeng grad student, in Popayan, Colombia.

[@albawehunt]

[@albawehunt]

I raised 175k and Maria Luisa Clare is to be thanked. I got my self my dream car 🚗 just last weekend, My journey with her started after my best friend came back from New York and saw me suffering in dept then told me about her and how to change my life through her. Maria L. Clare is the kind of person one needs in his or her life! I got a home, a good wife, and a beautiful daughter. Note!:: this is not a promotion but me trying to make a point that no matter what happens, always have faith and keep living!!

[@Michael1_v]

+1🇺🇲

[@Michael1_v]

533

[@Michael1_v]

0701🇺🇲

[@Michael1_v]

communication with her incredibly efficient and highly reliable with whats~App's💞

[@david_porthouse]

Alexandre Chorin has shown us how to do a computer simulation of the Von Kármán vortex street in two dimensions using clouds of point vortices in Brownian motion. Arguably this begins life as a Monte Carlo method, and both Chorin and myself have used the method to reconstruct the Blasius profile for a simple laminar boundary layer. The question in quantum mechanics is whether or not there is a way to introduce randomness which is fundamental and not merely a Monte Carlo method. The random breaking of a vortex street from above or below may resemble what happens to Schrödinger's cat. The catch is that in quantum mechanics we cannot add the randomness in a way that changes the Schrödinger or Euler equation into another equation like the Navier-Stokes equation, because we would be predicting things that are simply not observed. I have proposed adding what I call tachyonic Brownian motion, but let’s hear other ideas. Another catch is that while Chorin's simulation runs in polynomial time, a similar quantum mechanical simulation may require exponential time. This isn't an easy subject! What I should do at some point is to produce the vortex street and Blasius profile simulations in Excel VBA so as many people as possible can download and run them at home. I could also offer an option where vorticity is quantised just so that the quantisation parameter and the Brownian motion parameter are set equal. This will be plan B while I am thinking how to tackle exponential time issues. I have so far produced a simulation of an electron in a dipole magnetic field (i.e. the Van Allen belt) called *stormer.xlsm* which can be tracked down on ResearchGate and downloaded without a password. Dr Hossenfelder doesn't think much of ResearchGate, but has not indicated any better platform. If nothing else, *stormer.xlsm* shows how to do three-dimensional programming using vectors in Excel VBA, where two modules are required. Highlight the name of the program, right-click and left-click to track it down. It is fairly likely to be the first item in the search.

[@LairdPrydae]

I tried explaining this exact issue to my accountant. Foolishly, he tried to affirm that my account was indeed empty. I spent the better part of an afternoon failing to convince him that, mathematically, that was impossible. He simply didn't know where to look.

[@RandallHelzerman]

Its nice to have a presenter who can actually pronounce "Schroedinger".

[@johngough2958]

Is the actual paper you're talking about by Strasberg and Schindler? The link is to something else by Hall which seems to be a critique!

[@SailingGoonies]

The reason why a photon doesn't show its resulting path until viewed is because it makes both potential paths possible at the same time, 1 time line result for one and another time line result for the other. Once observed the timeline is set.

[@MrRolnicek]

I would REALLY love to see Sabine talk with Sean Caroll about the many worlds interpretation and it's problems.

[@recurrencetheorem4264]

Sabine misrepresents MW in her videos and Sean already knows the challenges with the hypothesis.

[@MrRolnicek]

@@recurrencetheorem4264 Misrepresents is a strong word, I don't think that's quite true but yes I'd mostly like to hear what she has to say against the extremely convincing things that Sean has to say about it.

[@recurrencetheorem4264]

@@MrRolnicek Yes it is a true misrepresentation to say that many universes are created relative to the hypothesis stated in both Everett's work (1957) and Sean Carroll's work (current). Sean defines ONE universal wave function that obeys the Schrodinger equation. The superimposed states are "components" of the universal wave function, not magically generated new universes. No one is in a position to say MW is correct, but it is true that the MW hypothesis is misrepresented by saying new universes are created which leads many to belive there is a conservation of energy issue. It is unfortunate that out of convienience even the "professionals" are not precise with their language.

[@ShimrraShai]

