21 ms·

Undetectable quantum computation and communication for alien civilizations

156 points by mathgenius 5y ago

suifbwish 5y ago
Quantum communication requires a continually renewed source of mutually shared entangled pairs to send communication. When entangled states collapse, which they must do in order to send information, the particle pairs are no longer entangled and can thus no longer send information. These civilizations would have to find a way to keep a stable quantum pairing which can be observed without collapsing the quantum state, which is the equivalent of finding a way to stop black holes from emitting Hawking radiation; essentially they would need to find a way to stop entropy as we know it in order to make long distance quantum communication sustainable.
- mrfusion 5y ago
  Place a beam splitter between you and fire a laser. Get entangled particles back. Or place an entangled particle emitter between you
- trutannus 5y ago
  > These advanced civilizations would require technology I can't think of how to implement I mean, that's part of what makes them advanced civilizations.
  - suifbwish 5y ago
    Advancements in technology will probably not do away with what we already understand about physics, it will likely just add more details.
    - trutannus 5y ago
      >Advancements in technology will probably not do away with what we already understand about physics, it will likely just add more details Could have been said in the 1800's about why we'd never have quantum computers.
- Moodles 5y ago
  Is it really "equivalent"? I get both problems are about entropy in the universe but I would have thought managing the state of a black is harder, due to its suction into oblivion and whatnot. I don't know much about if it's possible to make entangled particles stable somehow, or whether you could maybe just have a lot of them so you never run out even if a lot become untangled naturally. Doesn't quantum key exchange use entangled particles? So it must be possible to keep them stable for at least a little while.
- throw1234651234 5y ago
  I don't get it - wasn't it concluded that instantaneous communication is impossible, aka you can't transmit information EVEN if you were to take a decade to move two entangled particles apart, all you would get is data from 10 years ago?
  - grepfru_it 5y ago
    FTL communication is not possible. You have access to the entangled particle right now but, to send information, you are bound to the limits of the classical channel (the 10 year problem transmitting information about the entanglement)
    - fasdf23qwe 5y ago
      This would be correct if causality is an absolut certainty in all the universe, the whole time, but what if causality it actually isn't a certainty in some contexts? Tadah..you would get ala "FTL" comms enabled.
      - drdeca 5y ago
        Isn’t this just saying that if you could send a signal faster than c, then you could send a signal faster than c? I don’t see your point.
        fasdf23qwe 5y ago
        Sorry, I didn't wanted to write it like that was psychosis somehow. I meant, causality as I understand, it could be not a fully understood concept. We could still find evidence - in the future - that there are phenomena capable of "evade" the cause-effect principle. https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly https://en.wikipedia.org/wiki/Faster-than-light_neutrino_ano...
        fasdf23qwe 5y ago
        To add more speculation, the idea from the movie "Tenet" could be a way to effectively surpase C in long distance communications: reversed entropy matter. You could just send a ship or some kind of vesel with reversed entropy to a star and it will arrive years later, but years sooner that it was launched. Matter is more or less energy, what if this trick could be done with reversed entropy energy: radio, x-rays, gamma rays, etc.
duncan-donuts 5y ago
Looking forward to the ELI5 version of this. It sounds interesting but I have no idea what they're saying.
- kinghtown 5y ago
  that’s because it’s undetectable. no one knows what they are saying.
  - pugworthy 5y ago
    I believe the parent meant he doesn't know what the paper is saying, not what the aliens might be saying.
    - kinghtown 5y ago
      noted
    - duncan-donuts 5y ago
      Yeah, exactly. This is way over my head.
      - kinghtown 5y ago
        it’s over my head too. apparently the signal is in outer space.
- yourenotsmart 5y ago
  It seems like a wild and possibly inaccurate speculation on the use of quantum effects for communication. Before we start speculating how aliens communicate, we need to have some idea how WE can communicate via the same means, even in a most crude way (like sending one bit of information few feet away). Otherwise saying "well aliens maybe know more so maybe they can do it" could be used to submit a paper about just anything at all we fancy. Say time machines. So far, measuring the properties of entangled particles has not been demonstrated as capable of transferring information faster than light. You can only do the math and conclude what happened when you have BOTH RESULTS. And to have both results, you need to communicate them via traditional means, like giving the other team a phone call, or, you know, walking there and asking them.
godelski 5y ago
The author uses the first person plural, I suggest he adds his cat as a co-author[0] [0] https://en.wikipedia.org/wiki/F._D._C._Willard https://en.wikipedia.org/wiki/F._D._C._Willard
- soheil 5y ago
