Comments by "Sasha S" (@sashas3362) on "Anastasi In Tech" channel.

@boozlightyear "Quantum theory" as you call it, or everett-wheeler interpretation to be more specific, is proven by quantum computers because they require the existence of alternate universes to surpass the abilities of classical computers. They compute in entangled alternate universes to achieve "quantum supremacy" which has already been demonstrated.
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@awillingham Not necessarily. There are ways of overcoming noise and/or even making use of it. If you have a lot of redundancy meaning the same qubit duplicated many times then it would be hard for noise to damage the signal. CD's use that method (combined with error correction) to prevent data loss due to scratches. You know what I mean?
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@awillingham Perhaps you are right. I am no expert on that topic. I've read measuring a qubit tends to add noise to the system which tends to make quantum computing impossible but only if there is only one copy of each qubit. If you instead have millions of qubits entagled into the same state via (macroscopic?) quantum coherence then you can measure only one of the qubits and this will add only a negligible amount of noise by decohering one qubit out of the millions. This was presented as a way to possibly defeat quantum encryption. You see? I don't remember all the details bit the idea was you can "clone" a signal photon using an optical amplifier or something like that so that you have a duplicate an eavesdropper can measure while the other photon continues on it's way to the intended recipient. If the eavesdropper then clones the cloned photon a million times and then only measures one of those million clones then the coherence of the clones will overpower the decoherence caused by the decoherence of the one photon which is measured and keep them cohered into the same state as the original photon received by the intended recipient. You see? I read this about 10 years ago maybe even 15 years ago.
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@mennoknol8693 I don't believe cloning a photon collapses it's wave function. It's wave function isn't collapsed until it's measured. You can clone a photon without measuring it.
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@mennoknol8693 A single photon is cloned in a laser. How many times? A potentially unlimited number of times. It depends on the material. I'd say millions of times is not an unreasonable guess. Possibly billions or trillions of times.
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@mennoknol8693 Yeah, actually they ARE cloned. The no-cloning theorem of the pauli exclusion principle only applies to fermions not bosons such as photons which allow for the creation of bose-einstein condensates which allows for macroscopic quantum coherence to be observed. Look into macroscopic quantum coherence and you will find that is where many particles effectively become one particle through entanglement or coherence. So, coherence is a form of entanglement. Not the same form of entanglement where if one particle is spin up then you know by default the other is spin down but rather if one is spin up you know the other is also spin up because they are the same (or "coherent"). In a laser, when a photon passes through the lasing medium, which acts as an optical amplifier, it induces stimulated emission which is how you clone a photon (according to the theory of laser function based on stimulated emission...which is only one of two theories of laser function I know of but I won't get into the other because it isn't relevant to this discussion).
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@mennoknol8693 I see your point about how measuring only one of a million cloned photons will cause the waveunction of all the cloned photons to collapse. Good point. I didn't write the article and can't find it anywhere now (it seems to be hidden now for reasons which should be obvious if it works) so can't say for sure but maybe one would actually need to measure all of them to collapse their wavefunctions. It may be the unmeasured photons each generate "noise" with much of that "noise" existing in the form the original signal. If you have more unmeasured photons than measured photons this "noise" from the unmeasured photons may drown out the noise from the one measured photon. Keep in mind that the noise generated from the measured clone photon comes from it becoming entangled with the measurement apparatus. When that happens it becomes decohered and is no longer entangled with the other cloned photons after that. That is why we say it's entanglement gets destroyed by noise. That one clone photon's entanglement does get destroyed when measured by an eavesdropper but when measured it won't alter the properties of the original(?) photon received by the intended recipient because the original signal is reinforced by the "noise" from all the uneasured photons which is identical to and reinforces the original signal encoded in the original photon received by the intended recipient. You see?
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@mennoknol8693 According to bohmian mechanics there is no actual superposition. From our pov there is uncertainty. But no actual superposition.
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@mennoknol8693 Also according to bohmian mechanics not only is there no actual superposition but there is also no actual collapse of the wavefunction or superpositions. The system has a definite state albeit a state unknown to us until measurement.
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