Spooky action achieved at record distance

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Spooky action achieved at record distance

Post by Witness » Mon Jun 19, 2017 3:30 am

Science wrote:Summary

Quantum entanglement has moved out of this world and into space. In a study that shows China's growing mastery of both the quantum world and space science, a team of physicists reports that it sent eerily intertwined quantum particles from a satellite to ground stations separated by 1200 kilometers. Quantum physics says the quantum states of entangled objects remain linked until one of them is measured. That measurement instantly determines the quantum state of the other, no matter how far away—the "spooky action" at a distance that Albert Einstein was suspicious of. Results from China's Micius satellite show that the effect is real at a record distance, and the achievement foreshadows other quantum experiments in space.
http://science.sciencemag.org/content/3 ... login-pane (but full text behind paywall)

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Re: Spooky action achieved at record distance

Post by Anaxagoras » Mon Jun 19, 2017 4:11 am

That's interesting. I've heard of "spooky action at a distance" but I don't know enough to say much about it. However, I do wonder whether "action at a distance" is totally necessary to explain the phenomenon, of if that's just one possible hypothesis.
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Re: Spooky action achieved at record distance

Post by xouper » Mon Jun 19, 2017 5:03 am

Anaxagoras wrote:That's interesting. I've heard of "spooky action at a distance" but I don't know enough to say much about it. However, I do wonder whether "action at a distance" is totally necessary to explain the phenomenon, of if that's just one possible hypothesis.
Notice that they don't say that the act of "measurement" allows the observer to choose which state the remote particle will be in.

In other words, they don't seem to be willing to say it can be used to send information between the two linked particles. Which leads me to suppose there is no information being sent and thus no action, spooky or otherwise.

As you suggest, there might be another explanation not requiring spooky action at a distance.

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Re: Spooky action achieved at record distance

Post by ed » Mon Jun 19, 2017 10:21 am

If you modulate the pattern of measurement couldn't you have that modulation then occur at a distance ie. TV or interwebs or the like? Instantaneously?

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Re: Spooky action achieved at record distance

Post by xouper » Mon Jun 19, 2017 11:02 am

ed wrote:If you modulate the pattern of measurement couldn't you have that modulation then occur at a distance ie. TV or interwebs or the like? Instantaneously?
Excellent question. (Translation: why didn't I think of that.)

What does it mean to "modulate the pattern of measurement"?

I'm not trying to evade the question. I simply do not know what you have in mind. I might guess at what you meant, but asking is easier and less risky.

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Re: Spooky action achieved at record distance

Post by ed » Mon Jun 19, 2017 11:14 am

Well, if you have N things that you can measure and they are ordered n1 ... nn then you might treat them as though they are a bmp and measure them in such a way as to get an image.

"Modulate" might be the wrong word, I assume we are in a world of binary, right? On/Off. I was thinking FMish stuff originally.

I wonder if there is a theoretical temporal component ... like the change occuring BEFORE the action. That would allow for a way to break the bank at Monte Carlo, or win a war.

eta: I've trademarked the word "Interociter" so don't get any cute ideas.
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Re: Spooky action achieved at record distance

Post by ed » Mon Jun 19, 2017 11:16 am

You could 3-d print instantly anywhere. You could, given a simple receiver, create a very complicated object.

Actually, the Interociter is sorta a good intellectual model.
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Re: Spooky action achieved at record distance

Post by ed » Mon Jun 19, 2017 11:17 am

Given the tech to break down a biological organism, one could transport a critter.
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Re: Spooky action achieved at record distance

Post by Anaxagoras » Mon Jun 19, 2017 12:42 pm

I don't think it works like that, ed. Sorry.

Personally I think if there is some kind of information transfer from one particle to another, it happens when they become "entangled", not when they are measured.
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Re: Spooky action achieved at record distance

Post by ed » Mon Jun 19, 2017 1:19 pm

Quantum physics says the quantum states of entangled objects remain linked until one of them is measured. That measurement instantly determines the quantum state of the other, no matter how far away—the "spooky action" at a distance that Albert Einstein was suspicious of. Results from China's Micius satellite show that the effect is real at a record distance, and the achievement foreshadows other quantum experiments in space.
Am I reading this wrong?
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Re: Spooky action achieved at record distance

Post by xouper » Mon Jun 19, 2017 1:20 pm

ed wrote:Well, if you have N things that you can measure and they are ordered n1 ... nn then you might treat them as though they are a bmp and measure them in such a way as to get an image.
I'm not sure I follow what you have in mind. How does measuring "thing N" allow you to choose which state it is (0 or 1)?