  > Entanglement, in our experience, only manifests itself when the cleverest of our species capture and protect it appropriately in controlled and delicate experiments. He definitely comes off as slightly off-putting.
- kook_throwaway 5y ago
  I love that the "See Also" section links to this "list of animals with fraudulent diplomas" https://en.m.wikipedia.org/wiki/List_of_animals_awarded_human_credentials https://en.m.wikipedia.org/wiki/List_of_animals_awarded_huma...
gus_massa 5y ago
> The distributed computation requires classical communication between receivers, however, similar to standard measurement-based computation, that communication is of purely random outcomes and so can be indistinguishable from noise. The main problem of this idea is that you also need a classical channel to transmit the information. You can use natural sources of entangled photons as proposed[1], but you will need a classic channel that can be detected. In the classic channel you will see a random stream of data, so it will be impossible to decode, but you can still see that there is some communication. [1] I think it's not so easy, but let's ignore this second objection.
- yourenotsmart 5y ago
  Our own encrypted communication is indistinguishable from noise, save for the initial handshake, which represents a detectable pattern, but mostly because we happen to already have the full specification of the protocol handy. Additionally, entanglement can't be used for FTL communication, classical channel or not. So this, combined with the fact you don't need any quantum level mechanics for hidden communication that looks like noise... I'm unsure what the author is proposing and where that idea came to them.
  - thereddaikon 5y ago
    That's definitely untrue. You can fire up an SDR and easily pickup encrypted radios from businesses and public safety. You can even classify the protocol they are using, P25, DMR etc based on the characteristics of the signals. They are definitely not indistinguishable from noise. Low Probability of Intercept radios can be harder to pick up because they use various techniques like frequency hopping but even then they don't blend in to the background.
    - yourenotsmart 5y ago
      Knowing the popular protocols is an advantage you wouldn't have with "alien communication". Encryption in general doesn't try to hide itself, it just tries to hide the payload, so things like packet/frame structure, headers, handshake and so on can be relatively easy to pick up, because they're not hidden in the first place. Consider how unsophisticated the Enigma machine looks to modern eyes. Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Unlikely. Those are just few decades of difference on the same species with the same tech history.
mrkramer 5y ago
This reminds me of Quantum Cryptography in which Conjugate Coding [1] is used. Conjugate Coding is " A method of transmitting multiple messages in such a way that reading one destroys the others. This is called quantum multiplexing and it uses photons polarized in conjugate bases as "qubits" to pass information." Even if you can detect such communication it is hard to eavesdrop it because: "Quantum cryptographic systems take advantage of Heisenberg's uncertainty principle, according to which measuring a quantum system in general disturbs it and yields incomplete information about its state before the measurement. Eavesdropping on a quantum communication channel therefore causes an unavoidable disturbance, alerting the legitimate users." [2] [1] https://en.wikipedia.org/wiki/Conjugate_coding https://en.wikipedia.org/wiki/Conjugate_coding [2] https://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC.html https://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC.html
- max_ 5y ago
  Interesting. Is there a way you could implement this phenomenon in software/hardware and use it as a next secure channel for communication?
  - go_elmo 5y ago
    Since it is no inherently present physical fact in classical systems, it will have to fight with classical problems (bugs / backdoors etc) which would throw you back to classical encryption for security
  - deleted 5y ago
    [deleted]
- randomname93857 5y ago
  OTOH, an extraterrestrial civilization can use this method to detect other civilizations - they'll be able to detect when someone attempts to eavesdrop on them. cool.
5cott0 5y ago
Do not answer! Do not answer! Do not answer!
BigProofOfStake 5y ago
Sounds like someone just wrapped up their reading of The Three Body Problem series.
- ctoth 5y ago
  Terry Rudolph's[0] 132 research works with 7384 citations and 7159 reads, including: Creation of Entangled Photonic States Using Linear Optics[1]. Or yeah, maybe he just finished Remembrance of Earth's Past [0]: https://en.wikipedia.org/wiki/Terry_Rudolph https://en.wikipedia.org/wiki/Terry_Rudolph [1]: https://www.researchgate.net/scientific-contributions/Terry-Rudolph-10499139 https://www.researchgate.net/scientific-contributions/Terry-...
  - KingFelix 5y ago
    Just raised $450M so now release all sorts of wacky stuff that is usually pub talk to arxiv! Terry is also the grandson of Schrodinger!
par 5y ago
i dont know what any of this means, but it was some of the coolest sounding sentences i've read in a while.
fdfasd2312fasd 5y ago
* Perhaps they are everywhere? Perhaps.
playguardin 5y ago
This is one of the ones where I read one paragraph. Have no idea what's going on, so go the comments directly.
grishka 5y ago
