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n4r9

Also, any kind of instantaneous communication.

Unless the theory of relativity is superseded by something quite radically different.

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High school educated talking here.

Does Quantum Entanglement have any promise for instantaneous communication (theoretically) ?

Nope, you can't pass information through entangled particles. All you know when you measure you particle is that the other one will turn out the same (or is likely to, I forgot the exact details). This does not lend itself to any communication protocol.

https://news.fnal.gov/2020/12/fermilab-and-partners-achieve-....

That's about transmitting qubit-encoded information. It has absolutely nothing, at all, to do with FTL communication. It's a somewhat more elegant solution than USPS for solving the problem of "I have a qubit here, I want to move it over there".

Nope, entangled pairs are basically the following in JS:

    class RawQuantum { 
      value = () => this._hidden ??= Math.random() 
    }

    class EntangledQuantum extends RawQuantum {
      valueA = () => this.value()
      valueB = () => 1 - this.value()
    }

    const {valueA, valueB} = new EntangledQuantum()

You can give valueA to one procedure and valueB to another and know that whenever the _hidden field is observed, the two will have complementary views of the data. But this doesn't give the two procedures any way to communicate, and there's no measurable difference between resolving the _hidden filed now or later.

To elaborate somewhat on the basically, the key difference between this example (and the more common "put a left shoe in one shoebox, a right shoe in another, shuffle, and send each to different people" example) and actual quantum entanglement involves being able to choose from a multi-axis spectrum of different measurements, and the resulting level of correlation precluding the possibility of there being a local hidden variable (the leftness or rightness of the shoe in the box before opening).

That only works if you replace "basically" with "not really". With this code you can't violate Bell's inequalities[1], which is a really important feature of Quantum Mechanics.

[1] https://en.wikipedia.org/wiki/Bell%27s_theorem

For someone who is trying to learn the basics of quantum entanglement, the distinction between local and non-local hidden variables isn't take that essential.

Or make those "hiddens" in the code above globals. Problem solved.

Non-locality seems to be the least favorable way to resolve the Bell inequalities as far as most physicists are concerned. I'm not sure why though. I think they like exotic and unintuitive sounding stuff.

> I think they like exotic and unintuitive sounding stuff.

Exactly the opposite, nonlocality is by far the most exotic resolution here. It means losing existence and uniqueness of solutions to differential equations - i.e., causation.

Could you expand on this, or provide a source? I don't see how physics could yield a pure math result like that.

Other way around. Of course physics has nothing to do with whether a theorem is true or false - but it has everything to do with whether our universe satisfies that theorem's hypotheses.

I'm also struggling to make sense of what you're saying. Non-local measurement outcomes have very little to do with causality. Are you arguing against specific interpretations such as Bohmian mechanics, which require privileged space–time foliations?

>> Exactly the opposite, nonlocality is by far the most exotic resolution here.

I think a multiverse, or anything "spooky at a distance" or the other stuff is exotic. Non-locality does take away our ability to do experiments in isolation I suppose, which is kind of a big problem, but it is limited to certain kinds of experiments and not (seemingly) relevant at larger scales.

The problem is not the distinction between local and non-local hidden variables, but the that the "value" in that code doesn't depend on the measurement being performed.

You can't understand anything about quantum mechanics without knowing that in order to measure a qubit (or anything, really) you need an observable, which is completely missing from that JS code (for a qubit, the observable for a simple projective measurement could be represented by a direction in space).

It probably doesn't, but if it does, it could be used to send messages back in time. Relativity doesn't care how something goes FTL, it's just really clear there's no room for "FTL but not time travel" unless you introduce some odd and unphysical-seeming extra restrictions on the universe.

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