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posted by charon on Thursday May 18, @11:53AM   Printer-friendly
from the band-name-of-the-week dept.

Futurism reports:

For the first time in the history of quantum mechanics, scientists have been able to transmit a black and white image without having to send any physical particles. The phenomenon can be explained using the Zeno effect, the same effect that explains that movement itself is impossible.

The journal article is in Proceedings of the National Academy of Sciences of the United States of America (DOI: 10.1073/pnas.1614560114)

Wikipedia has an article about the quantum Zeno effect.

Related stories:
Physicists Break Distance Record for Quantum Teleportation
First Covert Communication System with Lasers
Long-Range Secure Quantum Communication System Developed
China's "Quantum-Enabled Satellite" Launches
How to Outwit Noise in Quantum Communication


Original Submission

Related Stories

First Covert Communication System with Lasers 13 comments

Scientists develop first completely covert communication system with lasers:

As computing power continues to increase, previously unbreakable forms of encryption have crumbled. Now, though, we appear to be on the verge of what may be truly unbreakable quantum encryption. It's possible in the not too distant future no one will be able to spy on a message secured with these advanced methods no matter how long they hammer at it. Researchers are now looking to take things one step further and completely camouflage a message so no one even knows that a message was sent in the first place. If you can't even risk an eavesdropper knowing that a message has been sent, let alone what it says, you need a covert communication system. That's the idea at the heart of a new experiment conducted at the University of Massachusetts. Researchers there have developed a method of using photons to make a message invisible to everyone but the intended recipient.

The covert system relies on a technique called pulse position modulation, which is actually much more simple than you'd expect. It involves dividing a second, minute, or other unit of time into discrete bands, each of which correspond to a different letter or symbol. This code would have to be shared with the intended recipient ahead of time, which is perhaps the most notable flaw with the whole scheme. Once that's done, through, a series of pulses could be delivered like optical Morse code to convey a message.

http://www.extremetech.com/extreme/182142-scientis ts-develop-first-completely-covert-communication-s ystem-with-lasers

http://arxiv.org/abs/1404.7347

Physicists Break Distance Record for Quantum Teleportation 12 comments

Researchers at the National Institute of Standards and Technology (NIST) have "teleported" or transferred quantum information carried in light particles over 100 kilometers (km) of optical fiber, four times farther than the previous record.

The experiment confirmed that quantum communication is feasible over long distances in fiber. Other research groups have teleported quantum information over longer distances in free space, but the ability to do so over conventional fiber-optic lines offers more flexibility for network design.
...
"Only about 1 percent of photons make it all the way through 100 km of fiber," NIST's Marty Stevens says. "We never could have done this experiment without these new detectors, which can measure this incredibly weak signal."

Until now, so much quantum data was lost in fiber that transmission rates and distances were low. The new NTT/NIST teleportation technique could be used to make devices called quantum repeaters that could resend data periodically in order to extend network reach, perhaps enough to eventually build a "quantum internet." Previously, researchers thought quantum repeaters might need to rely on atoms or other matter, instead of light, a difficult engineering challenge that would also slow down transmission.

Quantum teleportation over 100 km of fiber using highly efficient superconducting nanowire single-photon detectors


Original Submission

Long-Range Secure Quantum Communication System Developed 8 comments

A group of scientists from ITMO University in Saint Petersburg, Russia has developed a novel approach to the construction of quantum communication systems for secure data exchange. The experimental device based on the results of the research is capable of transmitting single-photon quantum signals across distances of 250 kilometers or more, which is on par with other cutting edge analogues. The research paper was published in the Optics Express journal.

Information security is becoming more and more of a critical issue not only for large companies, banks and defense enterprises, but even for small businesses and individual users. However, the data encryption algorithms we currently use for protecting our data are imperfect -- in the long-term, their logic can be cracked. Regardless of how complex and intricate the algorithm is, getting round it is just the matter of time.

Contrary to algorithm-based encryption, systems that protect information by making use of the fundamental laws of quantum physics, can make data transmission completely immune to hacker attacks in the future. Information in a quantum channel is carried by single photons that change irreversibly once an eavesdropper attempts to intercept them. Therefore, the legitimate users will instantly know about any kind of intervention.