Would a sufficiently advanced civilization really settle for communication that crawls at the speed of light though? And before you say "anything faster than light is impossible": it's impossible according to our current understanding of physics. How much that understanding aligns with reality, especially with relation to quantum mechanics, is debatable.
- krapp 5y ago
  Until there's actual evidence to the contrary, the "debate" is one side with all of the science and the other side waving around a Star Trek technical manual.
  - grishka 5y ago
    History knows multiple examples when people had a theory about something and it agreed with their observations, but then they observed a discrepancy, and then another one, and tried to rectify them by adding more and more rather arbitrary conditions or exceptions to their theory. Until it was proven completely wrong and a much better, and much simpler, explanation was found. One example is this "phlogiston theory"[1] describing how and why things burn before we knew about atoms and molecules. It did its job and explained people's observations about the process of combustion. But then it was found out that for some substances, their weight increases after they've been burnt. This was explained by phlogiston having negative weight... sometimes. Or being lighter than air, also sometimes. Another one is how we first thought that the universe revolves around the earth. And then we had complex formulas that described the motion of celestial bodies as we see them on the sky. And guess what? It turned out to be much simpler than we thought. And then our current theories can't explain redshift, so we assume that the universe must be expanding. And they can't explain how outer parts of galaxies spin faster than they should be spinning, so we invent dark matter to reconcile that. See a pattern? [1] https://en.wikipedia.org/wiki/Phlogiston_theory https://en.wikipedia.org/wiki/Phlogiston_theory
    - krapp 5y ago
      The pattern I see is one of constant refinement as technology and prior knowledge allows for more effective experimentation, greater observations, and physical models which increase in accuracy over time, despite still being incomplete. General and special relativity are the most thoroughly tested and confirmed models ever to have existed to date [0,1]. And while it is currently not possible to reconcile quantum mechanics and general relativity, quantum mechanics was reconciled with special relativity by Dirac in 1928, and the light speed limit on the transmission of information remains. And there are no observations which suggest a flaw in current models akin to redshift or the orbit of Mercury which suggest the light speed limit is incorrect, rather, experiment has always validated it[2]. We now know that even the speed of gravity itself is limited to the speed of light[3]. It seems as if you're confident that any day now we'll discover that relativity was just as wrong as alchemy and phlogiston all along, and that there's some simple and elegant truth everyone missed that somehow both describes the universe more accurately than current models and also just happens to allow for arbitrary FTL communication and travel. We'll have to agree to disagree. [0]https://en.wikipedia.org/wiki/Tests_of_general_relativity https://en.wikipedia.org/wiki/Tests_of_general_relativity [1]https://en.wikipedia.org/wiki/Tests_of_special_relativity https://en.wikipedia.org/wiki/Tests_of_special_relativity [2]https://en.wikipedia.org/wiki/Speed_of_light https://en.wikipedia.org/wiki/Speed_of_light [3]https://en.wikipedia.org/wiki/Speed_of_gravity https://en.wikipedia.org/wiki/Speed_of_gravity
fasdf23qwe 5y ago
Just reading the comments.. if there are aliens reading over our shoulders, we'd be looking like neanderthals speculating about electricity or nuclear reactors... if the technology described in the paper actually exists, it would be far away from our current understanding of the reality.
- state_less 5y ago
  > if there are aliens reading over our shoulders, we'd be looking like neanderthals Presumably, even these supposed aliens would have been relatively evolutionarily young once too.
jboy55 5y ago
I've always thought that given the sheer numbers involved its a given there are advanced civilizations and that the lack of detectable light communications means the following. Alien civilizations have found such a vastly superior method of communications that they have given up on electromagnetism as a method. The thought experiment is this, if we discovered a vastly superior method of communication, we would probably switch over and abandon light. And if we turned this new 'dish' towards space and found thousands of civilizations communicating... why would we ever try to communicate with EM in space ever again? This means that the time each civilization spends trying to communicate with EM is the time between discovering EM comms and the 'new' mechanism. The number of current alien civilizations communicating in EM are just those currently in that band, and the ratio of alien civilizations doing EM is the (average duration of this band) to the (average age of a civilization). It would be like a civilization currently on earth, only at the level of smoke signals, trying to determine if there are other civilizations by looking for smoke on the horizon.
- fasdf23qwe 5y ago
  We (as in human race), metaphorically could be - right now - in the middle of a city like NY, looking for someone sending signals with smoke, and being surrounded by multiple modern communication systems, everywhere around us. Maybe we have always been surrounded by aliens communications and we didn't notice it, like what happened with electricity, it was all around humanity, all the time humans existed, and it was discovery just recently.
