Consciousness Videos

The No Cloning Theorem



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Why you can’t clone Schrödinger’s cat: this video presents the full proof of the “No Cloning” Theorem in Quantum Mechanics – without any fancy math! (stereotypical qubit has been replaced with Schrödinger’s cat).

The full proof relies on the linearity of quantum (aka unitary) transformations, and the tensor product of multiple systems, to show that perfect cloning is impossible (though teleportation is allowed)

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REFERENCES:

The No-Cloning Theorem: https://en.wikipedia.org/wiki/No-cloning_theorem

MinutePhysics on Schrödinger’s Cat: https://www.youtube.com/watch?v=IOYyCHGWJq4

Original No-Cloning Paper by Wootters and Zurech: http://www.nature.com/nature/journal/v299/n5886/abs/299802a0.html

Original “Beyond No-Cloning” (ie, no-cloning workarounds) paper by Buzek & Hillery: https://arxiv.org/abs/quant-ph/9607018

Optimal Quantum Cloning paper: https://arxiv.org/abs/quant-ph/9801009

Optimal Quantum Cloning paper II: https://arxiv.org/abs/quant-ph/9910048

Quantum Cloning: https://en.wikipedia.org/wiki/Quantum_cloning

The History of Schrödinger’s (& Einstein’s) Cat: http://nautil.us/issue/41/selection/how-einstein-and-schrdinger-conspired-to-kill-a-cat

The Stability of Black Powder (from the Civil War!): http://www.jpyro.com/wp-content/uploads/2012/08/Kos-806-806.pdf

Proof by contradiction: http://www.personal.kent.edu/~rmuhamma/Philosophy/Logic/ProofTheory/proof_by_contradictionExamples.htm

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28 thoughts on “The No Cloning Theorem
  1. Hello everyone! I am back from a 2+year comment hiatus and excited to say hi! (my account wasn't linked with any google+ account, so I couldn't comment on YouTube from the MinutePhysics account for the last 2-3 years; google finally gave up on google+ enough that now I can comment on YouTube again!!)

  2. I love the step by step logic, however, I believe there is an invalid assumption in this video that led to the wrong conclusion.
    The assumption was made at 2:33 that multiple particles, or whatever, are the product of their components. While this may be true mathematically for vectors, it is not totally applicable to everything in the manner that it is suggested. For example, this works mathematically: |5> = |2> x |3> but notice that optically speaking, the number 5 looks very different from either the 2 or the 3 that produces it. Likewise, multiplying a |barrel> with a |cat> might produce something totally unexpected, like a bowl of spaghetti rather than a barrel next to a cat.
    I think, it is more likely the case that the collection of a barrel and a cat should be represented as the sum of it's parts, not the product. Therefore, the product sign ("x") in the equation at 5:12 should be a plus sign ("+") instead, and in that case, the math does work out, and cloning can exist.
    However, that being said, unless we can figure out how to control everything in the universe that might have an effect on something, we will likely never be able to clone it perfectly. Even if we could clone something for an instant, the two things would cease to be the same in the next instant because forces of the universe will be different at two points in space.

  3. this is how we can make cloning:make a videogame with a clone machine then make a teleporter in the same game make a teleport thing in reality put the videogame clone machine in the videogame teleporter. Use both teleporters to travel the clone machine in reality and if that does not work then just make a portall to another universe and ask the other universe for a clone machine

  4. My favorite proof by contradiction is infinite prime numbers:
    -Assume there are finite amount of prime numbers,
    -Multiply all of them and add 1
    -The new number can't be divided by any prime numbers, but isn't equal to 1.
    Thus there is always a bigger prime number!

  5. Wait, if perfect cloning is impossible, and without it we can't copy over consciousness, how does teleportation work without creating a new being in a similar body? Wait, wtf did I just type

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