An international team of physicists has broken the distance record for "quantum teleportation" with the instantaneous transmission of quantum states encoded in photons over the 143 kilometers (89 miles) separating facilities on the islands of La Palma and Tenerife in the Canary Islands.
"Our experiment shows how mature 'quantum technologies' are today, and how useful they can be for practical applications," said team leader Anton Zeilinger in a statement. "The next step is satellite-based quantum teleportation, which should enable quantum communication on a global scale."
Quantum teleportation has been heralded as having enormous potential for sending un-hackable messages between quantum computers on a future quantum Internet. It uses the peculiarities of entangled quantum states in a pair of particles like photons to get around the limitations of the universe's "speed limit," the speed of light. If you change the quantum state of one entangled photon, it turns out, that change is instantly reflected in the other photon regardless of its physical distance from the transmitting, entangled particle.
What that means is that you could potentially send a message across the Solar System (or even the galaxy or the universe itself) and have it instantly appear in front of your recipient's eyes. Transmitting such a message by radio from Earth to Mars, for example, takes between three and 20 minutes to arrive, depending on the two planets' proximity at the time.
But there's a catch—at present, quantum teleportation isn't actually instantaneous for practical purposes. To start with, the Canary Island experiment didn't actually happen very recently. According to Alex Knapp of Forbes, the team pulled off its quantum teleportation feat last May but is only now publishing its findings in this week's issue of Nature.
That's just a housekeeping note, of course. The reasons for why practical applications of quantum teleportation take a bit more time than advertised are more complex.
First you have to get an entangled receiver photon out to where you want it to start receiving quantum teleported messages from the entangled transmitter photon that stays back at home. That outward trip is still restricted by the speed of light, meaning it's still going to take you several minutes at best to set up communication with Mars (or in the case of the Canary Islands experiment, the non-instantaneous amount of time it took to send the entangled receiver photon from one island to the other).
But you'd also need a physical facility on the Red Planet capable of housing your receiver photon safely. That would presumably have to be built on Earth and then shipped over several months to our neighboring planet via spacecraft.
Furthermore, it turns out that transporting an entangled photon over a distance without messing things up is an incredibly delicate task, which makes the accomplishment of the Canary Islands team remarkable even if the distance traveled seems pretty short.
"The realization of quantum teleportation over a distance of 143 kilometers has been a huge technological challenge," said team member Xiao-song Ma. The task involved several innovative new techniques developed to transmit an entangled photon wirelessly across "the turbulent atmosphere between the two islands" because using fiber optic cables was not a suitable option, the scientist added.
The gap between La Palma and Tenerife isn't tremendous, but the successful quantum teleportation experiment by physicists associated with the University of Vienna and the Austrian Academy of Sciences beat the previous record set by a Chinese research team by 46 kilometers. That doesn't mean the two quantum teleportation projects are at odds, according to Zeilinger, who is now aiming his sights on near-Earth orbit if not the stars.
"We have now taken a major step in this direction and will use our know-how in an international cooperation, which involves our colleagues at the Chinese Academy of Sciences. The goal is to launch a 'quantum satellite mission,'" he said.