- analog31 5y ago
  Something that's occurred to me is that radio is a bit more than a century old, and at the present time, we are still using EM radiation, but a huge portion of our data bandwidth is being transported along enclosed waveguides, i.e., fiber optics, and transmission lines that have no long range dipole, such as coaxial and twisted pair cable. The net bandwidth of our open-air comms has increased by orders of magnitude, but all the while being designed to operate at ever lower power levels using modulation strategies that increasingly resemble noise, using antennas that avoid radiating into space for the sake of power savings. It could be that our civilization had a 1-2 century time window for being detectable from afar, before we effectively go dark. A superior method of communication might be a robot that, while it can't travel as fast, can engage in much more elaborate communication when it reaches its destination, e.g., carrying out trade, negotiations, cultural exchange, whatever. Also, the energy delivered by a robot, if it can steer itself to its destination, is not subject to the inverse square law of intensity. We have sent robots to visit the planets, because there's a limit to what we can learn by interrogating them with telescopes and antennas from Earth. Speaking of smoke signals, we may be inadvertently communicating our presence by the rapid change of the chemical composition of our atmosphere. Aliens equipped with a sufficiently sensitive spectrometer could scan the heavens for unusual chemical activity on known planets.
ackbar03 5y ago
Of course, its how the "Buggers" communicate between themselves! I'm surprised nobodies brought up the Ansible from Orson Scott Card's books yet. Its the first thing that comes to mind everytime I hear about quantum entanglement. The first time I came across the concept in Ender's Game I thought it was purely science fiction but a pretty neat idea. The fact that something similar can actually be achieved has always been mind-blowing for me, it's like I'm gradually living out science fiction. A bit off topic but Ender's Game was such a good book, especially reading it in high-school, it just introduced so many new concepts
- giantrobot 5y ago
  The Ansible in Card's books is purely science fiction. The Ansible's allowed faster-than-light two-way communication. Quantum entanglement does not.
  - czbond 5y ago
    It is late - but while watching an episode of spacetime+ the host stated an entangled pair could be millions of miles apart and one could immediately cause a change in the other. This would be faster than light
    - ackbar03 5y ago
      As an arm-chair quantum physicist, I found this article helpful https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-reasons-quantum-entanglement-doesnt-allow-faster-than-light-communication/?sh=1826d6ee3a1e https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-r... If the entangled pair is measured precisely at the same time, both parties get the same value instantly. However this fact itself does not allow for actual communication/information passing. For that there needs to be a way to actually control the state. Or something like that Lol
      - dfasdf1231 5y ago
        Lets say I'm in NY, now I go to ask to join a cooking course, they say me: "we will let you know if you're accepted or not". Then I take a plane to the other side of the planet, Japan. We have some pending information, a link between the cooking course acceptation and me. The link will keep existing even if I take a trip to Mars. Then I got accepted in the cooking course, the information about the acceptance changes instantaneously in the whole universe, including in my head (currently in Japan, thousands of miles away from the place when the cooking course decision to accept me occurs). Is this quantum entanglement somehow? It seems to check all the boxes, including that the information changes instantaneously in both sides (I got accepted! even if now I'm in Japan), but I wouldn't know about it till they send me the news using a standard non-quantum channel. FTL comms aren't possible at all here, etc. Then I ask, entanglement occurs continously at levels in universe, when two entities somehow get to share a question, a pending information? Of course I think I'm missing something (a degree or PhD in physics for starters), that's why I'm asking. Thanks in advance.
altitudinous 5y ago
An analogy... I live in Australia, here there are endless straight highways through the outback. Beside the highway there are thousands of huge termite mounds with thousands upon thousands of termites in each one. Termites live a pretty organised and civilised life in their mound, they even probably wander onto the highway a fair bit, but have no idea what they have walked on to, or furthermore conceive the big picture of what the purpose of the highway is or even that a city or town is at the end. The analogy is of course that we are the termites, and the universe is the highway, outback, roads and cities. It would take quite an inconceivable leap for a termite to stumble onto the beginning of the meaning of the highway, let alone everything else.
nfc 5y ago
This just made me think how much the influence on civilizations that act based on some "Dark Forest" type of hypothesis could change based on what these civilizations (believe to) know about physics
jurschreuder 5y ago
Maybe most aliens (except us) have the intelligence to stay under the radar

