
NIST Physicists Show Ion Pairs Perform Enhanced &#039;Spooky Action&#039; - sconxu
https://www.nist.gov/news-events/news/2017/03/nist-physicists-show-ion-pairs-perform-enhanced-spooky-action
======
platz
susskind described entanglement in a bit different way than I'd heard - "that
entanglement allows one to know everything there is to know about a system of
particles (the whole), while knowing nothing about it's parts."

In the classical version of an information experiment, if i randomize
placement of objects A and B into 2 boxes, and send one of those boxes to
someone else - upon opening my box I instantly know whether the other box
contains object A or B. The Quantum Mechanical version of the above experiment
is very similar, except there could be several different degreees of freedom
to measure on upon opening my box (what angle of spin measure on, etc..)

So to me, that doesn't suggest that something "traveled" to the other box,
just like in the Classical version.

Rather, somehow I only "knew" the system at the beginning without knowing "any
of it's parts" (due to entanglement & superposition).

Then, just observing a degree of freedom in one the parts finally reveals what
the corresponding degree of freedom in the other part was.

This (intuitively) makes more sense to me than saying "information traveled"
and "action at a distance"

~~~
danbruc
_So to me, that doesn 't suggest that something "traveled" to the other box,
just like in the Classical version. Rather, somehow I only "knew" the system
at the beginning without knowing "any of it's parts" (due to entanglement &
superposition). Then, just observing a degree of freedom in one the parts
finally reveals what the corresponding degree of freedom in the other part
was. This (intuitively) makes more sense to me than saying "information
traveled" and "action at a distance"_

But exactly this is not the case, exactly this is the difference between
classical physics and quantum physics. Classically you place one coin in each
of the two boxes, heads in one, tails in the other. Nothing strange happens
here, the outcome is determined when setting up the boxes. When you look in
one of the box, you will see either heads or tails as determined by the setup.
The other box will have the coin showing the opposing side, also determined by
the setup.

The quantum case is very different. You again place one coin in each of the
two boxes, again one heads and one tails, but this time the coins are
constantly flipping. It is no longer predetermined whether you will get heads
or tails and only when you look in one of the boxes does the coin in there
stops flipping and you see either heads or tails. But more importantly the
other coin stops flipping at the very same time so that you will see the
opposing side when you look into the second box.

The correlation is in both cases established when the boxes are setup, the
coins will always show opposing sides. The quantum cases of course also
requires both coins flipping synchronously. But in the classical case the
exact outcome is also established during the setup while in the quantum case
the exact outcome is only established when one looks in the first box.

~~~
platz
> the coins are constantly flipping ... the other coin stops flipping at the
> very same time

I'm not sure this corresponds to my understanding of the wave function before
observation.

Just because the probabilities for each state is less than 1, to me doesn't
mean that it's "constantly flipping". Only that upon measurement there's a
probability that one of those states gets defined/constrained.

This is what i think susskind meant by understanding the whole (probabilities
of the wave function of the whole system), without understanding the parts
"the particles" i.e. it's kind of not right to think of just the parts here.
It's only the system+parts that must be thought of together (which of course
is why one of the reasons no-one truly understands it).

~~~
danbruc
_I 'm not sure this corresponds to my understanding of the wave function
before observation._

This was only meant as a classical model how the outcome is not predetermined,
I did not want to imply that the wave function oscillates back and forth
between two states or something like that. I could also have said that you
place two coins in each box and one randomly explodes when you look in the
box. And of course the corresponding coin in the second box also explodes
simultaneously.

------
nonbel
Why does this not describe the "entanglement" phenomenon:

1) Alice, Bob, and Charlie are in a room.

2) Alice has only an apple and a pear, seen by Charlie.

3) Charlie leaves the room.

4) Alice gives one of the two fruits to Bob.

5) Bob leaves the room to meet up with Charlie and starts eating the pear.

6) Charlie instantly knows that Alice has the apple, no matter where she has
ended up in the universe (which is not spooky at all).

~~~
danbruc
Because Bob leaves the room with either an apple or a pear and this choice is
made inside the room. In quantum physics Bob would leave the room with half an
apple and half a pear, Charlie would ask Bob to eat the pear, and in this
moment Bob's half of the apple would teleport to Alice and Alice's half of the
pear to Bob. Charlie could also have asked Bob to eat the apple.

Very roughly speaking, this picture is actually flawed. Charlie can not choose
the fruit to eat in quantum mechanics. In this picture you would also transmit
Charlie's choice to Alice faster than the speed of light which is not possible
in quantum mechanics. The important part of this picture is that Bob does not
leave the room with a predetermined fruit, the choice happens later outside of
the room but Alice still always ends up with the other fruit, Alice and Bob
never end up with the same fruit.

~~~
nonbel
Thanks,

> "Charlie would ask Bob to eat the pear"

This seems to be the key part. So when they run experiments on this, a certain
result can be forced?

> "The important part is that Bob does not leave the room with predetermined
> fruit."

Right, is this aspect measured somehow or only inferred from the theory?

