Physics

Chinese satellite shatters quantum teleportation distance record

The Chiense satellite Micius has helped break the quantum teleportation distance record, transmitting entangled photons across a distance of 1,200 km (746 mi)
The Chiense satellite Micius has helped break the quantum teleportation distance record, transmitting entangled photons across a distance of 1,200 km (746 mi)
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The Chiense satellite Micius has helped break the quantum teleportation distance record, transmitting entangled photons across a distance of 1,200 km (746 mi)
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The Chiense satellite Micius has helped break the quantum teleportation distance record, transmitting entangled photons across a distance of 1,200 km (746 mi)

Chinese scientists have smashed the quantum entanglement distance record. Transmitting information through entangled photons had previously only been possible up to about 100 km (62 mi), but using the Micius satellite launched in August, information has effectively been teleported as far as 1,200 km (746 mi).

Quantum entanglement is a phenomenon so bizarre that even Einstein argued against its existence, famously referring to it as "spooky action at a distance." Pairs of particles can be inextricably linked, so that the state of one can be inferred from the other, no matter how far apart they may be. Essentially, this process can be used to instantly "teleport" information between them over theoretically infinite distances, which was Einstein's issue with the idea: it violated the law of general relativity that says nothing can travel faster than the speed of light.

As useful as it might someday be, quantum effects are very sensitive to interference from the environment. Previous experiments encased the photons in an optical fiber to protect them, passing the message down the line from particle to particle. This method was used to set the previous record of 100 km, but the longer the distance, the higher the chance that the message will be lost or distorted.

Launched by the Quantum Experiments at Space Scale (QUESS) program, the Micius satellite was the first step towards building a global quantum communication network. Instead of physical fibers, the system sends entangled photons via laser beams, and although that can help minimize interference, lining up the source and the receiver brings its own challenges – especially when the satellite is moving so fast.

"It will be like tossing a coin from a plane at 100,000 meters above the sea level exactly into the slot of a rotating piggy bank," Wang Jianyu, the QUESS project's chief commander, said in a statement last August, when the satellite was first launched.

But the team has now managed to pull off that seemingly impossible feat, using the system to transmit quantum-entangled photons over a distance of 1,200 km. To do so, the laser beam on the satellite passes through a beam splitter, which creates two different polarized states: one for receiving entangled photons and one for sending them. Using this, Micius communicates with three different receiving satellites, over a distance 12 times larger than the previous record, and far more efficiently than optical fibers are capable of.

"For quantum networking, in this work, we have already achieved a two-photon entanglement distribution efficiency a trillion times more efficient than using the best telecommunication fibers," says Jian-Wei Pan, lead researcher on the project.

A quantum communication network could not only make telecommunications much faster, but more secure: the sensitivity of entangled photons to interference actually works to their advantage. If an unauthorized third party tries to tap into a signal, they'll interrupt it, rendering it unreadable to them and alerting the official users to the presence of the hack.

The results were published in the journal Science.

Source: American Association for the Advancement of Science

14 comments
Martin Winlow
I don't want to knock Mr Einstein (and perhaps someone who knows more about quantum physics than me can help me out here) but, surely, 2 photons of light, emitted from opposite sides of the Sun, will have a speed *relative to each other* of twice the speed of light...? So, 'poof' goes that theory...No?
Mike Emery
IT IS ALL ENTANGLED EVEN SOUND CAN GO FASTER THAN LIGHT http://blog.hasslberger.com/docs/THE_TIME_CONTINUM-3.pdf
piperTom
Previous commenter would be right (about two photons) IF time and space were Euclidean. It was Einstein greatest intuitive leap to consider that might not be true. Space-time is not Euclidean and you cannot simply add two velocities together. Besides that, it's not quite what Einstein said -- "nothing can go faster than light" is a simplification. Easy example: take your laser pointer and wave it at the moon. The (weak!) spot of light on the moon's surface easily exceeds the speed of light .Better to say "nothing can deliver information or energy faster than light would".
Vernon Miles Kerr
It seems the effects of quantum entanglement do not violate relativity if one pictures the entangled photons as at opposite ends of a 1200 kilometer piece of twine. Pulling on one end of the twine would immediately be felt at the other end, regardless of distance. Travel time: zero.
RaoulMarais
@Martin I don't pretend to be much knowledgeable about this either but here are 2 links that describe why the relative velocity of any 2 entities (photons) can only be at most c = speed of light. In essence the bottom line is that Vrelative = V1 - V2 is only approximately correct when neither of the velocities are close to c. There is thus a different formula that describes how relative velocity functions in the special relativity model. http://www.physicscentral.com/experiment/askaphysicist/physics-answer.cfm?uid=20130130105151 https://www.quora.com/If-the-relative-velocity-of-two-particles-moving-with-speed-of-light-opposite-to-each-other-is-calculated-will-it-be-2c And another bonus link on the idea/importance of the speed of light. https://www.livescience.com/16248-speed-light-special-relativity-neutrinos.html
JimFox
Classical physics finds that mass increases with speed, becoming infinite at lightspeed; which means only massless items can travel at lightspeed? Photons are massless and can have the properties of both particle and wave. As for quantum mechanics, it is incomprehensible to me- Feynman - Nobody understands Quantum Mechanics- https://www.youtube.com/watch?v=w3ZRLllWgHI
ezeflyer
Vernon Miles Kerr gave the best explanation of quantum entanglement I've ever seen.
Douglas Bennett Rogers
The transit time could easily be measured in this experiment. One would think that it would just be part of the data. You could see right away if it was faster than light. Two photons emitted in opposite directions from a source will be seen to separate at 2c. The separation speed as seen from either photon is infinite.
CharlieSeattle
Beam me up, Scotty...............in one piece please!
Stephen N Russell
To Upscale for human use??? later IE say 2050??
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