156 points by mathgenius 5y ago

Quantum communication requires a continually renewed source of mutually shared entangled pairs to send communication. When entangled states collapse, which they must do in order to send information, the particle pairs are no longer entangled and can thus no longer send information. These civilizations would have to find a way to keep a stable quantum pairing which can be observed without collapsing the quantum state, which is the equivalent of finding a way to stop black holes from emitting Hawking radiation; essentially they would need to find a way to stop entropy as we know it in order to make long distance quantum communication sustainable.

mrfusion 5y ago
Place a beam splitter between you and fire a laser. Get entangled particles back. Or place an entangled particle emitter between you
trutannus 5y ago
> These advanced civilizations would require technology I can't think of how to implement I mean, that's part of what makes them advanced civilizations.
- suifbwish 5y ago
  Advancements in technology will probably not do away with what we already understand about physics, it will likely just add more details.
  - trutannus 5y ago
    >Advancements in technology will probably not do away with what we already understand about physics, it will likely just add more details Could have been said in the 1800's about why we'd never have quantum computers.
Moodles 5y ago
Is it really "equivalent"? I get both problems are about entropy in the universe but I would have thought managing the state of a black is harder, due to its suction into oblivion and whatnot. I don't know much about if it's possible to make entangled particles stable somehow, or whether you could maybe just have a lot of them so you never run out even if a lot become untangled naturally. Doesn't quantum key exchange use entangled particles? So it must be possible to keep them stable for at least a little while.
throw1234651234 5y ago
I don't get it - wasn't it concluded that instantaneous communication is impossible, aka you can't transmit information EVEN if you were to take a decade to move two entangled particles apart, all you would get is data from 10 years ago?
- grepfru_it 5y ago
  FTL communication is not possible. You have access to the entangled particle right now but, to send information, you are bound to the limits of the classical channel (the 10 year problem transmitting information about the entanglement)
  - fasdf23qwe 5y ago
    This would be correct if causality is an absolut certainty in all the universe, the whole time, but what if causality it actually isn't a certainty in some contexts? Tadah..you would get ala "FTL" comms enabled.
    - drdeca 5y ago
      Isn’t this just saying that if you could send a signal faster than c, then you could send a signal faster than c? I don’t see your point.
      - fasdf23qwe 5y ago
        Sorry, I didn't wanted to write it like that was psychosis somehow. I meant, causality as I understand, it could be not a fully understood concept. We could still find evidence - in the future - that there are phenomena capable of "evade" the cause-effect principle. https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly https://en.wikipedia.org/wiki/Faster-than-light_neutrino_ano...
      - fasdf23qwe 5y ago
        To add more speculation, the idea from the movie "Tenet" could be a way to effectively surpase C in long distance communications: reversed entropy matter. You could just send a ship or some kind of vesel with reversed entropy to a star and it will arrive years later, but years sooner that it was launched. Matter is more or less energy, what if this trick could be done with reversed entropy energy: radio, x-rays, gamma rays, etc.

duncan-donuts 5y ago

Looking forward to the ELI5 version of this. It sounds interesting but I have no idea what they're saying.

kinghtown 5y ago
that’s because it’s undetectable. no one knows what they are saying.
- pugworthy 5y ago
  I believe the parent meant he doesn't know what the paper is saying, not what the aliens might be saying.
  - kinghtown 5y ago
    noted
  - duncan-donuts 5y ago
    Yeah, exactly. This is way over my head.
    - kinghtown 5y ago
      it’s over my head too. apparently the signal is in outer space.
yourenotsmart 5y ago
It seems like a wild and possibly inaccurate speculation on the use of quantum effects for communication. Before we start speculating how aliens communicate, we need to have some idea how WE can communicate via the same means, even in a most crude way (like sending one bit of information few feet away). Otherwise saying "well aliens maybe know more so maybe they can do it" could be used to submit a paper about just anything at all we fancy. Say time machines. So far, measuring the properties of entangled particles has not been demonstrated as capable of transferring information faster than light. You can only do the math and conclude what happened when you have BOTH RESULTS. And to have both results, you need to communicate them via traditional means, like giving the other team a phone call, or, you know, walking there and asking them.

godelski 5y ago

The author uses the first person plural, I suggest he adds his cat as a co-author[0] [0] https://en.wikipedia.org/wiki/F._D._C._Willard https://en.wikipedia.org/wiki/F._D._C._Willard

soheil 5y ago
> Entanglement, in our experience, only manifests itself when the cleverest of our species capture and protect it appropriately in controlled and delicate experiments. He definitely comes off as slightly off-putting.
kook_throwaway 5y ago
I love that the "See Also" section links to this "list of animals with fraudulent diplomas" https://en.m.wikipedia.org/wiki/List_of_animals_awarded_human_credentials https://en.m.wikipedia.org/wiki/List_of_animals_awarded_huma...

