IN 20 17, PHYSICISTS BEAMED PHOTONS
from Tibet to a satellite passing more than
300 miles overhead. These particles jump-
ing 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 at-
oms 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 quan-
tum 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 in-
scrutable missive. But how do I send the key
without risk of a spy intercepting it?DEEPER CUT
a commute so quick,
you could just die
I start by encoding it in binary using the
states of a group of photons (I could say clock-
wise 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: entangle-
ment. 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 complemen-
tary. 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.
Such transfers could become common in
the next decade, but this process won’t trans-
late 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.by Matthew R. Francis / illustration by Cristiana Couceiro SPRING 2019 • POPSCI.COM 19