The No Cloning Theorem
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it as an accessible, intuitive explanation of why perfect quantum cloning is impossible and why linearity is the key ingredient.
Recommended by 3 people across 3 different months, 2017 to 2020.
What it is
A ten-minute minutephysics explainer that walks through the full proof of the quantum No-Cloning Theorem without heavy math, using Schr\u00f6dinger's cat in place of a qubit. It relies on the linearity of quantum (unitary) transformations and tensor products of systems, and notes that teleportation is still allowed.
What people said
Recommends Tausif Hossain · 2017-06 · Physics Stack Exchange · on “Teleportation and the observers effect”
This is an interesting question. But according to quantum mechanics it is possible although difficult. By careful tricks and procedures this can be done but the original being would be destroyed. And so I recommend you watch these videos which explains this( especially video 3): Quantum Teleportation [LINK] Cloning [this video] How Teleportation works [LINK]
Recommends Emilio Pisanty · 2018-07 · Physics Stack Exchange · on “What is the basis of the use of Hermitian matrices as quantum gates?”
This isn't true: all quantum gates must be Hermitian. Instead, quantum gates must be (i) unitary and, as a pre-requisite, (ii) linear . The no-cloning theorem rests exclusively on the latter, via mechanisms that are explained in depth e.g. in the Minute Physics explainer on the No-Cloning Theorem [this video] . The linearity of quantum gates itself is a core postulate of quantum mechanics, and we know of no deeper principle from which you can explain it. In fact, the principle that quantum gates must be linear is the correct understanding of the principle that matter has a wave nature. We can't really say why that's the case; we just know that it happens.
Recommends PNS · 2020-05 · Physics Stack Exchange · on “Is it possible to clone physical objects?”
No. There is an entire theorem in quantum mechanics which forbids cloning of quantum particles, called the No cloning theorem [LINK] . And also, you cannot measure each and every property or quantum state of a particle precisely. So, no, perfect cloning is not possible. If you want a baseline level explanation of this theorem, this Minutephysics video [this video] is a nice starting point.
Cites mcchucklezz · 2017-12 · Physics Stack Exchange · on “Could the cloning paradox be circumvented by inaccuracy?”
In this video [this video] by minutephysics, the idea of cloning two systems or structures perfectly is gone over and supposedly disproved. However, couldn't the argument be made that a perfect clone is unecessary, and that a functional clone is possible? e.g. I have a kilogram of copper, and the level of precision required to replicate that kilo of copper is very low. Would the cloning of functional copies be possible?