What can Schrödinger’s cat teach us about quantum mechanics? – Josh Samani
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What can Schrödinger’s cat teach us about quantum mechanics? – Josh Samani


Consider throwing a ball
straight into the air. Can you predict the motion
of the ball after it leaves your hand? Sure, that’s easy. The ball will move upward
until it gets to some highest point, then it will come back down
and land in your hand again. Of course, that’s what happens, and you know this because you have
witnessed events like this countless times. You’ve been observing the physics
of everyday phenomena your entire life. But suppose we explore a question
about the physics of atoms, like what does the motion of an electron around the nucleus of a
hydrogen atom look like? Could we answer that question based on
our experience with everyday physics? Definietly not. Why? Because the physics that governs the
behavior of systems at such small scales is much different than the physics
of the macroscopic objects you see around you all the time. The everyday world you know and love behaves according to the laws
of classical mechanics. But systems on the scale of atoms behave according to the laws
of quantum mechanics. This quantum world turns out to be
a very strange place. An illustration of quantum strangeness
is given by a famous thought experiment: Schrödinger’s cat. A physicist, who doesn’t particularly
like cats, puts a cat in a box, along with a bomb that has a 50% chance
of blowing up after the lid is closed. Until we reopen the lid,
there is no way of knowing whether the bomb exploded or not, and thus, no way of knowing
if the cat is alive or dead. In quantum physics,
we could say that before our observation the cat was in a superposition state. It was neither alive nor dead but
rather in a mixture of both possibilities, with a 50% chance for each. The same sort of thing happens
to physical systems at quantum scales, like an electron orbiting
in a hydrogen atom. The electron isn’t really orbiting at all. It’s sort of everywhere in space,
all at once, with more of a probability of being
at some places than others, and it’s only after
we measure its position that we can pinpoint where it is
at that moment. A lot like how we didn’t know
whether the cat was alive or dead until we opened the box. This brings us to the strange
and beautiful phenomenon of quantum entanglement. Suppose that instead of one cat in a box,
we have two cats in two different boxes. If we repeat the Schrödinger’s cat experiment
with this pair of cats, the outcome of the experiment
can be one of four possibilities. Either both cats will be alive,
or both will be dead, or one will be alive
and the other dead, or vice versa. The system of both cats
is again in a superposition state, with each outcome having a 25% chance
rather than 50%. But here’s the cool thing: quantum mechanics tells us
it’s possible to erase the both cats alive and both cats dead
outcomes from the superposition state. In other words,
there can be a two cat system, such that the outcome will always be
one cat alive and the other cat dead. The technical term for this is that the
states of the cats are entangled. But there’s something truly mindblowing
about quantum entanglement. If you prepare the system of two cats
in boxes in this entangled state, then move the boxes to opposite
ends of the universe, the outcome of the experiment
will still always be the same. One cat will always come out alive,
and the other cat will always end up dead, even though which particular cat
lives or dies is completely undetermined before we measure the outcome. How is this possible? How is it that the states of cats
on opposite sides of the universe can be entangled in this way? They’re too far away to communicate
with each other in time, so how do the two bombs always
conspire such that one blows up and the other doesn’t? You might be thinking, “This is just some theoretical
mumbo jumbo. This sort of thing can’t happen
in the real world.” But it turns out that quantum entanglement has been confirmed in
real world lab experiments. Two subatomic particles entangled
in a superposition state, where if one spins one way
then the other must spin the other way, will do just that,
even when there’s no way for information to pass
from one particle to the other indicating which way to spin
to obey the rules of entanglement. It’s not surprising then that
entanglement is at the core of quantum information science, a growing field studying how to use
the laws of the strange quantum world in our macroscopic world, like in quantum cryptography, so spies
can send secure messages to each other, or quantum computing,
for cracking secret codes. Everyday physics may start to look
a bit more like the strange quantum world. Quantum teleportation
may even progress so far, that one day your cat will
escape to a safer galaxy, where there are no physicists
and no boxes.

About James Carlton

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100 thoughts on “What can Schrödinger’s cat teach us about quantum mechanics? – Josh Samani

  1. I don't understand why we can erase both cats alive and both cats dead from the "superposition state". Can someone explain?

  2. What goes on in the brain at a quantum particle scale? Is there any quantum entanglement going on in the brain? Is that how esp works?

