Undetectable quantum computation and communication for alien civilizations
arxiv.org
arxiv.org
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.
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.
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.
There are a lot of problems with this idea and it comes up predictably in every SETI discussion ever.
For starters the inverse square law makes it extremely unlikely any two civilizations would ever detect each other's spurious emissions. Omnidirectional sources of EM radiation readily detectable at interstellar distances are called stars. If you tried to build an omnidirectional gigawatt TV transmitter it would melt itself rather than transmit anything. So the only way any civilization will have a signal detected by another is if they send an intentional and high gain (highly directional) signal towards other stars.
To that end the universe is filled with natural EM sources. Everything from the Big Bang to stars to giant clouds of gas emit some EM radiation. Even a planet like Earth with a strong magnetic field and a dense relatively moist atmosphere can see a large number of EM bands from the surface.
Even if some alien civilization uses sub-etha quantum blockchain to send e-mail it doesn't matter in terms of interstellar signals. Even on Earth a majority of our communication happens over cables (copper or fiber) or transmitters optimized for terrestrial reception. Our terrestrial communication systems might as well be sub-etha quantum blockchain since they're not useful at all for interstellar communication or detection.
Unless there's lots of natural sources of sub-etha quantum blockchain radiation there's not going to be many sub-etha quantum blockchain astronomers. There will be radio and visible (IR and UV included) EM astronomers because the universe is full of that radiation. If a civilization wants to send a detectable signal it's more likely to do so in the EM spectrum than some spectrum where alien astronomers are unlikely.
Of the EM spectrum it's also most likely intelligent civilizations would pick bands near natural sources. That way another civilization mapping has clouds or surveying pulsars might stumble across the signal.
It's entirely possible a civilization only broadcasts on sub-etha quantum blockchain because they're only interested in other civilizations with that same technology. It's pointless to wonder about them. They might as well not exist as far as we're concerned. You might as well try to deduce the mating habits of unicorn dragons. They have the same level of influence on humanity as the sub-etha quantum blockchain aliens.
Well, that and [shared sensory experiences] just [feel/digest/reflect] better when they’re transmitted via EM. [untranslatable concept] gives a more accurate, high-fidelity reproduction, sure, but I have always found the EM distortion pleasing to the [untranslatable sensory apparatus].
We haven't abandoned it entirely, we've just started ignoring it and let the parasites fill it up with spam.
If humanity is typical of civilizations, I'd expect the EM spectrum near more advanced civilizations to be buzzing with ads, scams, and malware--most of which is ignored by that civilization.
They haven't said hi because our broadcasts are caught in their spam filer, and we don't know about their spam because it's down out by their star.
It works the other way too: Back when we were single celled organisms, we used to communicate with chemical markers. Now that we're bigger, we mostly ignore that space because our immune systems (read: spam filter) let us get away with that ignorance (mostly).
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.
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.
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.
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.
Definitely yeah
To address your other points,
"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."
Depending on how far you go back yes they would. Most communications today happens in the same frequency ranges they did decades ago. UHF is UHF.
You bring up Enigma. I'm confident if Alan Turing were scanning the airwaves and heard a modern encrypted radio transmission he would immediately determine it was man made and some type of communication. He wouldn't have any hope of decrypting the signal or analyzing the packet structure. The mathematical theory behind modern encryption didn't exist yet let alone the compute power needed to crack it.
"Knowing the popular protocols is an advantage you wouldn't have with "alien communication"."
Normally projects like SETI will look for patterns and structure in the signals they detect. Nature can create some very complex transmissions and it can also create some very regular ones that are simple. But you rarely see both complexity and structure in a signal that isn't man made.
see https://www.itu.int/itunews/manager/display.asp?lang=en&year...
To this extent, there are methods to reliably detect signals 12dB under the noise floor, and as I said this is an area of active research and militaries are probably even further ahead.