[...] In order to encode quantum bits in the system, laser radiation is directed into a special device called the electro-optical phase modulator. Inside the modulator the central carrier wave emitted by the laser is split into several independent waves. After the signal is transmitted through the cable, the same splitting occurs on the receiver end. Depending on the relative phase shift of the waves generated by the sender and the receiver, the waves will either enhance or cancel each other. This pattern generated by overlapping wave phases is then converted into the combination of binary digits, 1 and 0, which serves to compile a quantum key.


Original Submission

China's "Quantum-Enabled Satellite" Launches 18 comments

China has launched a satellite that will beam entangled photons to base stations on Earth:

China has successfully launched the world's first quantum-enabled satellite, state media said. It was carried on a rocket which blasted off from the Jiuquan Satellite Launch Centre in China's north west early on Tuesday. The satellite is named after the ancient Chinese scientist and philosopher Micius. The project tests a technology that could one day offer digital communication that is "hack-proof". But even if it succeeds, it is a long way off that goal, and there is some mind-bending physics to get past first.

The satellite will create pairs of so-called entangled photons - tiny sub-atomic particles of light whose properties are dependent on each other - beaming one half of each pair down to base stations in China and Austria. This special kind of laser has several curious properties, one of which is known as "the observer effect" - its quantum state cannot be observed without changing it. So, if the satellite were to encode an encryption key in that quantum state, any interception would be obvious. It would also change the key, making it useless.


Original Submission

How to Outwit Noise in Quantum Communication 4 comments

How to reliably transfer quantum information when the connecting channels are impacted by detrimental noise? Scientists at the University of Innsbruck and TU Wien (Vienna) have presented new solutions to this problem.

Nowadays we communicate via radio signals and send electrical pulses through long cables. This could change soon, however: Scientists have been working intensely on developing methods for quantum information transfer. This would enable tap-proof data transfer or, one day, even the linking of quantum computers.

Quantum information transfer requires reliable information transfer from one quantum system to the other, which is extremely difficult to achieve. Independently, two research teams – one at the University of Innsbruck and the other at TU Wien (Vienna) - have now developed a new quantum communication protocol. This protocol enables reliable quantum communication even under the presence of contaminating noise. Both research groups work with the same basic concept: To make the protocol immune to the noise, they add an additional element, a so-called quantum oscillator, at both ends of the quantum channel.

Scientists have conducted quantum communication experiments for a long time. "Researchers presented a quantum teleportation protocol already in the 1990s. It permits transferring the state of one quantum system to another by using optical photons," says Benoit Vermersch, Postdoc in Peter Zoller's group at the University of Innsbruck. This works also over great distances but one has to accept that a lot of the photons are lost and only a tiny fraction reaches the detector.

"Our goal was to find a way to reliably transfer a quantum state from one place to the other without having to do it several times to make it work," explains Peter Rabl from the Atominstitut, TU Wien.


Original Submission

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  • (Score: 2) by Gaaark on Thursday May 18, @12:22PM (2 children)

    by Gaaark (41) on Thursday May 18, @12:22PM (#511652) Homepage Journal

    What the what?

    Gotta go do some reading!

    --
    --- I wish i had a cig for every sig i've ever had: i'd have cancer and wouldn't you feel bad for looking here. ---
    • (Score: 2) by Gaaark on Thursday May 18, @01:06PM (1 child)

      by Gaaark (41) on Thursday May 18, @01:06PM (#511666) Homepage Journal

      Soooo... a watched pot never boils? Essentially?

      ???

      --
      --- I wish i had a cig for every sig i've ever had: i'd have cancer and wouldn't you feel bad for looking here. ---
      • (Score: 0) by Anonymous Coward on Thursday May 18, @03:03PM

        by Anonymous Coward on Thursday May 18, @03:03PM (#511698)

        At least a watched Weeping Angel never moves.

  • (Score: -1, Offtopic) by Anonymous Coward on Thursday May 18, @12:28PM

    by Anonymous Coward on Thursday May 18, @12:28PM (#511657)

    i smuggle lizards in my rectum

  • (Score: 3, Funny) by datapharmer on Thursday May 18, @12:49PM (11 children)

    by datapharmer (2702) on Thursday May 18, @12:49PM (#511665)

    Pictures or it never happened.

