Communicating with distant space-craft in our solar system is cumbersome and time consuming, because the distances are huge and signals can’t be sent faster than the speed-of-light. A signal from Earth can take from three to twenty-two minutes to reach Mars, for example, depending on the position of the two planets in their orbits. Worse, the sun blocks signals when it lies in their path.
As we explore farther from the Earth beyond Mars, these delays and blockages will start to really annoy us. The need to develop a technology for instantaneous communication that can penetrate or bypass the sun will become compelling.
Quantum particles are known for their ability to “tunnel” through or ignore barriers, as they clearly do in double-slit experiments, where electrons, for example, are fired one at a time and strike impossible locations. So, looking to a quantum process for signaling might be a good place to start to find solutions to our long-range communication problems.
If we are able to develop quantum signaling over solar-system-scale distances, we might discover later that by adding certain tweaks and modifications, we can render the sun transparent to our evolving planet-to-planet communications network. Indeed, the sun is transparent to neutrinos, the lightest (least massive) particles known. In 2012, scientists showed they could use neutrinos to send a meaningful signal through materials that block or attenuate most other kinds of subatomic particles.
But this article is about faster than light (FTL) communication. Making the sun transparent to inter-planetary signaling is best left for another article.
Quantum entanglement is the only phenomenon known where information seems to pass instantly between widely placed objects. But because the information is generated randomly, and because it is transferred between objects that are, themselves, traveling at speeds at or below the speed-of-light, it seems clear to most physicists that faster-than-light (FTL) messaging can’t come from entanglement, certainly, or any other process; especially once we accept Einstein’s theory of a cosmic speed-limit.
Proposals for FTL communications based on technologies rooted in the quantum process of entanglement are usually dismissed as crack-pot engineering, because they seem to be built on fundamental misunderstandings of the phenomenon. Nevertheless, there may be ways to do it, possibly. And the country that develops the technology first will accrue advantages for their space exploration programs.
In this essay I hope to explain how FTL messaging might work, put my ideas into a blog-bottle and throw it into the vast cyber-ocean. Yes, the chances are almost zero that the right people will find my bottle, but I don’t care. For me, it’s about the fun of sharing something interesting and trying to explain it to whoever will listen. Maybe a wandering NSA bot will detect my post and shuffle it up the chain-of-command for a human to review. What are the odds? Not good, probably.
Anyway, two serious obstacles must be overcome to communicate instantaneously over astronomical distances using quantum entanglement. The first is the problem of creating a purposeful signal. (To learn more about this problem and the physics behind entanglement please click on the link in this sentence.)
The second problem is how to create the architectural space for sending a signal instantly to a distant observer. Knowledgeable people who have written about this subject have agreed that both obstacles seem to be insurmountable.
Why? It’s because the states of an entangled pair of subatomic particles are not determined until one of the particles is measured. The states can’t be forced; they can only be discovered, and only after they are created by a measurement. Once one particle’s state is created (randomly) through the mechanism of a measurement, the information is transferred to the entangled partner-particle instantly, yes, but the particles themselves are traveling at the speed-of-light or less. The randomly generated states carried by these entangled particles aren’t going anywhere for very long faster than the speed-limit of light.
How can these difficulties be overcome?
Although the architectural problem is the most interesting, let’s address the purposeful-signal problem first. A good analogy to aid understanding might be that of an old-fashioned typewriter. Each key on a typewriter, when pressed, delivers a unique piece of information (a letter of the alphabet) onto a piece of paper. A person standing nearby can read the message instantly. Fair enough.
Imagine setting up a device which emits entangled pairs of photons; imagine rigging the emissions so that half the photons, when measured later, will be polarized one way; half the other. We can’t know which photons will display which state, but we can predict the overall ratio of the two polarities from our “weighted” emitter. Call the 50/50 ratio, letter “A”. Now imagine configuring another emitter-system to display three-fourths of the photons polarized one way; one-fourth another way, after measurement. Call the 75/25 ratio, letter “B”. If we could construct rigged or weighted emitters like these, then half of the FTL communication problem would be solved.
Although we could never know the state of any single particle until after a measurement, we could predict statistically the polarization states of a large number sent from any of the unique emitter-configurations we designed. This capability would then allow us to build our typewriter keyboard by setting up photon emitters with enough statistical variation in their emission patterns to differentiate them into as many identifiable signatures as needed—perhaps an entire alphabet or—maybe better—some other symbolic coding array—a binary on-off signaling system comes to mind. In that case, only one configuration of emitter would be required, but designers would need to solve other technical problems involving rapid signal sequencing.
