How to Teleport Schrödinger's Cat



there are basically three kinds of teleportation the kind where the thing you want to teleport is somehow instantly move from one location to another perhaps by a loophole in the fabric of space-time or magic or something the kind where you disassemble the object and send the pieces to the faraway location to be reassembled and the kind where you scan the object in one place and just transmit the instructions for how to reassemble it somewhere else using different molecules and atoms this last kind of teleportation kind of sounds like cloning since couldn't you just scan the object and send instructions to reassemble a copy somewhere else without destroying the original but no quantum mechanics prohibits exact copying of arbitrary objects so any method of teleportation governed by the physics in our universe will somehow alter or destroy the original object which is kind of nice because it bypasses those soul-searching paradox inducing questions about which is the real view the teleported you or the stuff that was left behind no cloning implies the teleported one is unequivocally the real one this isn't just science fiction well human teleportation is but physicists have successfully used this method to teleport photons of light electrons even calcium atoms in this video I'm going to show you exactly how quantum teleportation works in the hopes of giving you a clearer picture of what it can do and what it can't physicists usually teleport small quantum things in a superposition of several states like an electron that's in a state of spin up and spin down or whatever but we're going to use Schrodinger's cat in a superposition of alive and dead until you look inside the box in which case the state collapses to just one of the two options alive or dead the math is the same but come on this is the Internet before we get into the details and I promise there will be many we need to talk for a second about quantum entanglement because it's the transmission mechanism that makes teleportation possible quantum particles as you may have heard can be in multiple different states of existence at once like spin up and spin down or alive and dead or exploded and not exploded or if you have multiple particles they can be in various different combinations of their possible states of existence like heads and tails plus heads and heads saying two or more particles are entangled just means that the states of the particles aren't independent of each other for example if the Gunpowder explodes shorteners cat will be dead and if the gunpowder doesn't explode shouting errs cat will be alive but the powder can't be unexploded while killing the cat and vice versa so the alive or dead state of existence of the cat is entangled with the exploded or not state of existence of the gunpowder or two atoms can be entangled if the outer electron in one is always orbiting to the left while the other is orbiting to the right or vice versa so even though either atom could be in either state they're always opposite and if we know the state of one we know the state of the other in general if you have a set of fully entangled particles you only need to know the states of half of them to be able to infer the states of the other half that's not the case with heads and tails plus heads and heads if the first coin turns out to be heads we still don't know what the second coin is so they're not entangled okay so the reason we started talking about entangled pairs of objects is that since entanglement can be maintained over arbitrarily long distances entangled particles are the transmission mechanism for teleportation send a pair of entangled objects to two separate locations and one of them is kind of like a mold or scanner and imprints the state of the thing we want to teleport the other object because it's entangled with first ends up as a kind of negative of that imprinted state that's basically it but to see how teleportation works in detail let's send Schrodinger's cat to the moon remember Schrodinger's cat hidden in its box has some probability of being alive and some probability of being dead so it's in a quantum superposition of a times alive plus B times dead where we have no idea what the probabilities actually are in order to teleport the cat's state of existence a alive and be dead to the moon we need an entangled pair of particles one here and one on the moon like an entangled pair of fleas each hidden in its own box where one flea is dead and one is alive but we don't know which one so they're in a superposition of earth flea is alive and a moon flea is dead plus earth flea is dead and moon flea is alive maybe we'll call them Schrodinger's fleas and we're going to teleport the cat state of existence to the flea on the moon by putting the earth flea and the cat together in the same box entangling them in a particular way and thus teleporting the cat's state to the moon flea I know it sounds crazy but if you replace cats and fleas with electrons or photons or atoms this is exactly what happens here's how teleportation works the cat's initial life-or-death state is a times alive plus B times dead the entangled pair of fleas are initially in a state of earth flea alive moon flea dead plus earth flea dead moon flea alive in equal proportions so the cat together with the fleas is a times cat alive plus B times cat dead times earth flea alive times moon flea dead plus earth flea dead times moon flea alive this seems like a complicated situation but it just means that if we were to look inside the boxes with probability a we'd see the cat alive and exactly one of the fleas dead either the moon flea or the earthly and with probability B we'd see the cat dead and still exactly one of the fleas dead either the moon flea or the earth flea no teleportation just a cat and some fleas entangled with each other but not with the cat so we won't look in the boxes like that to start the teleportation process we need to get the cat also partially entangled with the fleas and to do that we'll put the cat and the earth flea inside the same box and look inside it in a sneaky indirect way what I mean by indirect is that we can't just open it up to see whether the cat and earth flea are each alive or dead since that would entirely collapse the superposition either killing or saving the cat and flee and resulting in a failed teleportation instead we need a more subtle measurement that only partially collapses the superposition and tells us just a little bit about both of them but not everything for example we could ask are they the same which would mean that either both cat and earth flea are alive or both are dead but we don't know which or we could ask is only one of them dead that is one is dead while the other is alive but we don't know which one or at least one is dead which would mean either the cat is alive and the flea is dead or the cat is dead and the flea is alive or both are dead but we don't know which or the cat is not dead alone which would mean either the cat is a with the flea either alive or dead or the cat's dead and the flea is dead too but again we don't know which you'll notice that none of these for questions on its own allows us to determine the full life or death situation of the cat and its earthbound flea at least one is dead tells us something about the cat and earth flea but not everything the four questions