HN Theater @HNTheaterMonth

What you are describing is a "hidden variable" theory. They are disproved by the experiments of the Bell's inequality. It's more weird, much more weird.

Let's continue with your experiment about the pair of red or green socks. If you and your friend measure if they are red-or-green, both will get the same results. This can be explained with a classical theory. Nobody disagree with that.

The weird part is that you can measure if they are 50%red and 50%green! Can I call it yellow? This makes no sense with classical socks and colors, but it makes sense for quantum particles and other properties.

But there are two ways to combine 50%red and 50%green, the technical notation is (R+G)/sqrt(2) and (R-G)/sqrt(2), one with a plus and one with a minus. Can I call them good-yellow and bad-yellow? Or you prefer yellow and blue? In one of the experiments, red means vertical and green horizontal, so one of the combinations is a 45° diagonal like this / and the other is a 45° diagonal like this \. You don't need fancy equipment to measure the combinations, it's just a polarizer rotated 45°. Can I call them yellow and backyelow? I prefer good-yellow and bad-yellow because it's more clear that something weird is happening.

If you measure red-or-green and your friends measures good-yellow-or-bad-yellow, then the results will not be correlated. If you got "red", your friend has a 50% probability of getting good-yellow and a 50% probability of getting bad-yellow. There is nothing to explain here.

If you and your friend measure if they are good-yello or bad-yellow, both will get again the same results. This can be again explained with a hidden variable theory. Both socks "know" what to say if they are asked if they are red-or-green and what to say if they are asked if the are good-yellow-or-bad-yellow.

It get's more interesting when you pick more combinations, like 90%red and 10%green. Can I all it orange? And you can pick 10%red and 90%green. Can I call it lemon? If you measure red-or-green and your friends measures orange-or-lemon, then if you got red, your friend will get orange 90% of the time.

And there are good-orange, bad-orange, good-lemmon and bad-lemmon. And there are many more shades of orange-yellow-lemon. But this is getting too long.

You can have very smart socks that know what to answer for every possible combination of colors. So if you and your friend ask for the same color, whatever it is, both get the same result.

The problem is when you and your friend measure many times using the correct shades of orange and lemon. So the results don't agree 0% neither 100%. You can count how many times you get each combination of results, like (red-vs-dark-orange, or green-vs-bright-yellow), and then add and subtract some of them.

If you assume the socks can's communicate with the other socks before answering, then the result of the calculation is smaller then some number. But in the experiments disagree.

There are some videos with all of this, with a better and longer explanation by MinutePhysics and 3Blue1Brown https://www.youtube.com/watch?v=zcqZHYo7ONs and https://www.youtube.com/watch?v=MzRCDLre1b4&t=0s

⬐ d0mine

It reminds me boxes with 3 green/red lights from the workshop "Quantum Mechanical View of Reality" by Richard Feynman https://youtu.be/ZcpwnozMh2U?t=18m20s

(there is a statement that 3 is the minimum, 2 lights won't work)

> I have a lot of trouble imagining any experiment which could completely rule out every other influencing factor

It's called Bell's theorem and it can even be tested at home[4]. There are no local hidden variables in quantum mechanics.[1][2][3]

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

2. https://en.wikipedia.org/wiki/EPR_paradox

3. https://en.wikipedia.org/wiki/Hidden-variable_theory

4a. https://www.youtube.com/watch?v=zcqZHYo7ONs

4b. https://www.youtube.com/watch?v=MzRCDLre1b4

⬐ lulantivaxxers

Thanks for this, hidden variable theories are very seductive but Bell's Theorem is definitive.

⬐ naasking

It's definitive that you have to give up locality (Bohmian mechanics), counterfactual definiteness (Copenhagen and others), or statistical independence (Superdeterminism). It's not definitive at all about local hidden variables.

⬐ guerrilla

> It's not definitive at all about local hidden variables.

What?

> To date, Bell tests have found that the hypothesis of local hidden variables is inconsistent with the way that physical systems do, in fact, behave.

⬐ naasking

Bell's theorem assumes statistical independence in its proof that local hidden variables can't reproduce QM. Superdeterminism violates statistical independence, therefore Bell's theorem does not rule out a superdeterministic local hidden variables theory, like this one:

https://arxiv.org/abs/2010.01327v5

⬐ guerrilla

Oh, thank you. I've been meaning to check her blog on this.

another great explanation here https://www.youtube.com/watch?v=MzRCDLre1b4 also from 2017

I found these two videos very helpful in understanding the quantum nature of light after being stuck in the same spot: https://www.youtube.com/watch?v=zcqZHYo7ONs https://www.youtube.com/watch?v=MzRCDLre1b4 (Watch those in order, because they're a collaboration between two YouTubers)

Minute Physics and 3brown1blue did a two part collab that simplifies some of it down to a counting problem that'd be suitable for grade school.

https://www.youtube.com/watch?v=zcqZHYo7ONs

https://www.youtube.com/watch?v=MzRCDLre1b4

⬐ lpellis

I have seen the example with the polarized lenses in a few places, but they dont explain why (imo) the simplest explanation does not apply. Namely that the lens itself might disturb the phase of the light, which would then mean it can pass through the next lens.

⬐ wwarner

The idea is that polarization is only one of many places where the effect is observed.

⬐ sooheon

But if you take away the third lens, there is no light of any polarization. How is it that by adding a filter, you create light where there was none?

⬐ lpellis

Only if you take away the middle lens, not the third.

Here's what I would have thought happens: After the first lens, you get polarized light, 90deg offset from the last lens, so no light passes. Then you introduce a 3rd lens in the middle, 45deg offset. This could alter the polarization (maybe it widens the band, or introduce some greater variance, shifts it who knows), and this is why now some light will pass through number 3. No need to create any light

⬐ sooheon

If it is true that placing the 45 degree lens third or first does not show the same effect, it is much less astonishing.

⬐ seycombi

Complementary video (Bell's Theorem) on MinutePhysics: https://www.youtube.com/watch?v=zcqZHYo7ONs