Ansibles, Hyperwaves, and Wormholes: The search for FTL communication Kiowa Wells Introduction I’ve been a science-fiction nerd for as long as I can remember. As such, the idea of faster-thanlight communication was not only formative for me, but also taken for granted. After all, how can a galaxy-spanning civilization function if messages have to travel at light speed? How could we ever hope to communicate meaningfully with distant civilizations? As humans continue to venture further out into space, this question begins to take on more significance. Unfortunately, while FTL communication is no less nebulous and pluriform from a physics standpoint than it is in sci-fi, it is anything but a given. There are nevertheless some theories out there, grasping though they may be, that offer a glimmer of hope that it’s more than just a pipe dream. Quantum Mechanics Quantum entanglement is the subject of much speculation and misunderstanding. It is frequently touted as a potential inroad to FTL communication, an idea which has been heartily refuted by most of the physics community for some time. The main reason behind this line of thinking stems from an aspect of the Copenhagen interpretation of quantum mechanics called quantum superposition. This is the idea that a particle isn’t in any predetermined state at a given time, but is instead in every state until it is observed or interacts somehow with the classical environment to the extent that it decoheres. At the moment of observation, the particle is said to collapse into one of its possible states. This naturally gives rise to a violation of relativity known as the EPR Paradox (named for some famous guys [1]), which I have tried to sum up as briefly as possible as follows: Conservation of angular momentum dictates that if a quantum system emits some number of particles that have spin (i.e. bosons or fermions), they must be correlated in such a way that their spins cancel. For a simple case of two particles, A and B, this implies that the spin of particle A must be opposite that of particle B when they collapse. In other words, to know one’s state is to know the other’s. Such a pair are said to be entangled. This holds for multi-particle systems as well, although the correlations can obviously be more complex than in the case above. Applying the Copenhagen interpretation to this, we find that when we observe a particle to be in a particular state, its partner must somehow instantaneously assume a correlated state regardless of the distance that separates the pair. This means that in the case where an entangled pair is separated by a significant distance, there would have to be some form of instantaneous (read FTL) communication of information between the particles to account for their simultaneous collapse. That is the paradox in a nutshell (I think). The crazy thing is that experiment has consistently borne out the momentum-conserving correlation, which means the Copenhagen interpretation must violate relativity. That sounds pretty good for FTL communication. If quantum superposition is how reality actually functions, we should be able to turn it to our advantage, right? Suppose for example that two experimenters, Ashurbanipal and Bhagyanandana, say, each have 10,000 complementary entangled “partner” particles. Ashurbanipal is on Mars and Bhagyanandana is at a lab in Bengaluru. Could Ashurbanipal not send binary coded messages instantaneously by inducing a series of desired states in each particle? Not according to quantum theorists. The prevailing line of thinking is that the collapse that happens on the point of measurement is random: Sadly, we have no way of inducing a particle to collapse into a state of our choosing. Furthermore, if we were to figure out how to manipulate the state of the particle on Mars, it might simply change the whole entangled state to include whatever apparatus we used to do so, with unpredictable consequences regarding the particle on earth. For the time being, at least where Copenhagen interpretation is concerned, coded messages are off the table. Bohmian Mechanics The de Broglie-Bohm interpretation considers waves and particles to be discrete, real entities, rejecting the notion of wave-particles in superposition. This conveniently eliminates the notorious measurement problem of quantum mechanics in that a particle with a position and trajectory is not collapsed into some spin state by the act of measuring. Instead, the position and velocity of the particle depend on hidden variables belonging to a wave of ‘quantum potential’ which permeates the universe, informing the position of particles as they move through space. [2,3] Importantly, this interpretation is not subject to the no-communication theorem because the variables are non-local properties of a wavefunction extending throughout space. In this way, Bohm’s interpretation is not only deterministic, but also violates relativity. The position and velocity of a given particle in a system depends on all of the other particles in that system (see the guiding equation, derived below). In effect, this suggests that all of the particles are ‘transmitting’ information between each other, and doing so instantaneously. Despite the obvious deterministic overtones of such a system, the theory still allows for uncertainty, only it isn’t probabilistic; rather, it is a function of our inability to determine a given particle’s initial conditions. What’s incredible is that this interpretation consistently bears out experimental evidence just as faithfully as “traditional” quantum mechanics, including the infamous doubleslit experiment. In fact, there have recently been classical experiments using oil droplets and sound waves which manage to demonstrate just such wave-particle interactions in real time, which are absolutely worth checking out. [4,5] Ironically, John Bell, who is frequently credited with proving quantum mechanics, was to the contrary a staunch proponent of the de Broglie Bohm interpretation, and one of very few at that. This is summed up so eloquently in this wellknown quote by Bell himself (in reference to the double-slit experiment) that I couldn’t resist reproducing it here: While the founding fathers agonized over the question "particle" or "wave," de Broglie in 1925 proposed the obvious answer "particle" and "wave." Is it not clear from the smallness of the scintillations on the screen that we have to do with a particle? And is it not clear, from the diffraction and interference patterns, that the motion of the particle is directed by a wave ? De Broglie showed in detail how the motion of a particle, passing through just one of two holes in a screen, could be influenced by waves propagating through both holes. And so influenced that the particle does not go