6 ms·

Quantum ‘spookiness’ passes toughest test yet

53 points by jcr 11y ago

saurik 11y ago
FQXi (39 comments): https://news.ycombinator.com/item?id=10130203 https://news.ycombinator.com/item?id=10130203 Nature (1 comment) (same link as this one): https://news.ycombinator.com/item?id=10135260 https://news.ycombinator.com/item?id=10135260 Scientific American (0 comments): https://news.ycombinator.com/item?id=10139598 https://news.ycombinator.com/item?id=10139598 Ars Technica (0 comments): https://news.ycombinator.com/item?id=10141658 https://news.ycombinator.com/item?id=10141658 Forbes (0 comments): https://news.ycombinator.com/item?id=10129946 https://news.ycombinator.com/item?id=10129946
- jcr 11y ago
  Thanks saurik, I somehow missed the fqxi.org article submission when searching before (re)submitting the nature.com article.
geeklodhi 11y ago
I found this article more helpful http://googler700.blogspot.com.tr/2015/08/self-seo-training.html http://googler700.blogspot.com.tr/2015/08/self-seo-training....
fryguy 11y ago
My understanding is that entanglement doesn't actually allow for transfer any information faster than the speed of light but is more like having two coins sealed in a box and given to two parties, that "God" always keeps the same way up until they're opened. You can manipulate them by flipping the coins over, but you don't know what it was originally. You can open your box and see that your coin is heads, and send a conventional message to the other person that says "if your coin is heads, then attack at dawn", but you don't know what the coin is until you open it, so are still reliant on sending the message over means that obey the speed of light in order to transfer the information. Is that an accurate (given that it's an analogy) description of how entanglement works, or does this work disprove that idea and is what was mentioned as Einstein's idea?
- lclemente 11y ago
  I think the problem with your analogy is that it doesn't include the measurement basis. Consider polarization of a photon: you can either distinguish between horizontal or vertical polarization with a measurement, so your basis looks like a "+". Or you can distinguish between diagonal polarizaitons, so your basis looks like an "X". Now, considering two photons, you don't know which basis Alice or Bob will choose in advance. If you just say "the photon is polarized horizontally", then their outcomes will be random if they measure in the "X" basis. If you include so-called "hidden variables" for all possible measurements, then you're basically at Einstein's idea. (I've simplified some things above, so please don't quote me on it ;)
- dools 11y ago
  What you've quoted there is a good analogy of an entangled state. In reality there are several differences, and the biggest piece of misinformation is that measurement of one system somehow "collapses a wave function" in the other system which isn't the case. The phenomenon of entanglement is that measurements of certain things are either perfectly correlated or anti-correlated. Eg. Measurement of spin along some axis on electron A will always be -1 when measurement of spin along the same axis of electron B is +1. The similarity to 2 coins is: if i have a 1972 coin and a 1973 coin, and give one to you randomly, then you go a million light years away and look at your coin and find you have the 1973 coin, you will know I have the 1972 coin. Although this is only a simplified analogy of entanglement the important point is that the state was prepared before we separated, and no information has been communicated. When you try to understand this in terms of classical physics, it's weird. But it's not classical physics. I wrote more about it here: https://news.ycombinator.com/item?id=10133674 https://news.ycombinator.com/item?id=10133674 Also check out the leonard susskind messenger lectures for a quick overview and his stanford continuing ed lectures on youtube for the long version :)
  - coldtea 11y ago
    >The similarity to 2 coins is: if i have a 1972 coin and a 1973 coin, and give one to you randomly, then you go a million light years away and look at your coin and find you have the 1973 coin, you will know I have the 1972 coin. Although this is only a simplified analogy of entanglement the important point is that the state was prepared before we separated, and no information has been communicated. When you try to understand this in terms of classical physics, it's weird. If that was the case (the coin analogy) it would be perfectly understandable by classical physics. In fact it wouldn't even need physics to understand it, just common sense. If that was the case there wouldn't be any EPR paradox etc. The coin analogy is very misleading in this way -- and doesn't convey the problems physicists have had with explaining this phenomenon.
crishoj 11y ago
Can anyone explain (in layman-like terms) how one goes about transporting a single photon over a distance of 1.3km? I really like to have a general idea of the technology involved. "The researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 kilometres apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location."
- gus_massa 11y ago
  They use a optic fiber. This version has mare technical details, but is still understandable: http://arstechnica.com/science/2015/08/experiment-confirms-that-quantum-mechanics-scoffs-at-our-local-reality/ http://arstechnica.com/science/2015/08/experiment-confirms-t... (HN: https://news.ycombinator.com/item?id=10141658 https://news.ycombinator.com/item?id=10141658 (4 points, 12 hours ago, 1 comment)) > To get around this, the researchers started with the diamonds over a kilometer apart in two different labs at the Delft University of Technology. They entangled each electron spin with a photon, then sent the photons over fiber optic cable to a third lab somewhere in between. There, the photons were entangled, which in turn caused the electrons in the diamonds to be entangled as well.
  - crishoj 11y ago
    Another enlightening point is that there is a significant loss in the optic fibers: > The whole process was horribly inefficient, with a success rate of 6.4 × 10−9, mostly because photons kept getting lost in the fiber optic cables. But, over the course of nine days, the setup managed to successfully entangle the nitrogen vacancies 245 times.
skarap 11y ago
Every time I read something on quantum theory I can't help but notice how close to notion of magic it feels like. And I've studied physics in college. Some time ago I thought how strange these all would look to someone who had no knowledge in physics at all. But then I got it: two particles in different galaxies being entangled is not much different from calling someone on the other side of the globe using a cellphone if you don't have prior knowledge/beliefes about either.
- stefantalpalaru 11y ago
  I see it as a failure of the model. When the explanation is irrational, does a scientist stop to wonder at the irrationality of the universe instead of trying to come up with better explanations?
  - adekok 11y ago
    Thousands of people have been trying for 50 years. Every model they've tried has turned out to be wrong. It's easy to say "come up with better explanations". It's not very helpful, though.
    - stefantalpalaru 11y ago
      It's easy to dismiss criticism by complaining that it doesn't propose solutions, but the two are distinct and unrelated activities. The purpose of criticism is not to be directly helpful by proposing better solutions, but to help eliminate the wrong ones.
  - skarap 11y ago
    While I agree that science is currently seeing only small part of the picture, I don't believe scientists have stopped trying to find explanations. And what is more important - it's very hard to judge if the explanation is rational. Every science is built on some axioms which define what is rational and what is not. That's why I guess the progress happens step by step (each next step expanding what one would consider rational).
rhelsing 11y ago
Sometimes I feel like the writers from Lost are in control of our universe, improvising plot twists as we get seemingly closer to understanding how things work.