gus_massa 5y ago

> The distributed computation requires classical communication between receivers, however, similar to standard measurement-based computation, that communication is of purely random outcomes and so can be indistinguishable from noise. The main problem of this idea is that you also need a classical channel to transmit the information. You can use natural sources of entangled photons as proposed[1], but you will need a classic channel that can be detected. In the classic channel you will see a random stream of data, so it will be impossible to decode, but you can still see that there is some communication. [1] I think it's not so easy, but let's ignore this second objection.

yourenotsmart 5y ago
Our own encrypted communication is indistinguishable from noise, save for the initial handshake, which represents a detectable pattern, but mostly because we happen to already have the full specification of the protocol handy. Additionally, entanglement can't be used for FTL communication, classical channel or not. So this, combined with the fact you don't need any quantum level mechanics for hidden communication that looks like noise... I'm unsure what the author is proposing and where that idea came to them.
- thereddaikon 5y ago
  That's definitely untrue. You can fire up an SDR and easily pickup encrypted radios from businesses and public safety. You can even classify the protocol they are using, P25, DMR etc based on the characteristics of the signals. They are definitely not indistinguishable from noise. Low Probability of Intercept radios can be harder to pick up because they use various techniques like frequency hopping but even then they don't blend in to the background.
  - yourenotsmart 5y ago
    Knowing the popular protocols is an advantage you wouldn't have with "alien communication". Encryption in general doesn't try to hide itself, it just tries to hide the payload, so things like packet/frame structure, headers, handshake and so on can be relatively easy to pick up, because they're not hidden in the first place. Consider how unsophisticated the Enigma machine looks to modern eyes. Now throw some modern encrypted traffic back at them, would they even understand there's signal in there? Unlikely. Those are just few decades of difference on the same species with the same tech history.

mrkramer 5y ago

This reminds me of Quantum Cryptography in which Conjugate Coding [1] is used. Conjugate Coding is " A method of transmitting multiple messages in such a way that reading one destroys the others. This is called quantum multiplexing and it uses photons polarized in conjugate bases as "qubits" to pass information." Even if you can detect such communication it is hard to eavesdrop it because: "Quantum cryptographic systems take advantage of Heisenberg's uncertainty principle, according to which measuring a quantum system in general disturbs it and yields incomplete information about its state before the measurement. Eavesdropping on a quantum communication channel therefore causes an unavoidable disturbance, alerting the legitimate users." [2] [1] https://en.wikipedia.org/wiki/Conjugate_coding https://en.wikipedia.org/wiki/Conjugate_coding [2] https://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC.html https://www.cs.mcgill.ca/~crepeau/CRYPTO/Biblio-QC.html

max_ 5y ago
Interesting. Is there a way you could implement this phenomenon in software/hardware and use it as a next secure channel for communication?
- go_elmo 5y ago
  Since it is no inherently present physical fact in classical systems, it will have to fight with classical problems (bugs / backdoors etc) which would throw you back to classical encryption for security
- deleted 5y ago
  [deleted]
randomname93857 5y ago
OTOH, an extraterrestrial civilization can use this method to detect other civilizations - they'll be able to detect when someone attempts to eavesdrop on them. cool.

5cott0 5y ago

Do not answer! Do not answer! Do not answer!

BigProofOfStake 5y ago

Sounds like someone just wrapped up their reading of The Three Body Problem series.

ctoth 5y ago
Terry Rudolph's[0] 132 research works with 7384 citations and 7159 reads, including: Creation of Entangled Photonic States Using Linear Optics[1]. Or yeah, maybe he just finished Remembrance of Earth's Past [0]: https://en.wikipedia.org/wiki/Terry_Rudolph https://en.wikipedia.org/wiki/Terry_Rudolph [1]: https://www.researchgate.net/scientific-contributions/Terry-Rudolph-10499139 https://www.researchgate.net/scientific-contributions/Terry-...
- KingFelix 5y ago
  Just raised $450M so now release all sorts of wacky stuff that is usually pub talk to arxiv! Terry is also the grandson of Schrodinger!

par 5y ago

i dont know what any of this means, but it was some of the coolest sounding sentences i've read in a while.

fdfasd2312fasd 5y ago

* Perhaps they are everywhere? Perhaps.