To send a purposeful-signal, engineers would select an array of emitters and rapid-fire photons from them. If they selected an “A” (or perhaps an “on”) emitter, fifty percent of the photons would register as being in a particular polarization state after they were measured. If they chose “B”, seventy-five percent would register, and so on. After measurements on Earth, the entangled bursts of particles on their way to Mars would take on these ratios, instantly.
I believe it might be possible to build emitter-systems someday—even emitter systems with non-random polarization ratios. If not, then, as is sometimes said at NASA, Houston, we have a problem. FTL communication might not be possible.
On the other hand, if we can build these emitters, then we can know for sure that, upon measurement on Earth, the entangled photon-twins in the Mars-bound emitter-bursts will display the same statistical patterns; the same polarization ratios. And that means that anyone receiving bundles of entangled-photons from these encoded-emitters will be able to determine what they encode-for by the statistical distribution of their polarities.
Ok. Let’s assume we are able to build these emitter-systems and have set up our typewriter keyboard. How do we make sure when we press a key that the letter on the page is seen immediately by a distant observer? How do we configure the architectural geometry of the communication space?
This part is the most interesting, at least to me, because it’s success doesn’t depend on whether we send a single binary signal or a zoo of symbols—it’s the most critical. It does no one any good to instantly communicate polarization states to bunches of photons traveling at the speed of light to Mars. They still take three to twenty-two minutes to get there, even after we tell them instantly what state to be in or not. We want the machines on Mars to read our messages as we write them.
How can we do that? Maybe the method is becoming obvious to some readers. The answer is: we don’t measure the photons in our labs until their entangled twins have had time enough to travel to Mars (or wherever else they might be going). We entrap on Earth the photons from each “lettered” emitter and send their entangled twins to Mars. The photons from each “lettered” emitter here on Earth circulate in a holding bin (a kind of information-capacitor), until we need them to write our message.
As their entangled twins reach the Mars Rover (for example) we “type-out” our message by measuring the Earth-bound photons in the particular holding bins that encode the “letters” of our message; that is, we make the measurements that will expose the polarization-ratios of the “lettered” emissions we are using to “type” our message. Instantly, the entangled particle-bursts reaching Mars will take on these same polarization-ratios.
I can hear some folks saying, Wait a minute! Stop right there, Billy Lee! You can’t hold onto photons. You can’t store them. You can’t trap or retain them, because they are impervious to magnets and electrical fields. You can’t delay your measurements for five milliseconds, let alone five minutes or five days.
Well, to me that’s just a technical hurdle that clever people can jump over, if they set their minds to it. After all, it is possible to confine light for for short periods with simple barriers, like walls.
Muons are short-lived and would have to be accelerated to nearly light-speed to gain enough lifespan to be useful. They are 207 times heavier than electrons, but they travel well and penetrate obstacles easily. (Protons, by comparison, are nine times heavier than muons.) The National Security Agency (NSA) photographs every ship at sea with muon-penetrating technology to make sure none harbor nuclear weapons.
We also have a lot of experience with electrons. Electrons are long-lived—they don’t have to be accelerated to near light-speeds to be useful. Speed doesn’t matter, anyway.
Entangled particles don’t have to travel at light-speed to communicate well, nor do they have to live forever. All that is necessary is that the particles have time enough to get to Mars (or wherever they’re going) before we piggy-back onto their Earth-bound entangled partners to transmit our instant-messages.
Even if it takes days or weeks for our bursts of entangled-particles to travel to Mars, it makes no difference. We can run and accumulate a sufficiently robust loop of streaming emissions on Earth to enable us, soon enough, to “type” our messages in real time whenever we choose.
As long as we have control of and access to the emitted particle-twins on Earth, we can type out our messages (by measuring our captive Earth-bound twins at the appropriate time) to impose and transfer the statistical configuration of their rigged polarization ratios (or spins in the case of electrons or muons) to the Mars-arriving particle-bursts, creating a message which a detector on that planet can decode and deliver, instantly.
The challenge of instant-return messaging could be met by employing the same technologies on Mars (or wherever else) as on Earth. The trick at both ends of the communication pipe-line is to store (and if necessary replenish) all the elements of any possible communication in what can be thought of as streaming particle-emission capacitors.
Tracking and timing issues don’t require the development of new technologies; the engineering challenges are trivial by comparison and can be managed by dedicated computers. Discharging streaming information-capacitors to send ordered instant-messages in real-time is new—perhaps engineers can achieve instant long range communication through the magic of quantum entanglement.