    My favorite position is Super Position. What's yours?

  3. Just a minor correction:
    Schrodinger envisioned a flask of poison and a radioactive source placed in a sealed box.
    Not a bomb.

  4. Superb explanation. Thank you. I really fed up telling to QE speakers, it was not Einstein’s prediction. Because he has never understood QM but he said spooky things for QM. This is not a term of a scientist use for serious science but only a comedian can use that kind of terms for serious science.

  5. Though I haven't started learning any of the quantum mechanics equations or anything I find it very easy to understand and interpret most of the ideas of quantum mechanics

  6. Schrödinger took his cat to the vet, after examining the cat the vet said….."Well Mr Schrödinger we've got good news & bad news"

  7. Just a shame , just a shame modern science never takes into account the required prescence of biological observation in any of these cases , these laws only really make sense if there is a observer present

  8. What is superposition state?…. and how can the two cat be either dead or dead ..? Why cant both of them be alive or dead according to quantum enlargement !!!? Something quiet confusing??

  9. I didn't get any of this. I'm not smart enough.

    So…now the one cat turned into two cats because of the entanglement?

    Greets from the Philippines 🇵🇭

  10. Time does not have a beginning nor end. When you talk about the existence of Time you are making reference to differentiated Time, not about the Singularity of time, as in before the Big Bang. Time exists only as the Reality of the moment, the here and now.

  11. If A and B are entangled (showing opposite results)
    And C n D are entangled
    Would quantum entanglement show that
    A is Entangled with both C and D
    😶😶

  12. So if I put a bomb that has a 100% chance of blowing up, that cat would be dead and alive and I break reality!!!

  13. So two atoms acts on the same pattern despite the distance, but the question is WHICH two atoms? Any random two atoms?

  14. Quantum physics is also like everyday physics, pauli exclusion principle is collision, pilot waves which were said to be like quantum particles are stuck in the wave, causing inertia, as the droplet slides down the wave, and things can move because there is a chance of it sliding away from the center, which is why things stay in motion if not slowed down by friction,

  15. Everyone who wants to make some sense of quantum mechanics must know
    from the beginning that (a) physicists do not know yet why it works; (b)
    there are DIFFERENT interpretations of it – so whoever tells you "I
    KNOW" – is a lair. @t

  16. Everyone who wants to make some sense of quantum mechanics must know
    from the beginning that (a) physicists do not know yet why it works; (b)
    there are DIFFERENT interpretations of it – so whoever tells you "I
    KNOW" – is a lair. @t

  17. Everyone who wants to make some sense of quantum mechanics must know
    from the beginning that (a) physicists do not know yet why it works; (b)
    there are DIFFERENT interpretations of it – so whoever tells you "I
    KNOW" – is a lair. @t

  18. This is the best rendition (examples ; explanation) of super-position and entanglement I have ever heard Very well explained …So well… That your almost giving away the whole secret And I do mean this seriously !!!

  19. Or you could just simply flip a coin. Before you look at it, it exists as heads and tails. Why do they OVER AND OVER.AND OVER AND OVER long windedly explain this sick, dead cat in a box example?

  20. so, it means when I was in my mothers womb I was in superposition of dead and living, until doctors took the observation.

  21. How quantum mechanics erase the two cats alive and two cats dead outcome?
    Please, can someone tell me? I searched Google, but no matching result. 🙁

  22. Didn't get how could the possibilities of the 2 cats alive or both dead can be ruled out. Also is it reason behind two clocks with pendulums synchronise each other some time later

  23. What do you do if you have 3 cats in 3 boxed and put 1 bomb in each..

    every time 2 cats are both dead or alive so entelgagement doesn’t work for these cats

  24. if they are using bomb then if it explodes doesn't that will create a big noise so without opening also we will come to know the cat is alive or not…….

  25. What if both the boxes were in the part of universe where cat cant surive?..then both the cats will be dead even though there are entangled

  26. The bomb analogy doesn’t work because you’d know the cat was dead if the box blew up before it was opened; has to be silent poisoning.

  27. "How is it that the states of cats on opposite sides of the Universe can be entangled in this way? They're too far away to communicate with each other in time, so how do the two bombs always conspire such that one blows up and the other one doesn't?"

    And the answer is… what? Please explain why does this happen?

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