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Quantum teleportation is real, but it's not what you think

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In 2017, physicists beamed photons from Tibet to a satellite passing more than 300 miles overhead. These particles jumping through space evoked wide-eyed sci-fi fantasies back on Earth: Could Star Trek transporters be far behind? Sorry for the buzzkill, but this real-world trick, called quantum teleportation, probably won’t ever send your body from one place to another. It’s essentially a super-secure data transfer, which is tough to do with the jumble of code that makes a human.



Photons and teensy bits of atoms are the most complex bodies we can send over long distances in a flash. Each particle of the same type—photon, neutron, ­electron—​is largely the same as every other member of its subatomic species.



Configurations known as quantum states distinguish them. Two photons spinning clockwise, for example, are identical. You can’t make one zip elsewhere with no lag time (sorry, that’s magic), but you can create its duplicate in another spot. Not so useful for moving people, but valuable for instantaneous, secure communication.



Let’s say I’m on Earth and want to share a secret with you, an astronaut. I create a scrambled code—one impossible to decipher without its key—and use it to email you an inscrutable missive. But how do I send the key without risk of a spy intercepting it?


I start by encoding it in binary using the states of a group of photons (I could say clockwise is 1, counter is 0). I can securely share the digits thanks to a trick that occurs when two particles of the same type interact: entanglement. If Photon 1 spins clockwise, Photon 2 whirls counter. If one changes, so does the other—no matter how far apart they are.



I can break up such a pair—one stays with me, one beams to you in a ray of light—and know their states will always be complementary. This means you can infer the info stored on my Earthly particle by measuring your own. All I have to do is wait for my half of the couple to take on the same state as a third photon—one that I encoded with a digit of binary—and tell you to examine your own. In an instant, it’s turned into a precious passkey.



Presto chango: You got the digit hidden on my secret particle without ever seeing it. Since the photon I beamed up to you didn’t actually contain the cipher until its entangled buddy switched to the right state, we never risked spilling our secrets to an interloper en route.



RELATED: In photos: a rare glimpse inside the heart of a quantum computer



Such transfers could become common in the next decade, but this process won’t translate well into human transport: One person contains around 1028 atoms. Copying all of that data would require breaking down the body to the atomic level (ouch!), which would almost certainly prove fatal. And then you’d have to perfectly reconstruct it from scratch out of particles waiting at the far end of the journey. And hey: Would that faxed version even be the same person as the original?


Perhaps it’s best to leave teleportation—and all of its philosophical implications—to ­science-fiction stories, and focus on finding less deadly modes of futuristic travel.



This article was originally published in the Spring 2019 Transportation issue of Popular Science.




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Written By Matthew R. Francis

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