

An Experiment That Changed How We Think About Reality - aatish
http://www.wired.com/2014/01/bells-theorem/

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slacka
How does this relate to Wired's other article on the pilot wave explanation of
quantum mechanics?[1]

"To some researchers, the experiments suggest that quantum objects are as
definite as droplets, and that they too are guided by pilot waves — in this
case, fluid-like undulations in space and time. These arguments have injected
new life into a deterministic (as opposed to probabilistic) theory of the
microscopic world first proposed, and rejected, at the birth of quantum
mechanics."

[1] [http://www.wired.com/2014/06/the-new-quantum-
reality/](http://www.wired.com/2014/06/the-new-quantum-reality/)

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Imerso
It's explained in the footnote of the article. Bell's experiment rules out
local hidden variable theories but it's still possible to formulate non-local
hidden variable theories that work.

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mehwoot
This is very confusing. "But according to quantum mechanics, the answer is
50%". How is this so? The article doesn't mention how quantum mechanics
explains what is going on, just that "classical physics" doesn't.

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aatish
Thanks for pointing that you. My goal was to point out an empirical
observation that can't be explained by a local hidden variables theory. You're
right that I didn't explain how quantum mechanics predicts the same result,
because that's tricky to do in the scope of such an article.

Here's a little more on that: One way you could do this experiment is to
create 2 entangled electrons. Measuring the spin of an electron in the x, y,or
z direction corresponds to the 3 doors on the box. Spin in a given direction
is a binary variable for an electron (up or down) so that corresponds to the
color of the light in each door (red or green).

Since the electrons are entangled, if you measure the spin of one of them in
the x direction (say), then this also constitutes a measurement of the spin of
the other particle in the x direction. And you can show using quantum
mechanics that if you measure the spin of an electron in the x direction, the
spin in the y or the z direction will be up with probability 50% and down with
probability 50%. I left this as an empirical fact because I don't know how to
explain it with actually resorting to doing quantum mechanics.

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Ntrails
Classical physics ALSO says that the other two directions have a 50%
probability of being red/green regardless of the value in the x "door".

With the quantum as stated above you still won't get 50% on random "doors",
because there is a chance that you open the same "door" on both particles
increasing the probability of getting a match beyond 50%?

To avoid having 55% on random doors, you'd need < 50% on the non equal
"doors", which implies something other than even chances.

(Quantum is beyond me I suspect!)

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Cookingboy
In Brian Greene's book "Fabrics of the Universe" he also mentioned some other
experiments that completely shattered our understanding of reality. One such
was the quantum eraser and especially delayed choice quantum eraser, which
COULD mean causality can be violated.

[http://en.wikipedia.org/wiki/Quantum_eraser_experiment](http://en.wikipedia.org/wiki/Quantum_eraser_experiment)

[http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser](http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser)

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jarradhope
Just tried finding this book you recommended.

I think it's "The Fabric of the Cosmos" [http://www.amazon.com/Fabric-Cosmos-
Texture-Reality-Penguin-...](http://www.amazon.com/Fabric-Cosmos-Texture-
Reality-Penguin-ebook/dp/B000XUDGV2/)

~~~
Cookingboy
You are right, I messed up the name :)

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lifeformed
Why do the 3-color passport stamps have to be distributed normally? If some
patterns were more common than others, than couldn't it explain the 55.55%?

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evo
That wouldn't matter (at least as I understand the article explanation).
There's 2^3 = 8 different stamp configurations, two of which (RRR/GGG)
trivially have 100% match likelyhood. The other six are all equivalent, and
they all predict the same thing. There's (3 choices of doors) * (3 choices of
doors) = 9 ways to expose the stamp configuration, and in any of the six
equivalent stamps there's five ways to match colors to four ways to differ,
5/9 = 55.55%, the expected distribution. [1]

The problem is that quantum mechanics predicts (and experiments show) that the
distribution you actually get is 50%, which is lower than what you would
expect no matter what stamp configuration you get.

On the other hand, it's possible that the way you choose which door to open is
not distributed randomly. One of the ways to reconcile Bell's theorem is that
there's a passport stamp that mind-controls you into picking doors with a 50%
distribution. It's not a very popular theory, but it exists. [2]

[1] Assuming RGG without loss of generality

    
    
      1-R 1-R = Match
      1-R 2-G = Miss
      1-R 3-G = Miss
      2-G 1-R = Miss
      2-G 2-G = Match
      2-G 3-G = Match
      3-G 1-R = Miss
      3-G 2-G = Match
      3-G 3-G = Match
    

Five matches to four misses.

[2][http://en.wikipedia.org/wiki/Superdeterminism](http://en.wikipedia.org/wiki/Superdeterminism)

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sriku
There is a gem of a book recommended at the bottom of the article - "boojums
all the way through".

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cowpig
Is it possible that the 3-door box is not doing the same thing as the 1-door
box? By this I mean that the 1-door box is measuring some hidden variable that
the 3-door box is not measuring?