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Re: Spooky action achieved at record distance

Post by Rob Lister » Mon Jun 19, 2017 1:24 pm

xouper wrote:
ed wrote:Well, if you have N things that you can measure and they are ordered n1 ... nn then you might treat them as though they are a bmp and measure them in such a way as to get an image.
I'm not sure I follow what you have in mind. How does measuring "thing N" allow you to choose which state it is (0 or 1)?
And since you cannot know the state of N1 until you measure it, how do you know whether N2 was measured 0 or 1 unless you go back to N1 and ask? So yes, the change happens instantaneous, but their is no useful information garnered.
Last edited by Rob Lister on Mon Jun 19, 2017 1:25 pm, edited 1 time in total.

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Re: Spooky action achieved at record distance

Post by ceptimus » Mon Jun 19, 2017 1:25 pm

You can't use the 'spooky action at a distance' to transmit information faster than the speed of light. That's one part of the spookiness.

So you have observers, call them A and B, making measurements on a stream of entangled particles. Now both A and B will get results that independently pass all tests for randomness - but if they keep a record of their results and later get together to compare them (or communicate the results by some regular communication channel) then they will find that they both got "the same" results.

As an analogy, if I were able to send you 100 coins that had been entangled with 100 coins I keep here, then we could both flip them at any time (including simultaneously) and record 100 instances of heads or tails. We'd both get a random string of heads and tails - just as with regular coins - but when we meet up to compare notes we'd find that whenever you flipped 'heads' then I will have flipped the corresponding 'tails'.

It's spookier than that with the particles as one observer may constrain the measurements made - say she's measuring the polarization of a particle - she could measure it up/down or left/right or maybe at some intermediate angle. As soon as the measurement is made, it "forces" the entangled pair particle to have the same polarization - so there really is action at a distance that can be verified when later comparing notes - but as the result of each measurement is an apparently random yes/no result then no useful information can be transmitted in real time.

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Re: Spooky action achieved at record distance

Post by Abdul Alhazred » Mon Jun 19, 2017 1:35 pm

ed wrote:Actually, the Interociter is sorta a good intellectual model.
Especially the built in death ray. :coolspecs:
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Re: Spooky action achieved at record distance

Post by ceptimus » Mon Jun 19, 2017 1:38 pm

Oops. cross-posted with Rob.

But let me expand on the polarization example - it's not just that the pair of particles are polarized randomly and the measurement says 'yes' or 'no' - measuring one of the particles forces the entangled particle to have the same polarization.

Say observers A and B can each set their polarizing filter angle at one of six orientations, using the numbers one to six on a clock face. Before each observation each observer rolls a six-sided-die and they use the randomly generated numbers from the dice to each set their filter angle.

Now when they get together and compare results, unless they happen to have set their two filters at right angles (say by rolling a 1 and a 4 respectively) then the results will match. Say one observer set his filter at position 1 and the other observer at position 2 - then the results will be the same. Or if the one observer rolled a 2 and the other a 6 then the results will be opposite.

This could not happen if the polarization of the particles were random and the two measurements just found whether it was nearer or further away than ninety degrees from the filter angle - it seems that whatever the angle "was before measuring" (which is not really meaningful in the quantum world) then the act of measuring the polarization with the filter set at '2' forces the polarization to either be exactly in line with '2' or exactly at right angles to it - and the entangled particle, even if it is billions of miles away, simultaneously adopts the same polarization.

