DrmDoc Posted August 16, 2016 Share Posted August 16, 2016 Prepare for a new age of secure communication. According to this New York Times article on MSN, China has launched the first--that we know of--quantum satellite, which uses entangled photons to transmit information. The article says that the current transmission rate is glacial and compared the current status of this technology to that of the telegraph. The article contains links to other announcements about the launch and the nature of the technology. Enjoy! Link to comment Share on other sites More sharing options...
swansont Posted August 16, 2016 Share Posted August 16, 2016 It also explains entanglement in the predictable wrong way. Link to comment Share on other sites More sharing options...
StringJunky Posted August 16, 2016 Share Posted August 16, 2016 It also explains entanglement in the predictable wrong way. I thought so. What is the actual principle here they are using? Link to comment Share on other sites More sharing options...
DrmDoc Posted August 16, 2016 Author Share Posted August 16, 2016 It also explains entanglement in the predictable wrong way. Indeed? Please, elucidate. Link to comment Share on other sites More sharing options...
swansont Posted August 16, 2016 Share Posted August 16, 2016 I thought so. What is the actual principle here they are using? I could be wrong, since the article is basically science-free, but the obvious application is encryption. You can tell if someone intercepts the message. There's a quote to that effect in the story. Indeed? Please, elucidate. "Such teleportation involves entangling two photons so that a change in one would instantly affect the other in a predictable way." In entanglement the state of the particles is unknown. It is measurement that results in the predictable behavior, not a change. Once you make the measurement, the entanglement is broken. 1 Link to comment Share on other sites More sharing options...
StringJunky Posted August 16, 2016 Share Posted August 16, 2016 I could be wrong, since the article is basically science-free, but the obvious application is encryption. You can tell if someone intercepts the message. There's a quote to that effect in the story. "Such teleportation involves entangling two photons so that a change in one would instantly affect the other in a predictable way." In entanglement the state of the particles is unknown. It is measurement that results in the predictable behavior, not a change. Once you make the measurement, the entanglement is broken. And no information is exchanged. Link to comment Share on other sites More sharing options...
swansont Posted August 16, 2016 Share Posted August 16, 2016 And no information is exchanged. You can, if you separately exchange a key. Link to comment Share on other sites More sharing options...
StringJunky Posted August 16, 2016 Share Posted August 16, 2016 You can, if you separately exchange a key. But not within the entangled particles? Link to comment Share on other sites More sharing options...
swansont Posted August 16, 2016 Share Posted August 16, 2016 But not within the entangled particles? No, AFAIK. Link to comment Share on other sites More sharing options...
DrmDoc Posted August 17, 2016 Author Share Posted August 17, 2016 I could be wrong, since the article is basically science-free, but the obvious application is encryption. You can tell if someone intercepts the message. There's a quote to that effect in the story. "Such teleportation involves entangling two photons so that a change in one would instantly affect the other in a predictable way." In entanglement the state of the particles is unknown. It is measurement that results in the predictable behavior, not a change. Once you make the measurement, the entanglement is broken. How is quantum entanglement assessed if not measured? I'm somewhat familiar with the idea of entanglement relative to speculative notions such as teleportation. What are the facts or is it all sci-fi fantasy? Link to comment Share on other sites More sharing options...
swansont Posted August 17, 2016 Share Posted August 17, 2016 How is quantum entanglement assessed if not measured? That's not the point. The article says if you change one particle, you notice it in the other, and that's wrong. You can't notice anything until you measure the particle's state, and once you do, the entanglement is broken. Changing a particles's state at that point will do nothing. You aren't continuously monitoring the particle, like you can do classically. Link to comment Share on other sites More sharing options...
DrmDoc Posted August 17, 2016 Author Share Posted August 17, 2016 That's not the point. The article says if you change one particle, you notice it in the other, and that's wrong. You can't notice anything until you measure the particle's state, and once you do, the entanglement is broken. Changing a particles's state at that point will do nothing. You aren't continuously monitoring the particle, like you can do classically. So, this is one of those Schrodinger's cat type conundrums where observation influences state or is this something entirely different? I accessed this description of Quantum Entanglement which, if I understand correctly, essentially states that measuring one particle or particles of a pair or group correlates to the observed effects of the other entangled particle or particles--measuring one particle, changes the shared state of the other. Is that accurate? Link to comment Share on other sites More sharing options...
