Crewmembers aboard the starship Enterprise on the iconic TV series "Star Trek" could "beam up" from planets to starships, making travel between great distances look easy. While these capabilities are clearly fictional, researchers have now performed "quantum teleportation" of laser pulses over several miles within two city networks of fiber optics.
Although the method described in the research will not replace city subways or buses with transporter booths, it could help lead to hack-proof telecommunications networks, as well as a "quantum internet" to help extraordinarily powerful quantum computers talk to one another.
Teleporting an object from one point in the universe to another without it moving through the space in between may sound like science fiction, but quantum physicists have actually been experimenting with quantum teleportation since 1998. The current distance record for quantum teleportation — a feat announced in 2012 — is about 89 miles (143 kilometers), between the two Canary Islands of La Palma and Tenerife, off the northwest coast of Africa. [10 Futuristic Technologies 'Star Trek' Fans Would Love to See]
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Spooky action
Quantum teleportation relies on the bizarre nature of quantum physics, which finds that the fundamental building blocks of the universe, such as subatomic particles, can essentially exist in two or more places at once. Specifically, quantum teleportation depends on a strange phenomenon known as "quantum entanglement," in which objects can become linked and influence each other instantaneously, no matter how far apart they are.
Currently, researchers cannot teleport matter (say, a human) across space, but they can use quantum teleportation to beam information from one place to another. The quantum teleportation of an electron, for example, would first involve entangling a pair of electrons. Next, one of the two electrons — the one to be teleported — would stay in one place while the other electron would be physically transported to whatever destination is desired.
Then, the fundamental details or "quantum state" of the electron to be teleported are analyzed — an act that also destroys its quantum state. Finally, that data is sent to the destination, where it can be used on the other electron to recreate the first one, so that it is indistinguishable from the original. For all intents and purposes, that electron has teleported. (Because the data is sent using regular signals such as light pulses or electrons, quantum teleportation can proceed no faster than the speed of light.)
Now, two research groups independently report quantum teleportation over several miles of fiber-optic networks in the cities of Hefei, China, and Calgary, Alberta. The scientists detailed their findings online Sept. 19 in two independent papers in the journal Nature Photonics.
Futuristic tech
Quantum teleportation is the key to many potential future technologies. For instance, quantum cryptography could use quantum teleportation to transmit data securely between two points in a way that can automatically detect any intrusion. In addition, people could use quantum teleportation in a "quantum internet" to share data with quantum computers, which previous research suggested could run more calculations in an instant than there are atoms in the universe. [8 Ways You Can See Einstein's Theory of Relativity in Real Life]
"In the future, if you have a quantum computer, if users wanted to use it, they could send data to the quantum computer and get results, just like with modern cloud computation," Qiang Zhang, a quantum engineer at the University of Science and Technology of China and co-senior author of the Hefei work, told Live Science.
Each of the two quantum-teleportation experiments involved communication across up to 7.7 miles (12.5 km) between three d istinct locations to mimic the structure of future quantum networks. The only previous experiment with such a three-lab setup involved distances of less than 0.6 miles (1 km).
Previous experiments involving a three-lab setup used pulses of visible light, which cannot travel great distances within optical fibers. In contrast, the new studies employed the kind of infrared light often used in everyday telecommunications networks, which can travel farther. They also used pre-existing fiber-optic networks in each city.
Long-distance quantum teleportation involves laser beams that are synchronized until they are indistinguishable from each other down to the level of single photons, even after zipping through several miles of fiber optics laid within changing environments. Both research teams benefited from recent improvements in single-photon detectors made by the telecommunications industry,the researchers said.
"We are proud that the results observed in field tests have not degraded compared with those observed in laboratory tests," Qi-Chao Sun, a quantum engineer at the University of Science and Technology of China and lead author of the Hefei study, told Live Science. "This means that our system is robust against noises arising from complex environments in the real world."
The Calgary experiment had a faster teleportation rate of about 17 photons per minute (or 1,020 per hour), compared to about two photons per hour for the Hefei experiment. However, the procedures the Calgary researchers carried out to accomplish these teleportation speeds limit its immediate practical applications, Frédéric Grosshans, a quantum information researcher at the University of Paris-Sud in France, said in a review of both teams' studies.
Both research teams also used a variety of methods to keep lasers synchronized with one another. Each group used a different technique, which suggests that elements from both strategies could be combined for even better results, Grosshans wrote in his review.
One future direction will be to extend quantum teleportation networks "to 100-kilometer [60 miles] scales, which will allow intercity quantum teleportation," Sun said. This will involve improving detector efficiency and suppressing sources of interference, Sun added.
LiveScience, 2016-09-23,
