Home > My Fiction, Science > Quantum teleportation revisit: Now with wormholes!

Quantum teleportation revisit: Now with wormholes!

Six years ago, I wrote a couple of posts on this blog musing about the physics behind quantum teleportation — first proposing a model in which quantum entanglement could resolve the philosophical condundrum of whether continuity of self could be maintained, then getting into some of the practical limitations that made quantum teleportation of macroscopic objects or people unlikely to be feasible. I recently came upon an article that offers a potential new angle, basically combining the idea of quantum teleportation with the idea of a wormhole.

The article, “Newfound Wormhole Allows Information to Escape Black Holes” by Natalie Wolchover, was published in Quanta Magazine on October 23, 2017. It’s talking about a theoretical model devised by Ping Gao, Daniel Jafferis, and Aron C. Wall, a way that a stable wormhole could exist without needing some kind of exotic matter with arbitrary and probably physically unattainable properties in order to keep it open. Normally, a wormhole’s interior “walls” would attract each other gravitationally, causing it to instantly pinch off into two black holes, unless you could line them with some kind of magic substance that generated negative energy or antigravity, like shoring up a tunnel in the dirt. That’s fine for theory and science fiction, but in practical terms it’s probably impossible.

The new model is based on a theory that’s been around in physics for a few years now, known in short as “ER = EPR” — namely, that wormholes, aka Einstein-Rosen bridges, are effectively equivalent to quantum entanglement between widely separated particles, or Einstein-Podolsky-Rosen pairs. (Podolsky, by the way, is Boris Podolsky, who lived and taught here in Cincinnati from 1935 until his death, and was the graduate advisor to my Uncle Harry. I was really impressed when I learned my uncle was only two degrees of separation from Einstein.) The EPR paradox, which Einstein nicknamed “spooky action at a distance,” is the way that two entangled particles can affect each other’s states instantaneously over any distance — although in a way that can’t be measured until a light signal is exchanged between them, so it can’t be used to send information faster than light. Anyway, it’s been theorized that there might be some sort of microscopic wormhole or the equivalent between the entangled particles, explaining their connection. Conversely, the two mouths of a wormhole of any size could be treated as entangled particles in a sense. What the authors of this new paper found was that if the mouths of a wormhole were created in a way that caused them to be quantum-entangled — for instance, if one of them were a black hole that was created out of Hawking radiation emitted from another black hole (it’s complicated), so that one was a direct outgrowth of the other on a quantum level — then the entanglement of the two black holes/mouths would create, in the words of the paper’s abstract, “a quantum matter stress tensor with negative average null energy, whose gravitational backreaction renders the Einstein-Rosen bridge traversable.” In other words, you don’t need exotic matter to shore up the wormhole interior, you just need a quantum feedback loop between the two ends.

Now, the reason for all this theoretical work isn’t actually about inventing teleportation or interstellar travel. It’s more driven by a strictly theoretical concern, the effort to explain the black hole information paradox. Conservation of energy says that the total amount of energy in a closed system can’t be increased or decreased. Information is energy, and the universe is a closed system, so the total amount of information in the universe should be constant. But if information that falls into a black hole is lost forever, then conservation is violated. So for decades, physicists (notably Stephen Hawking) have been exploring the question of whether it’s possible to get information back out of a black hole, and if so, how. This paper was an attempt to resolve that question. A traversable wormhole spinning off from a black hole provides a way for information to leave the interior of the black hole, resolving the paradox.

I only skimmed the actual paper, whose physics and math are way beyond me, but it says that this kind of entangled wormhole would only be open for a very brief time before collapsing. Still, in theory, it could be traversable at least once, which is better than previous models where the collapse was instantaneous. And if that much progress has been made, maybe there’s a way to refine the theory to keep the wormhole open longer.