Though, if I am not mistaken, the laws of super-sampling hold in this case, and SNR is only improved by O(sqrt(N)) for N samples, so this approach will have practical limits as one has to place a very large number of receivers in range of the emitter (or do auto-correlations over a very long time window), with enough separation to make sure the noise isn't correlated anymore, if looking for a signal deep below the noise floor.
The idea is to entangle all the photons of a star? All the photons in a narrow band?
From another star you can not magically distinguish the entangled photons. You can only make some measurements, and compare it with the measurements of the photons are entangled with, and get some correlations.
For example, you can create a pair of entangled photons in A, send one of them to B. In B the other person/alien can "transfer" the entanglement to a thermal photon from B and send it to A. Now in A you can measure the polarization of the photon you saved and the photon you received from B. Depending of how the other person/alien "transferred" the entanglement, you will get the same or opposite results when you measure the polarizations. So B can use "same" or "opposite" to transmit a bit of information to you.
The difficult part is to pick the correct photon in with a star making a gazillion of photons in the background.
You can create a gazillion of pairs of photons in A and send one half of each pair to B and get later the photon form B. But you must match exactly each received photon with the correct photon of the other half of the pair that you stored. Matching the wrong photon will produce only random noise.
IIUC the idea is that B will not entangle one photon but a gazillion of photons. It is possible to create in B an entangled state where the photon stored in A has the same or the opposite polarization of a gazillion of photons in B and send them. So now it would be easier to pick one of them.
The problem is that someone E in the middle can also look at the photons. Without the photon stored in A, the other person E can only measure random noise, it's impossible to know if B was transmitting "same" or "opposite". The problem is that the intermediate person E will see that in the polarizer all the photons pass or not pass together, never 10% of them pass and the other 90% don't pass.
The intermediate person E will see that half of the time all the photons pass and half of the time all the photons don't pass. This is a clear sign that the photons are entangled. So the secrecy of the quantum communication will be broken, in spite the content will never be discovered.
Not really related to what you have commented, but I wanted to mention it:
Back in Earth, our communication protocols usually have lots of redundancy. Whatever redundancy you can get into the channel, it usually gets inserted at whatever cost it takes - slowing down things a bit here and there - but ensuring a proper message gets to arrive to the other side (at the receiver).
I'm far (FAR) away from trying to sketch here an interstellar quantum comms protocol, but I find certain that if there aliens out there deploying quantum networks, they almost certainly will have redundancy at the level required (to overcome entropy), to get proper messaging in the used channel.
Also, in comparison, the Sun has 3e26 Watts. That's distributed in the full spectrum, and the laser has a very narrow bandwidth. I can't find the exact number now, but from https://en.wikipedia.org/wiki/Laser_linewidth my guess is that it's 1/100000 of the energy is in the same band of the laser, that is 3e20Watts. Let's remove a few zeros to be sure, like 6 zeros, so my guess is something like 3e14Watts.
Comparing the guess of 3e14Watts of the Sun to the 7e6Watts of the laser. So it's not only difficult to see even a photon, there is a lot of noise in the background. I've measured signals like 1/100 of the noise level using a lock-in amplifier, and I think 1/1000 is possible, but 1/100.000.000 looks very difficult.
And now we must consider the quantum part, that is the interesting part of the post. If you generate a lot of pairs of entangled photons, after the trip you must match the photon that traveled with the photon you keep at home.
If you pick the right photon to compare, you theoretically get 100% of agreement, but my guess is that in a lab you will get 90% or less. After an interstellar trip, I'd be happy to get a 1% of correlation, and use a lot of redundancy and error correcting codes to fix it.
The problem is if you pick the wrong photon. You get perfect random noise. Absolutely no information. You can't fix it with redundancy. And with interstellar distances, you must generate a really huge number of photons just to be able to detect a photon in the other side of the communication.
how do you know it's communication?