    • (Score: 0) by Anonymous Coward on Thursday May 18, @01:07PM (5 children)

      by Anonymous Coward on Thursday May 18, @01:07PM (#511667)

      In the link there is another link to graphs. I clicked it and it asked me for a paid subscription.

      • (Score: 5, Funny) by Nuke on Thursday May 18, @01:20PM (4 children)

        by Nuke (3162) on Thursday May 18, @01:20PM (#511671)

        In the link there is another link to graphs. I clicked it and it asked me for a paid subscription

        Just tell them you sent the money without sending any physical particles.

        • (Score: 2) by kaszz on Thursday May 18, @04:49PM (3 children)

          by kaszz (4211) on Thursday May 18, @04:49PM (#511731) Journal

          Must be like quantum money. You never know how much they are until eyeballs looks into the wallet ;-)

    • (Score: 2) by theluggage on Thursday May 18, @01:37PM (1 child)

      by theluggage (1797) on Thursday May 18, @01:37PM (#511674)

      Pictures or it never happened.

      Is that a genuine request, or a joke about quantum mechanics?

    • (Score: 2) by DeathMonkey on Thursday May 18, @05:27PM (2 children)

      by DeathMonkey (1380) Subscriber Badge on Thursday May 18, @05:27PM (#511748) Journal

      Pictures or it never happened.

      Well, I could show them to you but then we wouldn't be able to find the damn thing!

      • (Score: 2) by bob_super on Thursday May 18, @07:21PM (1 child)

        by bob_super (1357) on Thursday May 18, @07:21PM (#511794)

        If I can observe the position of the picture, it will be moving? I've always wondered about that when watching Harry Potter...

  • (Score: 2, Informative) by butthurt on Thursday May 18, @01:09PM

    by butthurt (6141) on Thursday May 18, @01:09PM (#511669) Journal
  • (Score: 0) by Anonymous Coward on Thursday May 18, @03:25PM (7 children)

    by Anonymous Coward on Thursday May 18, @03:25PM (#511708)

    A lot of users here are going to have to swallow a whole lot of pride. Can you do it? Can you say "I was wrong"?

    • (Score: 0) by Anonymous Coward on Thursday May 18, @03:37PM (6 children)

      by Anonymous Coward on Thursday May 18, @03:37PM (#511711)

      Swallow a whole lot of pride? What did they even say?

      • (Score: 0) by Anonymous Coward on Thursday May 18, @04:06PM (4 children)

        by Anonymous Coward on Thursday May 18, @04:06PM (#511723)

        Started with "quantum entanglement is bogus, they just don't understand simple statistics!" then continued with "sure they're entangled, but you can't transmit anything with it so its just a useless gimmick" along with downplaying quantum computers etc.

        I'm just mouthing off cause I can't stand people who hold to the status quo because anything new and different is scary and can't possibly be right. Many people would weigh in with confident proclamations of this being quackery, so now it would be nice for them to swallow that attitude and realize that maybe they a bit close minded.

        • (Score: 0) by Anonymous Coward on Thursday May 18, @04:56PM (3 children)

          by Anonymous Coward on Thursday May 18, @04:56PM (#511735)

          Quantum entanglement is real and well-established phenomena. However, it is not possible [wikipedia.org] to use it for the transmission of information.

          As for quantum computers, the feasibility and practicality remains to be seen. For the time being, their existence is purely theoretical.

          I'm just mouthing off cause I can't stand people who hold to the status quo because anything new and different is scary and can't possibly be right. Many people would weigh in with confident proclamations of this being quackery, so now it would be nice for them to swallow that attitude and realize that maybe they a bit close minded.

          If your best argument is shaming skeptics, I'd say your failure to convert them to your point of view is entirely your own.

          • (Score: 0) by Anonymous Coward on Thursday May 18, @05:36PM (1 child)

            by Anonymous Coward on Thursday May 18, @05:36PM (#511753)

            I'm just mouthing off cause I can't stand people

            Misanthrope! Back to your Mom's basement, you quantum fanboi!!!