StringJunky Posted August 17, 2016 Share Posted August 17, 2016 (edited) So, this is one of those Schrodinger's cat type conundrums where observation influences state or is this something entirely different? I accessed this description of Quantum Entanglement which, if I understand correctly, essentially states that measuring one particle or particles of a pair or group correlates to the observed effects of the other entangled particle or particles--measuring one particle, changes the shared state of the other. Is that accurate? The entangled particles are in superposition (in both states) and when you have a look (collapse the wave function/break the the entanglement) the observed photon is in either one of the two states. If you know the state of the one you observe you know that the otther one is in the other state. You cannot predetermine what the outcome will be.or change anything. How the Chinese are using it I have no idea. Edited August 17, 2016 by StringJunky Link to comment Share on other sites More sharing options...
DrP Posted August 17, 2016 Share Posted August 17, 2016 oh man - now I'm confused again - from what you said SJ it sounds like the left shoe right shoe argument.... which I thought was proven wrong experimentally. If one is spin up when you test it does this mean the other is ALWAYS going to measure spin down? If so then how is this not just the pair of gloves argument? Link to comment Share on other sites More sharing options...
StringJunky Posted August 17, 2016 Share Posted August 17, 2016 (edited) oh man - now I'm confused again - from what you said SJ it sounds like the left shoe right shoe argument.... which I thought was proven wrong experimentally. If one is spin up when you test it does this mean the other is ALWAYS going to measure spin down? If so then how is this not just the pair of gloves argument? Yes, AFAIK,. always. Someone, probably swansont, once used a heads/tails of a coin analogy: if you flip a coin, you instantly know what the other side is. Edited August 17, 2016 by StringJunky Link to comment Share on other sites More sharing options...
DrP Posted August 17, 2016 Share Posted August 17, 2016 OK - Thanks - I am going to have to re-read over that spin experiment later - I thought I understood it.... :-/ There was a good you-tube vid that (I thought) cleared it for me. If what you say is true - then how do we know there is superstition and entanglement? Why not just if one is up then the other is down - why the entangled connection? (I guess the answer is in the experiment). I think Einstein suggested that they might not be connected once separated and that they were just like a pair of gloves where one is in one box and one in another. You open one box and find a left one then you know the right one is in the other. I thought this seemed logical too but the experiment showed otherwise.... I'll look it up when I am not at work. Thanks. Link to comment Share on other sites More sharing options...
StringJunky Posted August 17, 2016 Share Posted August 17, 2016 (edited) OK - Thanks - I am going to have to re-read over that spin experiment later - I thought I understood it.... :-/ There was a good you-tube vid that (I thought) cleared it for me. If what you say is true - then how do we know there is superstition and entanglement? Why not just if one is up then the other is down - why the entangled connection? (I guess the answer is in the experiment). I think Einstein suggested that they might not be connected once separated and that they were just like a pair of gloves where one is in one box and one in another. You open one box and find a left one then you know the right one is in the other. I thought this seemed logical too but the experiment showed otherwise.... I'll look it up when I am not at work. Thanks. I don't know properly how it works but the gloves are not in superposition; they don't have the potential to swap places/show a different state to the one they were put in initially. That's as much as I know. Edited August 17, 2016 by StringJunky 1 Link to comment Share on other sites More sharing options...
DrmDoc Posted August 17, 2016 Author Share Posted August 17, 2016 The entangled particles are in superposition (in both states) and when you have a look (collapse the wave function/break the the entanglement) the observed photon is in either one of the two states. If you know the state of the one you observe you know that the otther one is in the other state. You cannot predetermine what the outcome will be.or change anything. How the Chinese are using it I have no idea. I see. How does one determine superposition? How does know that the separate particles within a duo state share those qualities until observed or measured? Link to comment Share on other sites More sharing options...