Anyway, I expect a big variation of traffic. Interstellar communication is (probably) expensive, so I don't expect them to just have a steady communication rate.
Sites here on Earth have a strong weekly variation. Weekends have a different amount of traffic than the rest of the week. It's very regular, so it may be confused with a natural thing, like the little green men in https://en.wikipedia.org/wiki/Pulsar . For short trips, they may use the same week in both stars, that will be weird and noticeable. For long settlements, they will probably use a different local definition.
(I've never seen a monthly variation, except in my bank account.)
Websites have a strong annual variation. Nobody studies math on Christmas! I expect both stars to have their own local version of New-Year/Christmas/Thanksgiving or whatever holiday is popular in your country, that may be confused with a natural phenomena. But I expect that someone with family in both sides will send more messages in the special days in the other star. Even if the lag is 4 years, your parents will never forgive you if you don't send a message on their birthdays and favorite holiday.
Or place an entangled particle emitter between you
I mean, that's part of what makes them advanced civilizations.
Could have been said in the 1800's about why we'd never have quantum computers.
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.
but what if causality it actually isn't a certainty in some contexts? Tadah..you would get ala "FTL" comms enabled.
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_ano...
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.
I can think of two ways in which one would still be limited though. First is that one is limited to dragging signals only as far back as when the necessary machinery was first put in place. This is analog to the limitation of the wormhole time travel hack where you accelerate one close to c, then slow it back down and put it in place again to increase the distance in time to the other end that was stationary the whole time. But perhaps even worse would be the hard limits on how much this could be used before the whole apparatus itself turns into a black hole by the sheer energy being sent back from the far future. it would be like a time lense effectively. Or less spectacularly, it might just get fried. Or perhaps a failsafe would just dump the signal before things get critical. In any case, there would be a limit to how much or from how far in the future one could use such a thing, but other than that it should work, right?
He definitely comes off as slightly off-putting.
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.
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]
Is there a way you could implement this phenomenon in software/hardware and use it as a next secure channel for communication?
if the technology described in the paper actually exists, it would be far away from our current understanding of the reality.
Presumably, even these supposed aliens would have been relatively evolutionarily young once too.
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
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
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.
There's a theorem in QM the guarantees that you can't use measurements on entangled systems to communicate:
If entanglement allowed FTL communication you'd see high-frequency traders already using it!
I have two cards, a red card and a blue card. I have only one of each. I put each into a totally opaque envelope. I have created an entangled pair.
I give you an envelope and you pay SpaceX a few million dollars for a trip to Mars. You have an equal probability of having a red or blue card in your envelope.
Once you settle in on Mars and recover a bit from bone and muscle density loss from six months in zero-g you open your envelope. You have the red card. You've just measured the state of the entangled pair.
You instantly know I have the blue card but your measurement didn't cause some FTL communication. Because our entangled pair had exclusive states you gain some instant knowledge of my envelope contents. While that's a cool effect it still required classical slower-than-light transmission of the envelope. I also have no knowledge that you opened your envelope until I receive your classical communication saying so.
Even if you were just across the room the information about the color of your card would still only travel at the speed of light. Even though you could instantly know the state of my card once you know yours you can only communicate that knowledge to me at the speed of light.
Orson Scott Card is personally responsible for weaponizing "cancel culture" to cancel and outlaw same sex marriages, so he fully deserves to be just as canceled himself for being a hateful bigot, as he would cancel and destroy other people's families for simply loving someone of the same sex.
And Orson Scott Card certainly doesn't deserve credit for an original idea and term coined by a great open minded pioneering feminist science fiction author, Ursula K Le Guin.
https://en.wikipedia.org/wiki/Ursula_K._Le_Guin#Gender_and_s...
>Gender and sexuality are prominent themes in a number of Le Guin's works. The Left Hand of Darkness, published in 1969, was among the first books in the genre now known as feminist science fiction, and is the most famous examination of androgyny in science fiction.
https://www.verbicidemagazine.com/2013/11/07/homophobia-quot...