There’s a catch, though. Physical law still precludes information from traveling faster than light. As with quantum teleportation, there is an instantaneous exchange of information between the two ends, but that information remains in a latent, unmeasurable state until a lightspeed signal can travel from the transmitting end to the receiving end. So a wormhole like this, if one could be created and extended over interstellar distances, would not allow instantaneous travel. A ship flying into one end of the wormhole would essentially cease to exist until the lightspeed signal could reach the other end, whereupon it would emerge at long last.

However — and this is the part that I thought of myself as an interesting possibility for fiction — this does mean that the ship would be effectively traveling at the speed of light. That in itself is a really big deal. In a physically realistic SF universe, it would take an infinite amount of energy and time to accelerate to the speed of light, and once you got fairly close to the speed of light, the hazards from oncoming space dust and blueshifted radiation would get more and more deadly. So as a rule, starships would have to stay at sublight speeds. In my original fiction I’ve posited starships hitting 80 or 90 percent of c, but even that is overly optimistic. So in a universe where starships would otherwise be limited to, say, 30 to 50 percent of lightspeed, imagine how remarkable it would be to have a wormhole transit system that would let a starship travel at exactly the speed of light. Moreover, the trip would be instantaneous from the traveler’s perspective, since they’d basically be suspended in nonexistence until the lightspeed signal arrived to “unlock” the wormhole exit. It’s not FTL, but it’s L, and that alone would be a damned useful stardrive. You could get from Earth to Alpha Centauri in just 4.3 years, and the trip would take no time at all from your perspective, except for travel time between planet and wormhole mouth. You’d be nearly 9 years younger than your peers when you got home — assuming the wormhole could be kept open or a second temporary wormhole could be generated the other way — but that’s better than being 2 or 3 decades younger. Short of FTL, it’s the most convenient, no-fuss means of interstellar travel I can think of.

Or, looked at another way, it’s a method for interstellar quantum teleportation that avoids all the scanning/transmission obstacles and impracticalities I talked about in my second 2011 post on the subject. No need to use a technological device to scan a body with a level of detail that would destroy it, then transmit a prohibitively huge amount of data that might take millennia to send in full. You just pop someone into one end of a wormhole and make sure the handshake signal is transmitted strongly enough to reach the other end. I’ve long felt that wormhole-based teleportation would be a more sensible approach than the disintegration-based kind anyway. Although we’re technically talking about black holes, so it wouldn’t be the sort of thing where you could just stand on a platform in your shirtsleeves and end up somewhere else. Also, there might be a little problem with getting torn apart by tidal stresses at either end. I’m not sure the paper addresses that.

This idea could be very useful for a hard-SF universe. My problem is that the universes I have established are a little less hard than that, though, since I tend to like working in universes with FTL travel of one sort or another. But maybe some idea will come to me for a future story. And maybe some other writer will read this and get an idea. We’re all in this together, and any worthwhile SF concept can inspire multiple very different stories.

  1. December 13, 2017 at 1:04 pm

    The end result of this type of teleportation system is quite like that used in Stephen Baxter’s “Manifold” universe. The core mechanism seems to be different, though also based on quantum physics, but the overall effect is strikingly similar–lightspeed teleporation over interstellar distances. The implications of this mode of travel in a story would also be similar.

    Having teleportation, that’s instantaneous for the people using it, without all the nasty relativistic effects of travelling at *almost* lightspeed, would be incredible. (It would also mean you wouldn’t have the problem of terrorists crashing relativistic vehicles into your planet, since there would be no incentive to invent them in the first place.) This still wouldn’t be the kind of interstellar trip you’d take casually, but it’s much better than the alternative. It would also eliminate the possibility for the formation of closed timelike curves, since you never travel FTL relative to an outside observer. (Of course, that would also eliminate the possibility of using a wormhole to even peek into the past, as they are in the “The Light of Other Days”.)

    Interplanetary travel would be trivial, however, since it would only take a few hours to reach even the furthest planet, and only a single year to reach the Oort Cloud. Also, the rocket equation wouldn’t have a stranglehold on one’s capabilities for long-distance travel, especially if one starts their journey from space.

    I’m not going to lie–this post has given me some ideas.

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