          • (Score: 0) by Anonymous Coward on Friday May 19, @06:16AM

            by Anonymous Coward on Friday May 19, @06:16AM (#512046)

            "If your best argument is shaming skeptics, I'd say your failure to convert them to your point of view is entirely your own."

            Lol, way to promote the age of polarization! I was never looking to "convert" anyone, I just dislike the knee jerk reactions from close minded fools. Such were (and still are, I met a flat earther zomg) the promoters of flat earth theory, earth is the center of the universe, woman was created from a rib of man, we were popped into existence as perfect human beings, etc. etc.

            I'm all for skepticism, just open minded skepticism that realizes our knowledge is not complete. Probably your basic attitude is the problem, everything is black / white, must believe or not. Therefore you throw out arguments cause you're not willing to believe, but all that is being asked is to keep your mind open to the possibilities. Until this article I would have never said there was proof of quantum entanglement information transfer because I had never heard of such proof, but I would have said it might be possible. I guess you're still stuck on your pride ;) And I'm stuck in the same old world where open minded people are derided as fools BY fools :( Making my peace with it hopefully sooner rather than later.

      • (Score: 0) by Anonymous Coward on Thursday May 18, @05:54PM

        by Anonymous Coward on Thursday May 18, @05:54PM (#511762)

        Swallowing large family groups of lions is not recommended, no matter what your position on ghostly action-at-a-distance.

  • (Score: 3, Insightful) by cpghost on Thursday May 18, @03:48PM (8 children)

    by cpghost (4591) on Thursday May 18, @03:48PM (#511716) Homepage

    This gets me thinking that SETI may very well be wasting their time hunting for electromagnetic (radio) signals. Any highly enough developed civilization may eventually switch to Quantum Communications, especially for very long-distance comms, if they could find a way to do it efficiently. Therefore, SETI may currently be hunting for analog modulation in a world full of digital signals, to stretch a metaphor.

    --
    Cordula's Web. http://www.cordula.ws/
    • (Score: 0) by Anonymous Coward on Thursday May 18, @04:08PM (2 children)

      by Anonymous Coward on Thursday May 18, @04:08PM (#511724)

      ok, here's the deal: you give me all your fiber, because you can do quantum communication without it, right? I'm dumb and I can only do it with the fiber, but snce you're not using it, can I have all your fiber?

      • (Score: 0) by Anonymous Coward on Thursday May 18, @04:57PM

        by Anonymous Coward on Thursday May 18, @04:57PM (#511736)

        cpg uses the fiber for classical communication and to stay regular.

      • (Score: 2) by maxwell demon on Thursday May 18, @05:17PM

        by maxwell demon (1608) Subscriber Badge on Thursday May 18, @05:17PM (#511746) Journal

        ok, here's the deal: you give me all your fiber, because you can do quantum communication without it, right?

        Wrong. The funny thing about this counterfactual imaging is that it only works if you could have sent the light. Basically, you are measuring the reflection of light that you didn't send; but you still need to provide all the optics, even though you're not sending light through it. You sort of send "counterfactual light" through it.

        --
        The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 2) by kaszz on Thursday May 18, @04:51PM

      by kaszz (4211) on Thursday May 18, @04:51PM (#511733) Journal

      And it may also send the alphabet soup into the dark.. without any mangling of bits ;-)

    • (Score: 2) by wonkey_monkey on Thursday May 18, @08:03PM (3 children)

      by wonkey_monkey (279) on Thursday May 18, @08:03PM (#511806) Homepage

      Any highly enough developed civilization may eventually switch to Quantum Communications, especially for very long-distance comms, if they could find a way to do it efficiently.

      What do you mean by "quantum communication"? If you mean twiddling one half of an entangled pair to send a message to the other, that can't be done. You've always got to send something from A to B to pass a message.

      --
      systemd is Roko's Basilisk
      • (Score: 2) by JoeMerchant on Friday May 19, @12:25PM (2 children)

        by JoeMerchant (3937) on Friday May 19, @12:25PM (#512137)

        That's what pisses me off about the summary, the summary implies that they are passing a message "without sending particles" - but they're sending single photon waves, so, how is this even impressive? Because they called their photons waves instead of particles?

