Quantum Internet: First Teleportation to a Solid-State Quantum Memory
Via MIT Technology Review.
Quantum teleportation is the ability to transmit from one location to another without traveling through the space in between. Matter itself doesn’t make this journey, only the information that describes it. This is transmitted to a new body that takes on the identity of the original.
But while science fiction fans have focused on body involved, quantum physicists are more interested in the information. For them, teleportation is the enabling technology behind a new generation of information processing technologies including a quantum Internet that allows information to be transmitted with perfect security.
One of the building blocks of the quantum Internet will be quantum routers that can receive quantum information from location and route it on to another without destroying it. So the race is on to demonstrate this kind of technology, which has the potential to revolutionize communications.
Today, Felix Bussières at the University of Geneva in Switzerland and a few pals say they’ve taken an important step towards this. These guys have teleported quantum information to a crystal doped with rare-earth ions—a kind of quantum memory. But crucially they’ve done it for the first time over the kind of ordinary optical fiber that telecommunications that are in use all over the world.
One of the main requirements for widespread teleportation is entangled photons with a wavelength compatible with telecom fiber. That’s not so easy to produce since the entangled photons must be compatible with the discrete energy jumps in the quantum memory. “This wavelength is typically far away from the low-loss region of standard optical fiber,” say Bussières and co.
So the trick these guys have perfected is to generate entangled pairs of photons with different wavelengths. The first has a wavelength of 883nm (near-infrared), which is compatible with a type of quantum memory made of neodymium-doped yttrium orthosilicate crystals. The second has a wavelength of 1338nm (mid infrared), which passes easily through telecoms optical fiber.
The quantum state to be teleported is the polarization of a 1338nm photon. So these guys send the 883nm signal to the quantum memory where it is stored while transmitting the 1338 signal through a 12 km fiber to another apparatus that prepares a third photon (also at 1338 nm) with the polarization to be teleported.
This is when the teleportation takes place. When these two 1338nm photons are made to interact in a certain way, the polarization is teleported to the quantum memory at the other end of the experiment.
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