5 ms·

Which is still extremely useful for things like probes. Instant comm's to Mars rover or even voyager. Of course no ones figured out how to make use of entangl

Which is still extremely useful for things like probes. Instant comm's to Mars rover or even voyager. Of course no ones figured out how to make use of entanglement for information transfer. Pops up a lot in Sci-Fi, reading Three-Bodied Problem now and the aliens sent "sophons" basically probes the size of protons at near the speed of light to earth from Alpha Centauri, they arrived in a few years while their invasion fleet will take 400 years to get here. The sophons spy and interfere with earth communicating with aliens via quantum entanglement.

teraflop 8y ago
> Of course no ones figured out how to make use of entanglement for information transfer. Saying "no one's figured it out" is misleading because it creates the impression that it's an engineering problem to be solved. According to our best understanding of quantum mechanics, the laws of physics fundamentally do not permit faster-than-light communication, whether through entanglement or any other mechanism.
- Filligree 8y ago
  Well, of course they don't. How would you even begin to build a simulator for something like that? Communications overhead between the nodes is bad enough as it is.
- SigmundA 8y ago
  I was trying to imply that its probably the best avenue for research, and also we may never figure it out, might be a dead end. However I would say the reason it is used so much in sci-fi is it currently the one way we can cause action at a distance faster than light, which is so tantalizingly close to communication.
  - codethief 8y ago
    I wouldn't say we're close to FTL transfer of information in any meaningful way. In particular, > we can cause action at a distance is not true, either.
    - SigmundA 8y ago
      >is not true, either. I didn't think this was settled and depends on your interpretation of QM: https://en.wikipedia.org/wiki/Action_at_a_distance https://en.wikipedia.org/wiki/Action_at_a_distance
      - codethief 8y ago
        …and on your precise definition of "action and a distance", yes. But there is something like standard textbook quantum mechanics which most physicists subscribe to, i.e. the Copenhagen interpretation, and while I'm not saying this is the interpretation everyone should follow and believe in (in fact, there are good reasons to be dissatisfied with this interpretation), the term "action at a distance" was coined in the context of the Copenhagen interpretation, so I think should therefore also be interpreted in this context. Now, Copenhagen is a local and non-realist theory, the latter of which meaning among other things that the wave function is not believed to be an object of reality. Therefore, in this interpretation, the collapse of the wave function is merely a tool for predicting the outcome of a measurement and not something that's believed to actually happen. The same thing goes for an "instantaneous collapse" at a distance — this action does not exist in reality. I know there is probably going to be someone who objects to me saying that Copenhagen is non-realist and local. But those people will have to explain to me how they would bring the actual existence of the wave function and its collapse into agreement with relativity and, in particular, with different observers who come to different conclusions about when the wave function collapses. For instance, for one observer, it might be Alice who causes the wave function to collapse and, thus, Bob to measure a certain outcome but then there is always going to be another observer who will say the exact opposite, namely that Bob caused the collapse. So, essentially, if you really think the wave function is an object of reality, all hell breaks lose. Needless to say, even if you completely disregard these issues and still want to think of Copenhagen as a realist but then necessarily non-local theory (in which case I'd say you should really give your theory a different name), this is all just splitting hairs because the only thing that matters is that there's no FTL transfer of information. This is the only experimentally verifiable statement we can make.
  - akvadrako 8y ago
    There is no reason to think quantum entanglement could be used for FTL communication. The theory which gives us entanglement also proves (mathematically) it can't be used for communication.
- ganzuul 8y ago
  Our understanding of the model is thought to be quite poor. Further, we should not ever mistake the model for reality or attempt to fit data to predictions. The cosmos might not be anthropomorphic.
  - Strilanc 8y ago
    The no communication theorem is not the no communication hypothesis, it's actually a math proof. You start from the principles of quantum mechanics (unitarity, etc), define what you mean by entanglement (non-factoring states), and prove it's not possible to use those states to win the communication game. This is an aspect of quantum mechanics that we understand extremely well.

teraflop 8y ago

> Of course no ones figured out how to make use of entanglement for information transfer. Saying "no one's figured it out" is misleading because it creates the impression that it's an engineering problem to be solved. According to our best understanding of quantum mechanics, the laws of physics fundamentally do not permit faster-than-light communication, whether through entanglement or any other mechanism.

Filligree 8y ago
Well, of course they don't. How would you even begin to build a simulator for something like that? Communications overhead between the nodes is bad enough as it is.
SigmundA 8y ago
I was trying to imply that its probably the best avenue for research, and also we may never figure it out, might be a dead end. However I would say the reason it is used so much in sci-fi is it currently the one way we can cause action at a distance faster than light, which is so tantalizingly close to communication.
- codethief 8y ago
  I wouldn't say we're close to FTL transfer of information in any meaningful way. In particular, > we can cause action at a distance is not true, either.
  - SigmundA 8y ago
    >is not true, either. I didn't think this was settled and depends on your interpretation of QM: https://en.wikipedia.org/wiki/Action_at_a_distance https://en.wikipedia.org/wiki/Action_at_a_distance
    - codethief 8y ago
      …and on your precise definition of "action and a distance", yes. But there is something like standard textbook quantum mechanics which most physicists subscribe to, i.e. the Copenhagen interpretation, and while I'm not saying this is the interpretation everyone should follow and believe in (in fact, there are good reasons to be dissatisfied with this interpretation), the term "action at a distance" was coined in the context of the Copenhagen interpretation, so I think should therefore also be interpreted in this context. Now, Copenhagen is a local and non-realist theory, the latter of which meaning among other things that the wave function is not believed to be an object of reality. Therefore, in this interpretation, the collapse of the wave function is merely a tool for predicting the outcome of a measurement and not something that's believed to actually happen. The same thing goes for an "instantaneous collapse" at a distance — this action does not exist in reality. I know there is probably going to be someone who objects to me saying that Copenhagen is non-realist and local. But those people will have to explain to me how they would bring the actual existence of the wave function and its collapse into agreement with relativity and, in particular, with different observers who come to different conclusions about when the wave function collapses. For instance, for one observer, it might be Alice who causes the wave function to collapse and, thus, Bob to measure a certain outcome but then there is always going to be another observer who will say the exact opposite, namely that Bob caused the collapse. So, essentially, if you really think the wave function is an object of reality, all hell breaks lose. Needless to say, even if you completely disregard these issues and still want to think of Copenhagen as a realist but then necessarily non-local theory (in which case I'd say you should really give your theory a different name), this is all just splitting hairs because the only thing that matters is that there's no FTL transfer of information. This is the only experimentally verifiable statement we can make.
- akvadrako 8y ago
  There is no reason to think quantum entanglement could be used for FTL communication. The theory which gives us entanglement also proves (mathematically) it can't be used for communication.
ganzuul 8y ago
Our understanding of the model is thought to be quite poor. Further, we should not ever mistake the model for reality or attempt to fit data to predictions. The cosmos might not be anthropomorphic.
- Strilanc 8y ago
  The no communication theorem is not the no communication hypothesis, it's actually a math proof. You start from the principles of quantum mechanics (unitarity, etc), define what you mean by entanglement (non-factoring states), and prove it's not possible to use those states to win the communication game. This is an aspect of quantum mechanics that we understand extremely well.