        I'll start calling Republicans Right Wing instead of Conservative, does that get me a big headline?

        • (Score: 2) by wonkey_monkey on Friday May 19, @09:12PM (1 child)

          by wonkey_monkey (279) on Friday May 19, @09:12PM (#512377) Homepage

          I've yet to find an explanation that is detailed enough to actually be informative, but not so detailed that I'd have no idea what it was talking about.

          Maybe there is no such explanation, of course...

          --
          systemd is Roko's Basilisk
          • (Score: 2) by JoeMerchant on Friday May 19, @09:25PM

            by JoeMerchant (3937) on Friday May 19, @09:25PM (#512387)

            Personally, the whole concept of quantum communication strikes me as useless word games. You have a secret message, the secret travels faster than the speed of light - but just the secret, not the message. Pointless.

  • (Score: 2) by JoeMerchant on Friday May 19, @03:39AM (14 children)

    by JoeMerchant (3937) on Friday May 19, @03:39AM (#511990)

    If this actually works, we will see applications in the arbitrage markets very soon.

    Conversely, if we don't see applications of this in the arbitrage markets, the traders have been unable to replicate the process described in the paper. Frankly, I'm surprised this was published at all instead of being marketed to the trading houses that spend millions on more direct fiber routes to cut communication times for higher profits.

    • (Score: 2) by JoeMerchant on Friday May 19, @03:46AM (2 children)

      by JoeMerchant (3937) on Friday May 19, @03:46AM (#511995)

      Oh, nevermind, they aren't communicating directly, they're hitching a ride on the phase information of a wave instead of a particle. No speed value to traders there.

      To determine whether light appears in a channel, one refers to the amplitude of its wave function. However, in counterfactual communication, information is carried by the phase part of the wave function. Using a single-photon source, we experimentally demonstrate the counterfactual communication and successfully transfer a monochrome bitmap from one location to another by using a nested version of the quantum Zeno effect.

      So, in a normal slide projector, you pass light through a patterned semi-transparent plate and the changes in amplitude of the passing light waves project the image.

      In these guys' version, they're encoding their image information on the phase of single photon waves.

      But, if photons are particles and waves at the same time, are they really communicating "without particles?" It seems to me that ignoring the photon's particle like properties doesn't make them cease to exist.

      • (Score: 2) by FatPhil on Sunday May 21, @09:36AM (1 child)

        by FatPhil (863) <{pc-soylent} {at} {asdf.fi}> on Sunday May 21, @09:36AM (#512946) Homepage
        Perceived amplitude of light is not due to the amplitude of the wave functions, but in the number of equal-amplitude (as per E=hv) wave packets.
        --
        I was worried about my command. I was the scientist of the Holy Ghost.
        • (Score: 2) by JoeMerchant on Sunday May 21, @12:11PM

          by JoeMerchant (3937) on Sunday May 21, @12:11PM (#512984)

          Fun extension: what happens when those wave packets get out of phase with each other?

          Is that dark matter? Are we swimming in a universe of mostly out of phase wave packets, where we only see the ones that have become phase aligned?

    • (Score: 2) by wonkey_monkey on Friday May 19, @09:21PM (10 children)

      by wonkey_monkey (279) on Friday May 19, @09:21PM (#512382) Homepage

      If someone found a way to communicate faster than the speed of light - through entanglement or something else entirely - they'd have a functioning time machine, so the stock markets would soon be a thing of the past.

      --
      systemd is Roko's Basilisk
      • (Score: 2) by wonkey_monkey on Friday May 19, @09:24PM

        by wonkey_monkey (279) on Friday May 19, @09:24PM (#512386) Homepage

        I should add, that "through entanglement" bit was entirely speculative. It's almost certainly not possible and certainly impossible given current understanding.

        --
        systemd is Roko's Basilisk
      • (Score: 2) by JoeMerchant on Friday May 19, @09:31PM (8 children)

        by JoeMerchant (3937) on Friday May 19, @09:31PM (#512389)

        Simple communication faster than the speed of light isn't a time machine per-se. It gets you ahead of the light speed propagation of information, but in near-earth areas (the only areas with information relevant to the stock market that are presently reachable by man-made devices), the difference is seconds - far less than the affect that the telegraph had on trading when it came into play - it won't collapse the market, but it would turn certain high speed trading operations on their heads.

