I have a confession to make. For years I’ve watched series and movies in the Star Trek and Star Wars franchises, thrilled at the near-instantaneous space travel between distant star systems. Warp speed and hyper drive are both examples of superluminal speed – speed faster than the speed of light. It’s made possible by prying open wormholes posited to exist at sub-atomic scales.
However, I had to set credulity aside to enjoy the story lines as they unfolded. Why? Because the amount of energy required to open up a wormhole large enough for a space craft to fly into it would literally require the energy equivalent of the output of a star. With all due respect to the miracles of fusion power and matter-antimatter annihilation harnessed on these sci-fi franchises, the energy released would vaporize any spaceship long before opening the wormhole. Based on our current understanding of quantum physics, it just ain’t gonna happen.
But there’s another miracle occurring in these sci-fi franchises most of us completely overlook – superluminal communication across whole parsecs of space. Information miraculously exceeds the speed of light, violating the principal of locality in Einstein’s theory of relativity. It’s utterly impossible. Or is it?
In the realm of quantum communication, scientists experiment with a state of matter known as quantum entanglement. Recently, scientists have been creating pairs of entangled photons, electrons, even solid-state qubits. It’s possible to entangle whole tranches of matter. The super-cooled Bose-Einstein condensates are an example.
Polarization is one of many quantum states that can be entangled. Let’s assume we measure the polarity of a pair of entangled photons together and get a polarity of 0. If we were to measure or observe the polarization of the individual photons one would measure 1, and the other -1(I am simplifying this particular example). Furthermore, if we were to repeat this experiment, whatever polarity we measured for the first photon, measuring the second photon would always yield the opposite polarity. Always. Once measured, the entangled photons decohere(the entanglement wave function collapses, using quantum mechanics jargon), meaning they return to their previous independent random quantum state statuses
Now let’s separate these entangled photons, measuring one across the room from the other. If you measure the first and get a result of 1, then I measure the second, I will always get a result of -1. Always. The behavior of one entangled particle, once measured, always influences the state of the other. Experiments show that this influence of one entangled particle’s quantum state on the other when measured occurs instantaneously, no matter how far apart the entangled particles are. This phenomenon is what Albert Einstein famously described as “spooky action at a distance”. Entanglement underpins the theory of quantum mechanics – and experimental observations made since Einstein’s pronouncement verify it.
Moving a unit of an entangled pair (or in the case of a photon, to allow it to travel) across a distance while maintaining its entanglement is called quantum teleportation. It’s the basis for the developing field of quantum communication. If a string of entangled photons were sent to a distant receiver, that receiver read the quantum states of the received photons, then sent the results back to the sender, who compared it to the states of their half of the entangled pairs, the sum should total 0 (in our simplified example). Any other sum indicates that someone intercepted the photons and measured (i.e. read) them, causing their entanglement wave function to collapse. The legitimate receiver would observe and return to the sender randomly decohered measurements that would not pair properly with the expected results. This ability to detect an eavesdropper is the basis for quantum encryption keys. Upon learning of the intercept, a new key would be generated and sent - the process repeated until the key was not intercepted – allowing the encrypted message to be sent. A quantum encrypted message is absolutely secure using an entangled quantum key.
In 2017, a Chinese science team headed by Jian-Wei Pan set the record for quantum teleportation between an orbiting satellite and a ground base in Tibet, 1,700km. There seems to be no limit to the distance that entangled pairs can maintain their quantum interaction, provided they don’t interact with their environment first and decohere. Which brings me back to the topic of superluminal communication.
Can the phenomenon of quantum teleportation – the separation of entangled matter – be exploited to somehow send messages superluminally? Current interpretation of quantum mechanics says “no”, but the theory of quantum mechanics is still incomplete. There is no “quantum gravity” as of yet. And the phenomenon of entanglement has yet to be fully explored and described.
Perhaps some day we’ll figure out how to reset entanglement after a measurement has been taken, allowing one party to “measure” the quantum states created by the other party, comparing the results to a catalog of quantum states that correspond to letters of the alphabet, for example.
When will we know whether or not this is possible? Probably not in my lifetime. But it sure makes for interesting fiction. So, with apologies to the quantum physicists in my reading audience, look for the employment of this yet undiscovered phenomenon in my upcoming book, Red Dragon.
Happy reading and...
Happy Holidays!
For further reading
https://quantumxc.com/blog/is-quantum-communication-faster-than-the-speed-of-light/https://www.science.org/content/article/china-s-quantum-satellite-achieves-spooky-action-record-distancehttps://en.wikipedia.org/wiki/Quantum_entanglement