I think I _may_ see what they're trying to get at in this paper, and it sure is interesting. While I have not parsed through anywhere close to the math, the gist I am getting is that they seem to have supported something that can be understood in the context of the following intuitive argument. Note that one of the assumptions seems to be that the system in question has a finite-dimensional Hilbert space, viz. that there is only a limited amount of _configuration_ -space "room" available. A finite grid of points, to be precise (think a qubit - its configuration space is the discrete set { 0, 1 }, and for 2 qubits, it is { 00, 01, 10, 11 }, etc.) For decoherence to occur, there must be separation of branches - "humps" of the wave function as viewed as a "surface" plotted a top the (multidimensional) configuration space at "likely" configurations. Because the configuration space is limited and bounded, however, Schrodinger evolution at arbitrarily long time will cause "recoherence" or recollapse of decohered branches back into a superposition due to "running out of room" for them to branch into, which one might be tempted to call a "quantum apocalypse". Note that the number of branches grows exponentially, so we can expect it to eventually "hit the ceiling" in not too long, even with a large configuration space. One can think of this kind of like the Poincare recurrence theorem (it may even be the same thing). What it seems their result is, at least intuitively, is that the boundedness of this space not only eventually forces the branches to all recohere to some end point, but in fact its effect is "more severe" in that the constraint it imposes prevents all of them from even decohering in the first place. Instead, a more limited number of decoherent branches comes off, together with remaining-coherent "lumps". And the decoherent branches just happen to be ones that have approximately (presumably exact in some infinite limit) Born rule characteristics. It would also mean that in that restrained configuration space universe, it would be impossible for the embedded observer to experience certain histories at all. Now that could be all wrong, but that's how it feels to me. Put more simply, it would mean the "extra assumption" to derive the Born rule from the Schrodinger equation is simply "the Universe has a finite number of configuration states", like a qubit does, even if very large. It has a finite total information capacity and is a closed system. Conversely, one might want to argue that our observance of the Born rule is evidence (not proof) for these assumptions, and likewise if we found an "unusual" effect, it would show that one or both were broken (think hypothetically, e.g. if someone proved scientifically a real ghost: such a thing would break the closed-system rule for the Universe, and thus would permit the needed Born-rule violation to make it happen). But more interestingly, it hints that even if it is not absolute, the Schrodinger equation "likes" the Born rule and so while some extra assumption would still be needed to derive it in unlimited/infinite cases, that assumption potentially may be made very mild.

[@elbenny68]

Maybe the Cat is just sleeping...

[@tsbrownie]

Plot twist: The cat was never in the box.

[@rokasb9441]

So in short, the cat is "wanted dead or alive"

[@jamesbooth3360]

So if I deliver the box with proof that the cat is inside, can I collect two bounties?

[@david_porthouse]

One computer simulation which I would like to see is a wave packet passing over a potential well. We would do comparative simulations of the Dirac equation and the Schrödinger equation with the rest mass term retained. These are both very stiff equations, but we can use a three stage prepredictor-predictor-corrector method with the prepredictor doing an initial analytical integration of the rest mass term only. The electromagnetic field would be modelled by a semiclassical method, and is there simply as a way to dump excess energy (I am not trying to model correlations between photons). The potential well is a dimple in an object heavier than the Planck mass, so I will wave my hands and give it a bit of classical Brownian motion on the scale of quantum mechanics. This complies with the requirement imposed by me to make use of a random number generator. The RNG would be the Mersenne twister to begin with, but it would be reseeded every time we press a button by reference to the time of pressing. Buttons can be provided to do a time reversal or a replay of the cinematic loop output system. The curiosity of the user would in effect drive a genuine RNG. I want to try this simply for the sake of curiosity. No claims are being made. This will be our first view of the interaction between the wave function, the electromagnetic field and a bit of randomness. Once the simulations are up and running in Excel VBA, I will aim to put them on every computer on the planet with the source code being accessible. Maybe then someone a lot cleverer than me will work out something better. My expertise is with the Navier-Stokes equation, not quantum field theory, Hilbert spaces or Clifford algebras. However experts on the latter subjects could be dunces at computer simulation, so perhaps there is something to teach them. I am also lightweight in my knowledge of Maxwell's equations, especially on the difference between the Lorenz and Coulomb gauges. I will try writing a few simulations to improve matters. Devising suitable boundary conditions for the various equations is still an outstanding problem. Cyclic and reflective conditions are easy enough, but we need a transmissive condition at least for Maxwell's equation, or maybe we just fill the whole simulation with "fog" to get rid of unwanted electromagnetic energy. With a transmissive condition for the Dirac equation, we may encounter the fermion doubling issue reported by other workers. This is why comparative studies of the Dirac and Schrödinger equations will be pursued.

[@BillyMcBride]

Thanks, Sabine! So, superposition is just a version of uncertainty?

[@cougar9902]

Sabrine, I notice you publish new video every day? How's that even possible?

[@michaeltoney2277]

Was I right? Was he eating treats in the kitchen the whole time we’ve been thinking about that box?

[@bsl2501]

Awesome shoutout to the team! Well done, well done.

[@edwinscheibner7941]

Thank you, Sabine.

[@woowooNeedsFaith]

Isin't the original problem itself flawed already? Detector at 1:20 has to make an observation of the decay before it can trigger the poison, right? I of course don't understand how detection of superpositions or propagation of superposition states is suppose to work, but that detector should make a decisive choice before it can act on macroscopic poison source, right or wrong?

[@Allyfyn]

I was thinking so as well

[@Slash27015]

So is that what they refered to in Futurama when that guy says he has a cat in his box that's in a superposition of both alive and dead

[@vslabs-za]

Dead? Alive? There is no spoon.... er, I mean cat.

[@rudolfquetting2070]

I think, Schrödinger did publish his thought experiment, not as a physical fact, but as an parable. Mathematically, a superposition is obtained by a certain operation (usually addition) in a vector space. But the states „dead“ and „alive“ are no vectors at all. From the states of the atom “decayed” or “not decayed”, it can’t be directly concluded, weather or not the cat is dead or alive. For example, the cat may have deceased by some other reason and may found dead by an observer, even though the atom didn’t decay yet. Superposition is something which happens with observable which you can model in vector spaces and not between any arbitrary variables you may accidentally observe.

[@Godplayzdice]

Observer also has two choices - to look or not to look. Observer's wave function also collapses then?