(ORDO NEWS) — German researchers have demonstrated the quantum entanglement of two atoms separated by 33 km of optical fiber.
This is a record distance for this kind of communication and marks a huge step towards a fast and secure quantum internet.
Never before have scientists been able to entangle atoms at such a great distance. Here’s how they were able to do it
Quantum entanglement is a phenomenon in which two particles can become so inextricably linked that by studying one particle, you change the state of the other.
A change in the state of one particle is transmitted to the other instantly, no matter how far apart they are.
This leads to the disturbing conclusion that information is “teleported” faster than the speed of light, an idea that was too frightening even for Einstein, who famously described it as “creepy action at a distance”.
Record quantum entanglement
In their experiments, the team of physicists entangled two rubidium atoms that were optically trapped in two different buildings on the Ludwig Maximilian University of Munich campus.
They were separated by 700 meters of fiber optics, which was extended to 33 km with additional cable spools.
Both atoms were excited by a laser pulse, which causes the atom to emit a photon that is quantum entangled with the atom.
The photons are then sent down fiber optic cables to meet at a receiving station in the middle. There, the photons get entangled and since each of them is already entangled with its own atom, the two atoms also bond with each other.
Photons (massless particles) have previously been able to entangle at large distances, but this study sets a new record for the entanglement distance of two atoms (having a rest mass) that could function as “quantum memory” nodes, via fiber optics.
The key is that the intermediary photons have been converted to longer wavelengths to travel farther down the fibers – their natural wavelength of 780 nanometers means they usually scatter after a few kilometers, so physicists increased their wavelength to 1517 nm before starting the journey.
This is close to the 1550 nm wavelength commonly used for telecommunications in fiber optics and reduces signal loss.
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