where the waves cancel out, but is attracted to where they cooperate. This idea seems to me so natural and simple, to resolve the wave-Particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored. [6] There are two main equations that define Bohmian Mechanics, namely the Hamiltonian and the guiding equation, which is a modification of Schrodinger’s equation to account for the effects of the quantum force. As usual, the Hamiltonian is given by Ģ š = (šā š» š )š . šš” (1) Since the guiding equation models some particle Q’s evolving position, it can be derived with the help of de Broglie’s hypothesis as follows: p = mv = āk ā¶ v = āk šQ š = m šš” (2) and š = š“š š(kš„−šš”) ā¶ ∇š = š“ššš š(kš„−šš”) = škš ā¶ k = ∇š ∇š = Im šš š . (3) Finally, substituting for k in Eq. 2 gives the guiding equation: šQ š ā ∇š (Q1 , … Q š ) = Im šš” m š (4) [2,7] All of this suggests that it should be possible to exploit this wave of quantum potential to use entangled particles for faster than light communication: If one of a pair of entangled particles is disrupted, the “communication” of this information would not need to occur via a signal, but through the particles’ interactions with the guiding wave. Enter the quantum equilibrium hypothesis (which is basically just the Born rule), which states that the positional probability distribution for a particle at time t is equal to the absolute value of the wavefunction squared, or ρ = |ψ2|. This means that a series of systems that share a wavefunction and have evolved into a state of quantum equilibrium according to Schrödinger’s equation are generally well behaved, which is basically a fancy way of saying that our observable universe has settled into a relatively high state of entropy from some unknown initial conditions. What makes quantum equilibrium a hypothesis and not a rule is that Bohmian mechanics allows for conditions of quantum nonequilibrium, under which it is possible that ρ ≠ |ψ2|, and QM, relativity, and probably a bunch of other principles are out the window. Importantly, if Bohmian Mechanics holds, a system of entangled particles in these circumstances could indeed be used for FTL communication. There has been some interesting hypothesizing about the existence and exploitation of non-equilibrium artifacts [8], but that rabbit hole is beyond the scope of this paper. We established earlier that from the Bohmian perspective, if particles in an entangled system do “communicate” faster than light, they do so via some real wave of ‘quantum potential’. It’s common when talking about FTL communication to use the term “instantaneous,” but we should be careful here: If physical effects are indeed transmitted amongst all of the particles in the system via wave, there should be some way to model the corresponding interval using wave mechanics. Because it can be thought of as a standing wave, each particle’s interaction with it should result in some phase change, however minor, which would then propagate throughout the rest of the wave. Propagation of this nature need not be thought of as instantaneous; to the contrary, it may be more useful to imagine it as still requiring some interval, just an incredibly small one. (This has the added benefit of doing away with the magical undertones that plague this line of inquiry). Depending on what the medium of this so-called quantum potential is (subspace? neutrinos? some form of energy?), is there any good reason why such a phase shift could not propagate faster than light? If we could find some way to model this, could we amend the guiding equation to account for infinitesimal delay? By what methods could we undertake to identify what the quantum potential is?! There are probably already good answers for at least some of these questions, but time constraints demand we conclude this section here, however prematurely. Wormholes At last we arrive at the FTL cheat code: Wormholes! [9] Imagine a system where entangled particles never need leave each other’s side, yet a route is established via classical transportation which connects them to distant points in space. What about supermassive blackholes? If two black holes converge that are massive enough to cause a wormhole, how could anything moving through it ever hope to escape the event horizon? Don’t even worry about it: Exotic matter!!!!! Yes, wormholes have it all. If we ever figure out how to create or take advantage of wormholes, life will be way more interesting. Here’s hoping! Editor’s note: The author wishes to communicate that he really does hope that wormholes exist, and that he gets the chance to study them in the future. Sadly, he ran out of time and had no other choice than to give them the above treatment. Conclusion There are few better ways to alienate yourself in a room full of physicists than to string the words “entanglement” and “faster than light communication” together in a sentence. I put forth that while this reaction is understandable, most of those same physicists will also tell you with a straight face how wave-particles are neither one or the other or in any one state until we look at them, at which point they pick one at random and tell their friends about it instantaneously. It is my sincere hope that we can one day move beyond the Copenhagen interpretation and focus instead on turning science fiction into reality. References [1] A. Einstein, B. Podolsky, and N. Rosen, "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete ?," Physical Review, vol. 47, pp. 777-780, May 1935. [2] Sheldon Goldstein, ""Bohmian Mechanics"," The Stanford Encyclopedia of Philosophy, Fall 2021. [Online]. https://plato.stanford.edu/entries/qm-bohm/ [3] Glass Universe Looking. (2017, August) Do we have to accept Quantum weirdness? De Broglie Bohm Pilot Wave Theory explained. YouTube. [Online]. https://www.youtube.com/watch?v=r0plv_nIzsQ [4] Veritasium. (2016, November) Is This What Quantum Mechanics Looks Like? YouTube. [Online]. https://www.youtube.com/watch?v=WIyTZDHuarQ [5] Suzie Protiere, Arezki Boudaoud, and Yves Couder, "Particle–wave association on a fluid interface," J. Fluid Mech., vol. 554, pp. 85-108, 2006. [Online]. https://julientaylor.com/DUALWALKERS/PDF/2006,%20particlewave%20JFM.pdf [6] J.S. Bell, "Six Possible Worlds of Quantum Mechanics," Foundations of Physics, vol. 22, no. 10, 1992. [Online]. https://personal.lse.ac.uk/robert49/teaching/partiii/pdf/BellSixPossibleWorldsQmMechsFdnsPhysics1992.pdf [7] Wikipedia contributors. (2023) Quantum non-equilibrium, Wikipedia. [Online]. https://en.wikipedia.org/w/index.php?title=Quantum_non-equilibrium&oldid=1187477000 [8] Antony Valentini, "Subquantum Information and Computation," Pramana - J Phys, vol. 59, pp. 269-277, 2002. [Online]. https://arxiv.org/pdf/quant-ph/0203049 [9] Nick Sparks, "Wormholes".