53 points by jcr 11y ago

FQXi (39 comments): https://news.ycombinator.com/item?id=10130203 https://news.ycombinator.com/item?id=10130203 Nature (1 comment) (same link as this one): https://news.ycombinator.com/item?id=10135260 https://news.ycombinator.com/item?id=10135260 Scientific American (0 comments): https://news.ycombinator.com/item?id=10139598 https://news.ycombinator.com/item?id=10139598 Ars Technica (0 comments): https://news.ycombinator.com/item?id=10141658 https://news.ycombinator.com/item?id=10141658 Forbes (0 comments): https://news.ycombinator.com/item?id=10129946 https://news.ycombinator.com/item?id=10129946

jcr 11y ago
Thanks saurik, I somehow missed the fqxi.org article submission when searching before (re)submitting the nature.com article.

geeklodhi 11y ago

I found this article more helpful http://googler700.blogspot.com.tr/2015/08/self-seo-training.html http://googler700.blogspot.com.tr/2015/08/self-seo-training....

fryguy 11y ago

My understanding is that entanglement doesn't actually allow for transfer any information faster than the speed of light but is more like having two coins sealed in a box and given to two parties, that "God" always keeps the same way up until they're opened. You can manipulate them by flipping the coins over, but you don't know what it was originally. You can open your box and see that your coin is heads, and send a conventional message to the other person that says "if your coin is heads, then attack at dawn", but you don't know what the coin is until you open it, so are still reliant on sending the message over means that obey the speed of light in order to transfer the information. Is that an accurate (given that it's an analogy) description of how entanglement works, or does this work disprove that idea and is what was mentioned as Einstein's idea?

