Shanghai scientists set space teleportation record
A packet of quantum information was successfully beamed from Tibet to a satellite in high orbitBy DAVE MAKICHUKSEPTEMBER 4, 2021Print
It first hit our television sets on Sept. 8, 1966.
The television show was called Star Trek, and, it featured a bold group of space travellers aboard the starship Enterprise.
It was then that we were formally introduced to teleportation — a cool concept that allowed the ship to beam people and things to any coordinate.https://beab4626136a6279c494d9194afbd3d3.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html?n=0
Many technologies featured in the sci-fi TV series have actually come true today, including teleportation.
Alas, we’re not talking about “Beam me up, Scotty.” Nobody has beamed anyone up to a spaceship.
Rather, they have sent a packet of quantum information from Tibet to the Micius satellite in orbit, up to 870 miles (1,400 kilometers) above the Earth’s surface — a record for teleportation.
More specifically, the Chinese team, led by Ji-Gang Ren at the University of Science and Technology in Shanghai, beamed the quantum state of a photon (information about how it is polarized) into orbit, Space.com reported.
Not only did the team set a record for quantum teleportation distance, they also showed that one can build a practical system for long-distance quantum communications.https://beab4626136a6279c494d9194afbd3d3.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html?n=0
Such a communication system would be impossible to eavesdrop on without alerting the users, which would make online communications much more secure.
Experiments like this have been done before, but Howard Wiseman, director of the Center for Quantum Dynamics at Griffith University in Brisbane, Australia, told Space.com in an email that this one expands the possibilities for the technology.
“This is much more difficult, because it is to a rapidly moving target, and you have your quantum detectors way out in space where they have to work without anyone fiddling with them,” he said. “It is a big step towards global-scale quantum communication.”
The experiment takes advantage of one of several phenomena that describes quantum mechanics: entanglement, or “spooky action at a distance,” as Albert Einstein called it.
When two particles are entangled, they remain connected so that an action performed on one affects the other as well, no matter how far apart the two are.
In the same vein, when one measures the state of one particle in the entangled duo, you’d automatically know the state of the second.
Physicists call the states “correlated,” because if one particle — a photon, for example — is in an “up” state, its entangled partner will be in a “down” state — a kind of mirror image. (Strictly speaking, there are four possible combinations for the two particles to be in).
The weird part is that once the state of the first particle is measured, the second one somehow “knows” what state it should be in. The information seems to travel instantaneously.
But while it sounds like information is traveling faster than light, there’s no way to use this property as an instantaneous messaging system.
That’s because even though the states of entangled particles are correlated, you can’t know what they are before you measure them, nor can you control the state.https://beab4626136a6279c494d9194afbd3d3.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html?n=0
What entangled particles can do is act as perfect authenticators for messages. The reason is that the act of observing a particle changes its behavior.
To simplify things, think about it this way:
It’s like having the only two copies of a book. Alice and Bob each get one copy. (They’re always named Alice and Bob in quantum physics.)
Alice opens her copy of the book and she can see the table of contents. If she then sends a message to Bob and tells him what the table of contents is, he can then read the book.
If Bob opens the book without Alice telling him about the index, it will be garbled. He needs this index to make sense of the information.
Since they’re the only two people in the world with copies of the book, when Bob does read the information, he can be sure that nobody else has it.
But how does Alice send the table of contents to Bob? By any means she likes. Email. Fax. Carrier pigeon. The second communication channel here is bound by all the standard laws of physics.
So why beam it into space?
If these same photons were sent over fiber-optic cables, rather than through space, the connection between the photons would be destroyed by interference from factors such as heat and vibration, or even random interactions with the cable.
A satellite, on the other hand, is outside of the atmosphere, and there’s much less chance of the entangled photon getting spoiled.
“With fiber you lose many of the photons,” said Bill Munro, a senior research scientist at NTT’s basic research laboratory, in an interview with Space.com.
Beaming photons to orbit means that you could build an actual communications system.
“You could beam from China to Washington or New York.” The problem of reducing the interference with the signals and getting more photons through, Munro said, is a technical and engineering problem that can be solved.
Both Munro and Wiseman noted that often people think of teleportation as moving an actual object (or a photon) form one place to another.
“People have this ‘Star Trek’ approach,” Munro said. “They think of atoms being teleported.
“What we’re moving is information from one [quantum] bit to another [quantum] bit. There’s not matter — only information. That’s hard to get your head around.”
The study appeared in the ArXiv on July 4.