On June 15th of this year, the Chinese satellite Micius beamed two photons, one each to research centers located about 1000 miles apart: one in the city of Delingha in northern China, and the other in the city of Lijiang in southern China. You may ask, so what?
According to Anton Zeilinger, a physicist at the University of Vienna, this was a very big deal. “This experiment is really important for the development of a future quantum internet,” he said. In fact, many researchers believe the Chinese have taken the lead in demonstrating a subatomic particle-based encryption technique that could ultimately transmit ultra-secure information to and from any locations on Earth.
And that’s because these two space-strewn photons weren’t just passengers on Micius, they were “quantum entangled”, meaning they could each be at two places at once, even 1000 miles apart. And they still communicate between themselves as if they were joined as one. If researchers in Delingha change their photon’s spin to “up”, the Lijiang photon’s spin will immediately change to “down”. Translate “up” to “1” and “down” to “0” and you can begin to see how this digital encoding would work.
Quantum Entanglement, what is that? Ah, that’s the singular question, and the answer has to do with the weird and seemingly-nonsensical-but-conclusively-substantiated world of quantum mechanics. And that in turn requires traveling down a rabbit hole, which I’ll just peek into here.
The science fiction-like physics (or maybe metaphysics) of quantum mechanics has both fascinated and frustrated me. I once took a college elective course called Elementary Quantum Mechanics, which may have been elementary to the professor (though now I doubt it), but it certainly wasn’t to me. I failed the final exam. After thirty minutes of puzzling how to solve fifteen quantum mechanics problems, I realized I hadn’t a clue and walked out.
I later learned that Richard Feynman, who won a Nobel Prize in Physics for the development of quantum electrodynamics, famously once wrote, “I think I can safely say that nobody understands quantum mechanics.” In fact, that opinion seems nearly unanimous among the giants in the field.
The underpinning of quantum mechanics demands that the reality of our universe is utterly at odds with any “common sense” idea about how things “should work”. And yet, this strange beast of physics has been challenged, tested and retested and verified by critics and supporters alike since the early 1900’s. In spite of its implausibility, it is the only technique that successfully addresses the problem of how all subatomic particles (that is, everything that our universe is made of) in fact behave, and it has never yet been found wanting.
And the problem is even bigger than that. There is no explanation of the behavior of real subatomic particles that allows for our understanding of reality to be correct. In other words, if everything we experience and comprehend about the “reality” that surrounds us is, in fact, the real thing, then these particles cannot behave the way they, in fact, do.
I’ll try to describe the kookiest property of subatomic particles, that feature called “quantum entanglement” (also referred to as “quantum teleportation” but don’t get excited, this only works for subatomic entities).
In simplest terms, once two subatomic particles make contact with one other, they remain indelibly one entity for as long as they both exist, no matter how far apart they later roam. They become intimately “entangled” with each other, so tightly interconnected and interwoven that a change in one of the particles immediately induces a complementary change in the other one.
And that change is immediate, even if the two particles are light years apart. If particle “a” changes it’s spin to “up”, its twin “b” changes its spin to “down” and there is no delay in the transmission of that information from “a” to “b”. It is literally instantaneous – not limited by the speed of light or any other known restriction.
In fact, it’s not clear that using a measurement of space-time like the speed of light is even relevant here. These entangled entities seem to exist in some dimension of immediacy that transcends the reality of the universe we know.
Never mind the billions of years it has taken faint light from some distant, aging galaxy to reach our telescopes. If an electron in that galaxy had ever made contact with an electron (maybe just after the Big Bang?) that has now, however unlikely, made its way to residence here on Earth, the two of them are still in instant continuous contact, still interacting like some otherworldly FaceTime buddies.
The deeper you delve into what that “really means” about the tiny and inscrutable scaffolding that holds literally everything in our universe together, the more you discover that it makes no logical sense. To quote Dr. Feynman again, ‘Do not keep saying to yourself, if you can possibly avoid it, ‘But how can it be like that?’ because you will get ‘down the drain’, into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.” That’s quantum entanglement and, however bizarre that seems, it really does work that way. And the Chinese are world leaders in taming it for cybersecurity.
If you’re in for venturing a bit into this alley, click on the links above. One of the best and most readable books I’ve encountered (thankfully written for people who don’t want the math) is Quantum Reality: Beyond the New Physics by Nick Herbert. Be warned, here be dragons.