AIR & SPACE MAGAZINE

No, Quantum Teleportation Won’t Let Us Send Instant Messages to Alpha Centauri

Quantum computers may have other benefits for space exploration, however.

August 10, 2017

In what sounds like a “Beam me up, Scotty” moment, Chinese scientists recently teleported the first photons to orbit. But unlike the glowing transporter in Star Trek, teleportation experiments in 2017 still have to follow the laws of physics, which means that instant travel to—or even communication with—nearby stars won’t happen.

The Chinese experiment began last year, when a satellite called Micius (named after an ancient Chinese philosopher) blasted off on top of a Long March rocket. Equipped with a photon receiver, Micius passes over ground stations at the same time every day, during which times scientists can beam up a stream of photons.

“Beaming,” in this case, doesn’t mean the instantaneous transfer of photons from one location to another. Like anything else, these elementary particles can travel no faster than the speed of light. Their ability to carry information relies on a principle called quantum entanglement, which happens when tiny particles (including photons) form at the same time and place. In the weird world of quantum physics, this means the two objects share the same existence (or more technically, have the same wave function).

Even stranger, this shared existence continues even if you separate the photons by centimeters, meters, or kilometers. If you measure one photon, it will affect the state of the other, entangled photon. This principle has been demonstrated several times in labs, over fiber optic cables, and even on airplanes, but never in a space experiment.

The Micius team says their ground-to-space entanglement took place over 500 kilometers, shattering the previous entanglement record (100 kilometers) five-fold. Because atmospheric interference could break the entanglement, the Chinese researchers beamed the entangled photons from a ground station in Tibet located more than 4,000 meters above sea level. The results weren’t perfect, though; only 911 photons got through to space, out of millions of photons sent.

“This is remarkable on many levels: a 500 km distance, the challenges of stabilizing and tracking the satellite, and atmospheric turbulence,” said Shellee Dyer, a member of the faint photonics group at the U.S. National Institute of Standards and Technology, in an e-mail. “I am not aware of any specific U.S. research that focuses specifically on ground-to-satellite quantum teleportation, [although] there have been experiments demonstrating quantum teleportation and pushing the limits of distance.”

Does the research have any application to space travel?

The privately funded Breakthrough Initiative proposes to send a flotilla of tiny spacecraft to Alpha Centauri around 2038, at 15 to 20 percent of the speed of light. Brian Koberlein, an astrophysicist at the Rochester Institute of Technology in New York, points out that even if the nanosatellites carried entangled particles on board, we wouldn’t be able to communicate with the spacecraft instantaneously.

“You have to send a beam of light to the satellite to entangle with the other one [on the ground],” he says. That beam would be limited to the speed of light, and “only when you do the measurement [does] the state change instantaneously. You could not decide to send a message now, and get it to Alpha Centauri in less than four years.”

While we can’t use quantum teleportation to shorten interstellar distances, future quantum computers will almost certainly be used to help solve critical problems related to space travel. NASA is among the many agencies and private companies playing in this technology sector, which has application in fields ranging from aeronautical simulation to computer security and cryptography. We may see the first practical quantum computers coming online within the next few years.