StringJunky Posted August 17, 2016 Share Posted August 17, 2016 (edited) I see. How does one determine superposition? How does know that the separate particles within a duo state share those qualities until observed or measured? That, Sir, is beyond my ken. Edit: Re-reading your question: the photons were entangled together, by some process, in the first place and they can't share the same state. Edited August 17, 2016 by StringJunky Link to comment Share on other sites More sharing options...
DrP Posted August 17, 2016 Share Posted August 17, 2016 DrmDoc - I'm sure there was a good you tube vid that clearly describes the experiment that proves it - I'll try to find it when I get the time as I need to re-watch it as I have gotten myself confused again - good job I do not need to know anything about it for my line of work. lol. Link to comment Share on other sites More sharing options...
DrmDoc Posted August 17, 2016 Author Share Posted August 17, 2016 That, Sir, is beyond my ken. Logically, I think, superposition has to be more than supposition to be a valid observation. If observation is a form of measurement and the only determining factor, superposition is most likely supposition; wherein, particles are merely thought to exist in a duo state without direct evidence of same. This would seem to be very much like Schrodinger's cat, in my opinion. DrmDoc - I'm sure there was a good you tube vid that clearly describes the experiment that proves it - I'll try to find it when I get the time as I need to re-watch it as I have gotten myself confused again - good job I do not need to know anything about it for my line of work. lol. Thank you, I'd be very interested in viewing it. Link to comment Share on other sites More sharing options...
StringJunky Posted August 17, 2016 Share Posted August 17, 2016 (edited) Logically, I think, superposition has to be more than supposition to be a valid observation. If observation is a form of measurement and the only determining factor, superposition is most likely supposition; wherein, particles are merely thought to exist in a duo state without direct evidence of same. This would seem to be very much like Schrodinger's cat, in my opinion. ....As a result, the team were able to demonstrate conclusively that the universe does not obey local realism: the outcomes of measurements cannot be known in advance, and half of an entangled state can exert spooky action on its remote partner. Read more at: http://phys.org/news/2015-10-physicists-quantum-spookiness-schrodinger-cat.html#jCp Edited August 17, 2016 by StringJunky 1 Link to comment Share on other sites More sharing options...
DrmDoc Posted August 17, 2016 Author Share Posted August 17, 2016 That was a very interesting read. In quantum mechanics, if I now understand correctly, superposition describes a particle's continuous oscillation from one state to another, which only becomes fixed by observation. To support this principle, your link mention the double-slit experiment with which I'm very familiar. Still, it's difficult to understand how observation fix a particle's state unless it's merely our observation that is fixed--meaning we are only able to detect what we observe. I agree with Einstein, this is all very "Spooky." Link to comment Share on other sites More sharing options...
StringJunky Posted August 17, 2016 Share Posted August 17, 2016 (edited) That was a very interesting read. In quantum mechanics, if I now understand correctly, superposition describes a particle's continuous oscillation from one state to another, which only becomes fixed by observation. To support this principle, your link mention the double-slit experiment with which I'm very familiar. Still, it's difficult to understand how observation fix a particle's state unless it's merely our observation that is fixed--meaning we are only able to detect what we observe. I agree with Einstein, this is all very "Spooky." It's to do with wave functions (a mathematical concept) and when you make an observation you collapse it such that the respective states are revealed in the test subjects. Edited August 17, 2016 by StringJunky Link to comment Share on other sites More sharing options...
swansont Posted August 17, 2016 Share Posted August 17, 2016 So, this is one of those Schrodinger's cat type conundrums where observation influences state or is this something entirely different? I accessed this description of Quantum Entanglement which, if I understand correctly, essentially states that measuring one particle or particles of a pair or group correlates to the observed effects of the other entangled particle or particles--measuring one particle, changes the shared state of the other. Is that accurate? It doesn't change the state, since the state in undetermined. Measuring one means you know the state of both. I don't know properly how it works but the gloves are not in superposition; they don't have the potential to swap places/show a different state to the one they were put in initially. That's as much as I know. That's right. Where the glove or coin analogy fails is that in QM the particles are in an unknown state until they are measured. Thise analogies are used to show how measuring one particle tellls you about the other. Link to comment Share on other sites More sharing options...
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