playguardin 5y ago

This is one of the ones where I read one paragraph. Have no idea what's going on, so go the comments directly.

grishka 5y ago

Would a sufficiently advanced civilization really settle for communication that crawls at the speed of light though? And before you say "anything faster than light is impossible": it's impossible according to our current understanding of physics. How much that understanding aligns with reality, especially with relation to quantum mechanics, is debatable.

krapp 5y ago
Until there's actual evidence to the contrary, the "debate" is one side with all of the science and the other side waving around a Star Trek technical manual.
- grishka 5y ago
  History knows multiple examples when people had a theory about something and it agreed with their observations, but then they observed a discrepancy, and then another one, and tried to rectify them by adding more and more rather arbitrary conditions or exceptions to their theory. Until it was proven completely wrong and a much better, and much simpler, explanation was found. One example is this "phlogiston theory"[1] describing how and why things burn before we knew about atoms and molecules. It did its job and explained people's observations about the process of combustion. But then it was found out that for some substances, their weight increases after they've been burnt. This was explained by phlogiston having negative weight... sometimes. Or being lighter than air, also sometimes. Another one is how we first thought that the universe revolves around the earth. And then we had complex formulas that described the motion of celestial bodies as we see them on the sky. And guess what? It turned out to be much simpler than we thought. And then our current theories can't explain redshift, so we assume that the universe must be expanding. And they can't explain how outer parts of galaxies spin faster than they should be spinning, so we invent dark matter to reconcile that. See a pattern? [1] https://en.wikipedia.org/wiki/Phlogiston_theory https://en.wikipedia.org/wiki/Phlogiston_theory
  - krapp 5y ago
    The pattern I see is one of constant refinement as technology and prior knowledge allows for more effective experimentation, greater observations, and physical models which increase in accuracy over time, despite still being incomplete. General and special relativity are the most thoroughly tested and confirmed models ever to have existed to date [0,1]. And while it is currently not possible to reconcile quantum mechanics and general relativity, quantum mechanics was reconciled with special relativity by Dirac in 1928, and the light speed limit on the transmission of information remains. And there are no observations which suggest a flaw in current models akin to redshift or the orbit of Mercury which suggest the light speed limit is incorrect, rather, experiment has always validated it[2]. We now know that even the speed of gravity itself is limited to the speed of light[3]. It seems as if you're confident that any day now we'll discover that relativity was just as wrong as alchemy and phlogiston all along, and that there's some simple and elegant truth everyone missed that somehow both describes the universe more accurately than current models and also just happens to allow for arbitrary FTL communication and travel. We'll have to agree to disagree. [0]https://en.wikipedia.org/wiki/Tests_of_general_relativity https://en.wikipedia.org/wiki/Tests_of_general_relativity [1]https://en.wikipedia.org/wiki/Tests_of_special_relativity https://en.wikipedia.org/wiki/Tests_of_special_relativity [2]https://en.wikipedia.org/wiki/Speed_of_light https://en.wikipedia.org/wiki/Speed_of_light [3]https://en.wikipedia.org/wiki/Speed_of_gravity https://en.wikipedia.org/wiki/Speed_of_gravity

fasdf23qwe 5y ago

Just reading the comments.. if there are aliens reading over our shoulders, we'd be looking like neanderthals speculating about electricity or nuclear reactors... if the technology described in the paper actually exists, it would be far away from our current understanding of the reality.

state_less 5y ago
> if there are aliens reading over our shoulders, we'd be looking like neanderthals Presumably, even these supposed aliens would have been relatively evolutionarily young once too.

jboy55 5y ago

I've always thought that given the sheer numbers involved its a given there are advanced civilizations and that the lack of detectable light communications means the following. Alien civilizations have found such a vastly superior method of communications that they have given up on electromagnetism as a method. The thought experiment is this, if we discovered a vastly superior method of communication, we would probably switch over and abandon light. And if we turned this new 'dish' towards space and found thousands of civilizations communicating... why would we ever try to communicate with EM in space ever again? This means that the time each civilization spends trying to communicate with EM is the time between discovering EM comms and the 'new' mechanism. The number of current alien civilizations communicating in EM are just those currently in that band, and the ratio of alien civilizations doing EM is the (average duration of this band) to the (average age of a civilization). It would be like a civilization currently on earth, only at the level of smoke signals, trying to determine if there are other civilizations by looking for smoke on the horizon.