        Actually, thinking about options pricing models, they use techniques quite similar to quantum communication tools... wouldn't it be weird if the two could be fused into a more powerful (profitable) combined strategy?

        • (Score: 2) by wonkey_monkey on Saturday May 20, @12:18AM (7 children)

          by wonkey_monkey (279) on Saturday May 20, @12:18AM (#512451) Homepage

          Simple communication faster than the speed of light isn't a time machine per-se.

          Any faster-than-light communication is ambiguous as to whether it's going backwards or forwards in time - in some reference frames it will be forwards, in some it will be backwards. All you have to do is to get your transmitter/receiver into the right frame(s) and you can send messages back to last Tuesday.

          --
          systemd is Roko's Basilisk
          • (Score: 2) by JoeMerchant on Saturday May 20, @01:00AM (6 children)

            by JoeMerchant (3937) on Saturday May 20, @01:00AM (#512465)

            All you have to do is to get your transmitter/receiver into the right frame(s) and you can send messages back to last Tuesday.

            If you're limited to the neighborhood of Earth, you'll never get back to last Tuesday. You might receive a message from "5 seconds in the future" about a distant star going Nova, but anything that happens on Earth propagates away from Earth at SOL, instantly communicating that back is just repeating what you already knew, not working forward in time.

            Instant communication would be a great Distant Early Warning system, but you're not going to get messages about where you are from the future.

            Now, since instant quantum communication is "off the table" anyway according to current widely accepted (made up) theories, you can as easily posit weirder particles that travel in retrograde time and then try to harness those to talk to last Tuesday about tonight's lottery numbers. The trick is in analyzing the LHC data to find evidence of these retrograde time particles when none of their sensor arrays have been designed to look for them.

            • (Score: 2) by wonkey_monkey on Saturday May 20, @01:03PM (5 children)

              by wonkey_monkey (279) on Saturday May 20, @01:03PM (#512602) Homepage

              Instant communication would be a great Distant Early Warning system, but you're not going to get messages about where you are from the future.

              Yes, you can, because "instant" is not well-defined. One person's "instant" is another's "into the future" and another's "back in time." All you have to do is set a chain of "instant" communication machines in the right reference frames and they can bounce messages back and forth as far back in time as you like.

              Thanks to relativity, if it's 10am on Earth and 9am on a travelling spaceship (from the perspective of Earth), it can also be 9am on the travelling spaceship and 8am on Earth (from the perspective of the spaceship). So Earth sends the "instant" message at 10am Earth time, it's received at 9am ship time, immediately sent back out and arrives on Earth at 8am.

              --
              systemd is Roko's Basilisk
              • (Score: 2) by JoeMerchant on Saturday May 20, @05:18PM

                by JoeMerchant (3937) on Saturday May 20, @05:18PM (#512651)

                Sounds wonky to me, and since it's based on things that are "impossible" in currently demonstrated theory, it's all just as verifiable and important as the turtles (all the way down.)

              • (Score: 2) by JoeMerchant on Saturday May 20, @11:29PM (3 children)

                by JoeMerchant (3937) on Saturday May 20, @11:29PM (#512787)

                So, I just want to draw this one out, on phosphor screen as it were:

                Assuming that "spooky action at a distance" happens "instantaneously" (whatever that means), I'm going to define 0:00 as "now" for two frames, A and B which are located 1 light hour apart, stationary with respect to each other.

                At 1:00, the light from A at 0:00 is reaching B, and the light from B at 0:00 is reaching A. If spooky action at a distance could carry information, it could carry that light picture from A to B and B could see what A looks like at 0:00 right away at 0:00. No amount of bouncing back and forth will ever get any information about what A looks like at 1:00 back to A before 1:00. Draw in C and D, make it a 3D system, same thing applies, information about A at 1:00 will not reach anywhere before 1:00.