taken together however are an alternative way of fully specifying the cat and flea situation that we can use instead of dead and dead alive and alive alive and dead and dead and alive for example if the cat is alive and the flea is dead then we could write that boringly as alive times dead or in our sneaky indirect way as the cat isn't dead alone – the cat and the flea are the same you can check to see that it works out the sneaky way to write cat and flea are both alive is well you could pause the video now to try to figure out on your own or wait for me to tell you it's they're both the same plus they're both different – at least one is dead and the sneaky way to write cat is dead and flea is alive is they're both the same plus they're both different – the cat isn't dead alone and the sneaky way – right they're both dead is at least one is dead – only one is dead the point of all this sneaky indirect questioning remember is to bring the cat into the entanglement with the fleas which is what actually teleports the cat's life-or-death situation to the moon flee to see why this works we'll have to write out the full state of the cat and both fleas and remember from before it was a times cat alive plus B times cat dead all times worth flee alive time smoothly dead plus earthly dead time moon flee alive and then rewrite this in terms of the sneaky questions there's going to be a bit of algebra and distributing and such going on in the next little bit but this is the part where the teleportation actually happens so it's worth the effort first we will write out the full state of the cat and both fleas so that we don't have any parentheses that means distributing through the a times cat alive plus B times cat dead giving us a times cat alive times earth flea alive times moon flea dead plus a times cat alive times earth flea dead times moon flea alive plus B time's cat dead times earth flee alive times moon flee dead plus B times cat dead times earth flee dead times moon flee alive it's a mouthful but we're just getting started now we need to entangle the cat and the earth flee so we're going to rewrite the cat and earth flee parts in terms of our sneaky indirect questions remember where instead of cat alive times earth flee alive we have both the same plus exactly one alive – at least one alive and instead of cat alive times earth flee dead we have the cat isn't dead alone – both the same and instead of cat dead times earth flee alive we have both the same plus exactly one alive – the cat isn't dead alone and instead of cat dead times earth flee dead we have at least one is dead – exactly one is dead if we now sort through this big mess and to group all the different pieces together by the indirect questions we find that we have four options either at least one of cat and earth flea is alive while the moon flea is in a superposition of alive and dead or exactly one of cat and earth flea is alive while the moon fleas in a superposition of alive and dead or both are the same while the moon flea is in a superposition of alive and dead or the cat isn't dead alone while the moon flea is in a superposition of alive and dead notice a pattern by reframing the situation in terms of the indirect questions we've now put the moon flea which started off entangled to the earth flea into one of several possible superpositions of alive and dead each of which looks kind of like the original cat superposition a alive and be dead there's one last step to complete the teleportation now finally at the end we actually look in directly into the cat and earth flea box to collapse their combined wavefunction – just one of the possible sneaky options like maybe we look in indirectly and find out that the cat isn't dead alone then we know that the moon flea is in a superposition of a alive – be dead which is almost exactly the same as the cat's original a alive plus B dead state all we need to do is switch B and minus B which can be done by somebody on the moon after we beam them the message about the cat not being dead alone and then the moon flea is in the state that the cat was in originally successful teleportation if instead the cat and earth flea had been in the at least one is dead state then the moon flea would be B times alive minus a times dead and we could tell the person on the moon to just swap B for a and minus a for B and the moon flea would be in the state the cat was originally another successful teleportation and there are simple swapping rules for each of the other possible scenarios so we can guarantee that after the dust settles and all is said and done the cat's state of existence will be teleported to the moon at this point you may be wondering about two things first how is this teleportation if we didn't actually send a cat to the moon we just sent the life or death State to the cat was in to a flea on the moon well I used fleas so the math would be easier to follow but if instead of fleas we used two piles of particles that you could in principle make a cat out of and if we viewed our whole cat as just a particular configuration of a pile of particles which is ultimately what it is then by quantum teleporting the state of the pile that looks like a cat to the blank canvas pile of particles on the moon we would indeed end up with a cat on the moon that is literally the same cat we started with while the particles that were originally the cat on earth would now be what would they be that's the second thing you might be wondering what happens to the original cat on the earth well in the case of teleporting a pile of particles that look like a cat I mean are a cat after the teleportation the pile of particles that originally was in the state of a cat will be in the most mixed-up state possible for those particles almost as if it had been put through a blender and not at all like a cat to illustrate this a little more clearly if instead of a real cat we just teleported the word cat encoded as a quantum state after the teleportation the cat on earth would no longer be ca tea but would in fact be in a superposition of every single possible three-letter word all of them equally likely that is it would be entirely jumbled and nothing like the original CA T whatsoever and there would be absolutely no confusion about which one the original cat or the teleported cat is the real cat I mean it's obvious only one of them is a cat of course physicists haven't succeeded in teleporting whole cats yet or even for that matter the word cat it's very very hard to make entangled pairs of big piles of particles and then have them stay in tangled long enough to take one to the moon so far only simple quantum states like those of a single photon or electron have been teleported and only as far as about a hundred kilometers so teleportation teleportation is a long way off if only we had some way we could get there faster

38 thoughts on “How to Teleport Schrödinger's Cat

  1. That was a very very accurate explanation of how quantum teleportation works! Even with the "questions" analogy. Bien jugado, Henry.
    Although I was expecting to listen something: because the teleportation can't be completly perform if the Earth's scientist doesn't tell the moon's scientist the answer of the question he asks to the original cat, faster than light quantum teleportation is impossible. He needs to send to the other guy that answer in the traditional way.