lclemente 11y ago
I think the problem with your analogy is that it doesn't include the measurement basis. Consider polarization of a photon: you can either distinguish between horizontal or vertical polarization with a measurement, so your basis looks like a "+". Or you can distinguish between diagonal polarizaitons, so your basis looks like an "X". Now, considering two photons, you don't know which basis Alice or Bob will choose in advance. If you just say "the photon is polarized horizontally", then their outcomes will be random if they measure in the "X" basis. If you include so-called "hidden variables" for all possible measurements, then you're basically at Einstein's idea. (I've simplified some things above, so please don't quote me on it ;)
dools 11y ago
What you've quoted there is a good analogy of an entangled state. In reality there are several differences, and the biggest piece of misinformation is that measurement of one system somehow "collapses a wave function" in the other system which isn't the case. The phenomenon of entanglement is that measurements of certain things are either perfectly correlated or anti-correlated. Eg. Measurement of spin along some axis on electron A will always be -1 when measurement of spin along the same axis of electron B is +1. The similarity to 2 coins is: if i have a 1972 coin and a 1973 coin, and give one to you randomly, then you go a million light years away and look at your coin and find you have the 1973 coin, you will know I have the 1972 coin. Although this is only a simplified analogy of entanglement the important point is that the state was prepared before we separated, and no information has been communicated. When you try to understand this in terms of classical physics, it's weird. But it's not classical physics. I wrote more about it here: https://news.ycombinator.com/item?id=10133674 https://news.ycombinator.com/item?id=10133674 Also check out the leonard susskind messenger lectures for a quick overview and his stanford continuing ed lectures on youtube for the long version :)
- coldtea 11y ago
  >The similarity to 2 coins is: if i have a 1972 coin and a 1973 coin, and give one to you randomly, then you go a million light years away and look at your coin and find you have the 1973 coin, you will know I have the 1972 coin. Although this is only a simplified analogy of entanglement the important point is that the state was prepared before we separated, and no information has been communicated. When you try to understand this in terms of classical physics, it's weird. If that was the case (the coin analogy) it would be perfectly understandable by classical physics. In fact it wouldn't even need physics to understand it, just common sense. If that was the case there wouldn't be any EPR paradox etc. The coin analogy is very misleading in this way -- and doesn't convey the problems physicists have had with explaining this phenomenon.

crishoj 11y ago

Can anyone explain (in layman-like terms) how one goes about transporting a single photon over a distance of 1.3km? I really like to have a general idea of the technology involved. "The researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 kilometres apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location."

gus_massa 11y ago
They use a optic fiber. This version has mare technical details, but is still understandable: http://arstechnica.com/science/2015/08/experiment-confirms-that-quantum-mechanics-scoffs-at-our-local-reality/ http://arstechnica.com/science/2015/08/experiment-confirms-t... (HN: https://news.ycombinator.com/item?id=10141658 https://news.ycombinator.com/item?id=10141658 (4 points, 12 hours ago, 1 comment)) > To get around this, the researchers started with the diamonds over a kilometer apart in two different labs at the Delft University of Technology. They entangled each electron spin with a photon, then sent the photons over fiber optic cable to a third lab somewhere in between. There, the photons were entangled, which in turn caused the electrons in the diamonds to be entangled as well.
- crishoj 11y ago
  Another enlightening point is that there is a significant loss in the optic fibers: > The whole process was horribly inefficient, with a success rate of 6.4 × 10−9, mostly because photons kept getting lost in the fiber optic cables. But, over the course of nine days, the setup managed to successfully entangle the nitrogen vacancies 245 times.

skarap 11y ago

Every time I read something on quantum theory I can't help but notice how close to notion of magic it feels like. And I've studied physics in college. Some time ago I thought how strange these all would look to someone who had no knowledge in physics at all. But then I got it: two particles in different galaxies being entangled is not much different from calling someone on the other side of the globe using a cellphone if you don't have prior knowledge/beliefes about either.

stefantalpalaru 11y ago
I see it as a failure of the model. When the explanation is irrational, does a scientist stop to wonder at the irrationality of the universe instead of trying to come up with better explanations?
- adekok 11y ago
  Thousands of people have been trying for 50 years. Every model they've tried has turned out to be wrong. It's easy to say "come up with better explanations". It's not very helpful, though.
  - stefantalpalaru 11y ago
    It's easy to dismiss criticism by complaining that it doesn't propose solutions, but the two are distinct and unrelated activities. The purpose of criticism is not to be directly helpful by proposing better solutions, but to help eliminate the wrong ones.
- skarap 11y ago
  While I agree that science is currently seeing only small part of the picture, I don't believe scientists have stopped trying to find explanations. And what is more important - it's very hard to judge if the explanation is rational. Every science is built on some axioms which define what is rational and what is not. That's why I guess the progress happens step by step (each next step expanding what one would consider rational).

rhelsing 11y ago

Sometimes I feel like the writers from Lost are in control of our universe, improvising plot twists as we get seemingly closer to understanding how things work.