fasdf23qwe 5y ago
We (as in human race), metaphorically could be - right now - in the middle of a city like NY, looking for someone sending signals with smoke, and being surrounded by multiple modern communication systems, everywhere around us. Maybe we have always been surrounded by aliens communications and we didn't notice it, like what happened with electricity, it was all around humanity, all the time humans existed, and it was discovery just recently.
analog31 5y ago
Something that's occurred to me is that radio is a bit more than a century old, and at the present time, we are still using EM radiation, but a huge portion of our data bandwidth is being transported along enclosed waveguides, i.e., fiber optics, and transmission lines that have no long range dipole, such as coaxial and twisted pair cable. The net bandwidth of our open-air comms has increased by orders of magnitude, but all the while being designed to operate at ever lower power levels using modulation strategies that increasingly resemble noise, using antennas that avoid radiating into space for the sake of power savings. It could be that our civilization had a 1-2 century time window for being detectable from afar, before we effectively go dark. A superior method of communication might be a robot that, while it can't travel as fast, can engage in much more elaborate communication when it reaches its destination, e.g., carrying out trade, negotiations, cultural exchange, whatever. Also, the energy delivered by a robot, if it can steer itself to its destination, is not subject to the inverse square law of intensity. We have sent robots to visit the planets, because there's a limit to what we can learn by interrogating them with telescopes and antennas from Earth. Speaking of smoke signals, we may be inadvertently communicating our presence by the rapid change of the chemical composition of our atmosphere. Aliens equipped with a sufficiently sensitive spectrometer could scan the heavens for unusual chemical activity on known planets.

ackbar03 5y ago

Of course, its how the "Buggers" communicate between themselves! I'm surprised nobodies brought up the Ansible from Orson Scott Card's books yet. Its the first thing that comes to mind everytime I hear about quantum entanglement. The first time I came across the concept in Ender's Game I thought it was purely science fiction but a pretty neat idea. The fact that something similar can actually be achieved has always been mind-blowing for me, it's like I'm gradually living out science fiction. A bit off topic but Ender's Game was such a good book, especially reading it in high-school, it just introduced so many new concepts

giantrobot 5y ago
The Ansible in Card's books is purely science fiction. The Ansible's allowed faster-than-light two-way communication. Quantum entanglement does not.
- czbond 5y ago
  It is late - but while watching an episode of spacetime+ the host stated an entangled pair could be millions of miles apart and one could immediately cause a change in the other. This would be faster than light
  - ackbar03 5y ago
    As an arm-chair quantum physicist, I found this article helpful https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-reasons-quantum-entanglement-doesnt-allow-faster-than-light-communication/?sh=1826d6ee3a1e https://www.forbes.com/sites/chadorzel/2016/05/04/the-real-r... If the entangled pair is measured precisely at the same time, both parties get the same value instantly. However this fact itself does not allow for actual communication/information passing. For that there needs to be a way to actually control the state. Or something like that Lol
    - dfasdf1231 5y ago
      Lets say I'm in NY, now I go to ask to join a cooking course, they say me: "we will let you know if you're accepted or not". Then I take a plane to the other side of the planet, Japan. We have some pending information, a link between the cooking course acceptation and me. The link will keep existing even if I take a trip to Mars. Then I got accepted in the cooking course, the information about the acceptance changes instantaneously in the whole universe, including in my head (currently in Japan, thousands of miles away from the place when the cooking course decision to accept me occurs). Is this quantum entanglement somehow? It seems to check all the boxes, including that the information changes instantaneously in both sides (I got accepted! even if now I'm in Japan), but I wouldn't know about it till they send me the news using a standard non-quantum channel. FTL comms aren't possible at all here, etc. Then I ask, entanglement occurs continously at levels in universe, when two entities somehow get to share a question, a pending information? Of course I think I'm missing something (a degree or PhD in physics for starters), that's why I'm asking. Thanks in advance.

altitudinous 5y ago

An analogy... I live in Australia, here there are endless straight highways through the outback. Beside the highway there are thousands of huge termite mounds with thousands upon thousands of termites in each one. Termites live a pretty organised and civilised life in their mound, they even probably wander onto the highway a fair bit, but have no idea what they have walked on to, or furthermore conceive the big picture of what the purpose of the highway is or even that a city or town is at the end. The analogy is of course that we are the termites, and the universe is the highway, outback, roads and cities. It would take quite an inconceivable leap for a termite to stumble onto the beginning of the meaning of the highway, let alone everything else.

nfc 5y ago

This just made me think how much the influence on civilizations that act based on some "Dark Forest" type of hypothesis could change based on what these civilizations (believe to) know about physics

jurschreuder 5y ago

Maybe most aliens (except us) have the intelligence to stay under the radar