  2. is this reversible ? or are the particles used -up and cannot be re-used in making of a cat… and flee..or something else.. If particles of the original object are not re-usable then we will have Quantum waste .. In such case as there is a limit of how many particles exist at a given location… There will be an upper limit to teleportation.. That would not be bad because with teleportation you can forget about customs… people secretly and illegally entangling Huawei phones, plastic waste , lakes for drinking water , all sorts of illegal substances, nuclear weapons , gold, oil, counterfeit items, rolex watches..

  3. 12:30 , yeah I got everything you said, but how do you teleport it . You explained what you need to teleport , but didn’t explain how to teleport.
    Edit: 13:56 I’m trying to do that . I don’t care if I get made fun of or not

  4. Isn’t there chance (even if it’s in the trillions that the original cat can be put back together. It’s in a super position o every 3 letter word, does that that exclude the super poi’s it ion of CAT itself like some rule it’s already being use by the other entangled partical

  5. So its like Star Trek. You're an extra wearing a red shirt on an away mission. You aren't dead, but you really are.

  6. Does this mean the magic really happens to the particles left behind? Are those particles left in a state of unknown forever or whatever they are left as? Thanks for making it fun to at least try to understand!

  7. I only understand is the left hand side is earth and the right hand side is moon. That's all!

  8. That was awesome! I actually followed it, and I've never understood teleportation before. Thank you! 😀

  9. I think this is the only channel where "flea", "moon" and "quantum superposition" can be placed in the same sentence in a way that seems totally normal

  10. pls help me anyone i am from 2041 and i suddenly landed in a world which is unfamiliar to me please help and when i ask anyone which year is it they tell that it is 2019 pls help me i am stuck here

  11. I guess that third teleportation will use qbits.

    A scanner scans the object. It will make a copy of it in qbits. Due to the laws of quantum mechanics, the scanned object is no longer you.(maybe because the molecular structure of yours collapsed after the scan?)
    You are now a qbit(or qbits.)
    When recreating you, the qbits will collapse and will default to a random value again.
    But in return, you are now back in a flesh body.

    (Maybe that would happen)

  12. A cat and two fleas walk into a bar. The bartender, who is the creator of minutephysics, decides to send one flea to the moon to try and teleport the cat to the moon while trying to make a 14 minute video at the same time while managing to do all that within microseconds. But wait! This is Schrodinger's cat, which means that by simply looking at the cat minutephysics has destroyed it. Trying to fix his mistake, he keeps the two entangled flies in a jar, keeping them entangled for as long as possible while he speed-watches his previous videos about time travel. He builds a time machine, and accidentally kills his grandfather. Now what to do? He watches his video on the Grandfather's paradox to resolve the situation, but while he was doing so 3blue1brown captured him and forced him to work in the attic to upload a video on Feynman's Lost Lecture, all the while stealing the time machine to do things on his own. Eventually minutephysics escaped but he has very little time before the fleas become useless. So he tries to learn relativity to slow down time, but since he is constant pressure to upload videos he had to upload an entire series. With his now-useless cat in his hand and very little fuel in his rocket, he needs to find a way to get energy from a cat, which he researches, finding that Norway goes through 150 billion cats a year. He patents a new solution and throws the cat in a black hole. He also throws the fleas, in, too, since they have long since decohered and lost their special entanglement properties. Arriving back to earth with seconds of fuel to spare, he ditches the idea of doing it in real life and makes this absolutely wonderful video.

    Oh, and I'm definitely not extending your watch time. Go check out his channel!

  13. This explanation was made more confusing by the cat and flea analogies. My god! Just talk about the state of particles!

  14. I may be asking a really dumb question but as you said, the word "CAT" after the teleportation could become any possible three-letter word combination, however, there is still a chance that it stays as "CAT" and so would you have created that supposedly impossible clone you mentioned, right?

  15. ° _ °

    So,
    If i get a cat, in a box, and then, i put a flee in.
    I go to a restaurant, with a flee in a box.
    I ask someone to put lasagne in the box, and then
    I go back to my home, and, i.. shake the box…
    I, will.. get my lasagne back home ?

  16. Oh wow using the fact that certain states of particles are influenced by observation to make them act the way you want, that's sneaky.

  17. Thank you you just helped me figure out the perfect power to give my character in the book I’m writing

  18. Yea this would have probably been easier to understand if you just used quarks and positive or negative states.

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