                If you want to include relativistic motion, B could be orbiting a black hole at close proximity and be experiencing 50% time dilation. Light from A at 0:00 now reaches B at B's concept of 0:30 local time, but C - located just to the side of the black hole and not experiencing significant time dilation receives that A 0:00 light at C 1:00 perceived time. Just because B is only up to 0:30 local time doesn't give anyone "access to the future" - it just means that B is aging more slowly. A 1:00 information could be "spooky transmitted" to B, and in B's frame of reference it's only 0:30, but when B transmits that information back to A, it's still going to be A 1:00 + transmission delays, the spooky information transfer doesn't reach back in time. Or does it? This is all made up, anyway, no accepted theories believe in "spooky transmission of information," so, maybe we entangle some particles, split them up, put some in B and they "age" at half rate, then when A does spooky transmission, it reaches B at the "age matched" time - but, wait, B 1:00 is A 2:00, so, again, A can't get information about A 1:00 that way until A 2:00. Try it in reverse, now B's 1:00 information is pushed out to "time matched" A at 1:00, woo hoo, you've put information into the past because at A 1:00 B is only at 0:30, bounce that around a contrived chain and then pop the information across a conventional light speed communication channel and you've got information about the future of B back in B, but this is only assuming that the "instant communication" particles are affected by time dilation and then "instantly communicate" backwards and forwards in the instant time frame... seems doubly contrived.

                Just think like Hollywood: time travel just works, now write a story around it and the consequences, don't get hung up in the details - be like Mary Shelly: "reverse the poles, minus to plus, plus to minus - Eeeeeeeeeeeeee its Aliiiiiiiiiiiive!"

                • (Score: 2) by wonkey_monkey on Sunday May 21, @10:37AM (2 children)

                  by wonkey_monkey (279) on Sunday May 21, @10:37AM (#512971) Homepage

                  Sticking close to a black hole to keep your clock running slow is general relativity, not special relativity, and is not symmetrical (A sees B run slow, B sees A run fast).

                  If there is just simple relative motion, then it's as I described (A sees B run slow, B sees A run slow). The line of "now" from A intersects B at a certain point in B's time, but B's line of "now" from that point in time has a different angle to A's, and so intersects A at an earlier time (if distance is increasing; if decreasing, repeated messages end up in the future).

                  --
                  systemd is Roko's Basilisk
                  • (Score: 2) by JoeMerchant on Sunday May 21, @12:08PM (1 child)

                    by JoeMerchant (3937) on Sunday May 21, @12:08PM (#512983)

                    The "simple relative motion" example always tossed around on pop-sci shows is: A is A "stationary". B accelerates away from A to relativistic speed, now B runs slow. B keeps on going in a loop at relativistic speeds (lots of acceleration there), then returns to A - the "interstellar traveler" from "B ship" has aged 1 year, but his family and friends on A have all been dead for a thousand. What I've never seen the pop-sci shows get into is "C ship" that tears off in the opposite direction of B, now C is moving even closer to the speed of light, relative to B, but if they both arrive back at A simultaneously, A is aged the same for both of them, but why are they the same age as each other?

                    I still love the concept that the photons leaving the surface of stars 10 billion years ago are arriving in our telescopes "instantly," unaged since they were emitted.

                    • (Score: 2) by wonkey_monkey on Sunday May 21, @06:11PM

                      by wonkey_monkey (279) on Sunday May 21, @06:11PM (#513087) Homepage

                      B and the C are the same age because they've undergone identical accelerations. The one who ages the most is the one who took the straightest path from launch to meet-up - in this case A, because he didn't accelerate at all, he just let "meet-up" come to him. The other two took wiggly paths, but identically wiggly, so the amount of time experienced by themselves on their trip is the same.

                      During the constant relative motion parts (among all three of them), they all see the others' clocks runs slow. But during accelerations towards each other, there are times when others' clocks run fast.

                      I still love the concept that the photons leaving the surface of stars 10 billion years ago are arriving in our telescopes "instantly," unaged since they were emitted.

                      Kind of... but the standard physicist answer to this is that photons don't have reference frames, so you can't consider anything from their "point of view" - they don't have one. The math does pretty clearly point in that direction, though.

                      --
                      systemd is Roko's Basilisk
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