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Re: Spooky action achieved at record distance

Post by ed » Mon Jun 19, 2017 1:49 pm

xouper wrote:
ed wrote:Well, if you have N things that you can measure and they are ordered n1 ... nn then you might treat them as though they are a bmp and measure them in such a way as to get an image.
I'm not sure I follow what you have in mind. How does measuring "thing N" allow you to choose which state it is (0 or 1)?
No. You measure it so that it's paired thingie changes.
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Re: Spooky action achieved at record distance

Post by xouper » Mon Jun 19, 2017 3:45 pm

ed wrote:
xouper wrote:
ed wrote:Well, if you have N things that you can measure and they are ordered n1 ... nn then you might treat them as though they are a bmp and measure them in such a way as to get an image.
I'm not sure I follow what you have in mind. How does measuring "thing N" allow you to choose which state it is (0 or 1)?
No. You measure it so that it's paired thingie changes.
Changes from what? You do not know the state of either particle until one of them is measured, and then you know the state of both of them. What "change" are you referring to?

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Re: Spooky action achieved at record distance

Post by xouper » Mon Jun 19, 2017 3:47 pm

ceptimus wrote:As an analogy, if I were able to send you 100 coins that had been entangled with 100 coins I keep here, then we could both flip them at any time (including simultaneously) and record 100 instances of heads or tails. We'd both get a random string of heads and tails - just as with regular coins - but when we meet up to compare notes we'd find that whenever you flipped 'heads' then I will have flipped the corresponding 'tails'.
Pardon my failure to fully understand your explanation, but I'm not sure that is a completely valid analogy. Are you suggesting that an entangled coin is not flipped until it is "measured"? How do you know the entangled pair of coins were not both flipped (simultaneously as a pair) at the moment they were created as an entangled pair but you simply do not know which one is heads until you look at one of them at a later time? What am I missing in your analogy?

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Re: Spooky action achieved at record distance

Post by Rob Lister » Mon Jun 19, 2017 3:48 pm

I recommend we leave this thread behind us. It will cause detention and anonymity.


The reference to spooky is clearly racist.

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Re: Spooky action achieved at record distance

Post by ceptimus » Mon Jun 19, 2017 4:53 pm

xouper wrote:
ceptimus wrote:As an analogy, if I were able to send you 100 coins that had been entangled with 100 coins I keep here, then we could both flip them at any time (including simultaneously) and record 100 instances of heads or tails. We'd both get a random string of heads and tails - just as with regular coins - but when we meet up to compare notes we'd find that whenever you flipped 'heads' then I will have flipped the corresponding 'tails'.
Pardon my failure to fully understand your explanation, but I'm not sure that is a completely valid analogy. Are you suggesting that an entangled coin is not flipped until it is "measured"? How do you know the entangled pair of coins were not both flipped (simultaneously as a pair) at the moment they were created as an entangled pair but you simply do not know which one is heads until you look at one of them at a later time? What am I missing in your analogy?
You're taking the analogy too far. I was just saying that if it were possible to entangle two coins so that in one sense they behaved like entangled particles, then when one of them is flipped and the result recorded, the outcome of flipping the other coin is then predestined.

So when the first coin is flipped the outcome is just the usual random 50:50 distribution of heads/tails. The person that flipped it now knows in advance which way the other coin will land when it is flipped. He could phone the other person up and say, 'when you flip it I know it will land heads!' but of course that information is just travelling at regular telephone line speed. If you were trying to communicate faster than light, then it's no use - the second person just sees the usual random result of flipping a coin. It only becomes spooky if and when the first coin flipper is able to communicate with the second (by conventional light-speed-or-slower means) and is then able to predict the coin toss if it's not yet been flipped - or if it has been flipped the result is already known without being told.

It's the fact that the two flippers both know that they have the same coin toss result without speaking about it that makes the technique useful for cryptography - the secret message can be sent in a way that requires knowledge of the coin toss results to decode. The message still has to be sent by regular means but the key is sent by the spooky entangled means. It's impossible for an eavesdropper to 'see' the entangled part of the information as when he makes any attempt to measure it the quantum entanglement is broken and the two people who are trying to send the message would know and then not transmit the actual (encoded) secret message. The procedure would be: 1. send the entangled particles and measure them. 2. communicate by normal unencrypted means and make sure they both agree that various 'checksums' for the entangled stream match. Then they can be sure that they both hold the same "random" stream of results and the sender can use the random stream as a one-time key to encrypt the secret message and send it via normal open communication. A one-use random key is universally acknowledged to be a 100% secure way of encrypting and transmitting a message, and the entangled particles allow a one-time key to be shared by two people in a way that they can be sure (assuming quantum physics theory is correct) is immune to eavesdropping.