~~~
danbruc
I tried to set this straight in my comment. Charlie does not get to choose the
fruit, the fruit is chosen at random. I just allowed Charlie to make the
choice to emphasize that the choice happens outside of the room. Had I just
said the choice happens at random, then it would not be obvious why this
random choice could not also be made in the room with Alice. But then we were
back at Bob leaving the room with either an apple or a pear.

Have I look at my other comment with coins in boxes [1], that picture captures
the situation better and in a way that is not easily translated to fruits.

[1]
[https://news.ycombinator.com/item?id=13981054](https://news.ycombinator.com/item?id=13981054)

~~~
beojan
> I just allowed Charlie to make the choice to emphasize that the choice
> happens outside of the room.

The problem is that allowing Charlie to make the choice allows him to use
entanglement to transmit information faster than the speed of light.

------
Balgair
Oh cool! This experiment is very fun, not just from the results side. I was
able to get a tour with the photonic side of this set-up (not the atomic side,
as this paper elucidates). The photons are made entangled, then split and sent
into some fiber-optic cables that run about in the tracts in the hallways. The
rooms used to measure the entanglements are sufficiently far apart, but due to
budgets, are at right angles from the source. We only went to one of the
rooms, but the measurement devices are housed in marijuana grow pods you can
buy, as they tend to keep the temperature stable, have access for the wires
and cryogenic tubes, will keep out/in EM noise, and are pretty cheap. There
was a line on the floor of that room, off in the corner, that had where the
'light speed' signal from the other measurement room stopped when the
measurement (in the room we were in) was made, proving that the measurements
could not interact. If you ever get a chance, get a tour at NIST, it is well
worth whatever strings you have to pull. Getting to see _The_ United States
Second (where the US measures all of out time from) was a real highlight of my
scientific career.

------
mabbo
> “We are confident that the ions are 67 percent spooky,” said Ting Rei Tan,
> lead author

I love modern physics for lines like this.

~~~
komali2
I wonder if they were an even spookier 66.6...% spooky, but Ting Rei Tan
didn't want to say that cause that'd just be 2spoopy4me

------
headcanon
One think I've been wondering about spooky action is if entanglement reactions
are bound to the speed of light. As in, if one particle of the entangled pair
is manipulated, is there a "signal" that is "transmitted" at some speed? Or is
it "instant" in the sense that it transcends lightspeed? Or does this question
even make sense in this context? Quantum stuff gets weird fast since we have
very little basis in which to intuit it.

~~~
danbruc
It is instantly but you can not use it to transmit information.

Say you have a pair of entangled spins in a superposition of the two anti-
parallel states first spin up and second spin down or first spin down and
second spin up with equal probability for both states, i.e. each spin is up or
down with a probability of 50 % but the two spins always have opposing
orientations.

If you measure one of the spins, then there is no time, no matter how far the
spins are separated, in which you could measure the second spin to have the
same orientation as the one you just measured because the result of the
measurement somehow had not yet enough time to reached the second spin,
supposedly because this state change is limited to travel at the speed of
light.

It is as if the spins had secretly picked on of the two possible outcomes when
they were created but you just do not know which one until you perform a
measurement. But this is not the case, this is what is called a local hidden
variable theory and is ruled out by Bell test experiments. The spins have no
definite orientation until you measure the first one but after the first
measurement both spins instantaneously have a definit orientation no matter
how far separated.

~~~
tedsanders
There is no proof or strong evidence that this occurs instantly. Some
interpretations of quantum mechanics still satisfy locality.

[https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_m...](https://en.m.wikipedia.org/wiki/Interpretations_of_quantum_mechanics)

~~~
danbruc
One has to be careful what one means here. I meant it in the following
specific sense and we have good experimental evidence for this.

 _[...] there is no time, no matter how far the spins are separated, in which
you could measure the second spin to have the same orientation as the one you
just measured [...]_

If an interpretation makes use of non-locality to explain this fact is a
different matter, but experimentally it looks exactly like measurements
instantaneously affecting entangled partners.

------
chakalakasp
One of the more head exploding experiments I've seen regarding entanglement is
this one:

[https://youtu.be/u9bXolOFAB8](https://youtu.be/u9bXolOFAB8)

By all apparences, it seems to violate causality. It's one of those things
that make you suddenly stop and bemusedly wonder if maybe we've finally found
a kludge in the Universe's code.

 _edit_ BTW, if you'd like to know more about this experiment and why it has
ridiculous implications, check this PBS clip:
[https://youtu.be/8ORLN_KwAgs](https://youtu.be/8ORLN_KwAgs)

