A Quantum Record
Not long ago, in the early 1990s, scientists only speculated that teleportation using quantum physics could be possible. Since then, the process has become a standard operation in quantum optics labs around the world. In fact, just last year, two separate teams conducted the world's first quantum teleportation outside of a laboratory.
Now, researchers in China have taken the process a few steps further: they successfully teleported a photon from Earth to a satellite orbiting more than 500 km (311 mi) away.
The satellite, called Micius, is a highly sensitive photo receiver capable of detecting the quantum states of single photons fired from the ground. Micius was launched to allow scientists to test various technological building blocks for quantum feats including entanglement, cryptography, and teleportation.
This teleportation feat was announced as one of the first results of these experiments. Not only did the team teleport the first object ever from the ground to orbit, they also created the first satellite-to-ground quantum network, smashing the record for the longest distance for which entanglement has been measured.
“Long-distance teleportation has been recognized as a fundamental element in protocols such as large-scale quantum networks and distributed quantum computation,” says the Chinese team to MIT Technology Review. “Previous teleportation experiments between distant locations were limited to a distance on the order of 100 kilometers, due to photon loss in optical fibers or terrestrial free-space channels.”
What comes to mind when you think of teleportation?
Your brain might conjure images of Scotty beaming up the Enterprise crew in Star Trek, but it's actually quite a different process than sci-fi films present.
Quantum teleportation relies on quantum entanglement — a situation where one set of quantum objects (such as photons) form at the same instant and point in space. In this way, they share the same existence. This shared existence continues even when the photons are separated – meaning a measurement on one immediately influences the state of the other, regardless of the distance between them.
This link can be used to transmit quantum information by "downloading" the information associated with one photon over an entangled link to another photon. This second photon takes on the identity of the first.
In this particular instance, the Chinese team created entangled pairs of photons on the ground at a rate of about 4,000 per second. They then beamed one of these photons to the satellite, and kept the other photon on the ground. Finally, they measured the photons on the ground and in orbit to confirm that entanglement was taking place.
It's worth noting that there are some limits to this technology. Transporting anything large, for instance, is a ways off. In theory, there's also no maximum transportation distance, but entanglement is fragile, and the links can easily be broken.
Despite these limits, this research paves the way for even more ambitious studies of quantum teleportation. “This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet,” says the team.
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