>“Laws against homosexual behavior should remain on the books, not to be indiscriminately enforced against anyone who happens to be caught violating them, but to be used when necessary to send a clear message that those who flagrantly violate society’s regulation of sexual behavior cannot be permitted to remain as acceptable, equal citizens within that society.” -“The Hypocrites of Homosexuality,” in Sunstone magazine, 1990 (source)
https://en.wikipedia.org/wiki/Orson_Scott_Card#Homosexuality...
>Card has publicly declared his support of laws against homosexual activity and same-sex marriage. Card's 1990 essay "A Changed Man: The Hypocrites of Homosexuality" was first published in Sunstone and republished in his collection of non-fiction essays, A Storyteller in Zion. In the essay, he wrote in favor of laws against homosexual behavior to discourage the acceptance of homosexual people. He said laws against homosexual acts would encourage communities to trust the government to support traditional "marriage and family relationships." Card also stated in a 2004 column that the development of homosexuality has environmental factors that can include abuse. In May 2013, Card wrote that since 2003, when the US Supreme Court had ruled those laws unconstitutional, he has "no interest in criminalizing homosexual acts". Responding to public criticism of the 1990 essay, Card stated since he received criticism for being both homophobic and for "being too supportive of homosexuality", he considered himself as taking a middle way "which condemns the sin but loves the sinner".
Stop Saying You “Love the Sinner; Hate the Sin”
https://redeeminggod.com/love-the-sinner-hate-the-sin/
>The simple fact that we label the person we are talking about as a “sinner” indicates that we do not have love for them in the first place.
>Why do we have to “hate” anything?
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.
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?
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
[1]https://en.wikipedia.org/wiki/Tests_of_special_relativity
I'm not saying that relativity is wrong. It's correct because it clearly aligns with our observations and predicts many things.
But here's the problem: we don't know what space and time are, in the physical sense. We don't know what they're made of. We don't know how malleable they are. It might well be the case that relativity is just one of the parts of a bigger "theory of everything" that does in fact allow FTL travel and/or communication. There were links to papers here on HN how a warp drive is possible without breaking relativity, by making space "flow around" a bubble containing your spaceship instead of propelling the ship itself. Relativity also doesn't forbid almost-Stargate-style traversable wormholes — we just don't know how to make one and most probably don't have enough energy even if we did.
There's no evidence of that, though. Even gravity was recently proven to be limited to the speed of light. In prior cases, observable anomalies suggested fundamental flaws in existing models, and that eventually led to better theories and more accurate models. While it's obvious relativity is incomplete in its incompatibility with quantum mechanics, there is no evidence that the speed of light is variant, or that FTL communication is possible.
So chances are that even if an Alcubierre drive were possible, at best it would allow travel at or near the speed of light, but not more. Same with wormholes. Same with everything.
And then you have the Fermi Paradox. If we're not alone in the universe, then all it takes is for one civilization to discover FTL and colonize or mine a significant enough amount of the galaxy to be noticeable. We're still burning dinosaur carcasses for heat and we've got theoretical models and math, surely someone a million years ahead of us should have expanded into a galactic empire by now.
So (setting aside the countless other solutions to the Fermi Paradox) two possibilites remain - FTL cannot exist, or it's so expensive no civilization has ever bothered.
And we're back to square one, the question of debate. The only reason to believe FTL is possible is a desire to live in a science fiction universe. It's a religious question, a matter of faith, you either believe it or you don't. These discussions always go in circles (fun, but unproductive recursion nonetheless) because one can't really debate faith versus science.
Or yeah, maybe he just finished Remembrance of Earth's Past
[0]: https://en.wikipedia.org/wiki/Terry_Rudolph
[1]: https://www.researchgate.net/scientific-contributions/Terry-...
Terry is also the grandson of Schrodinger!
Perhaps.