Record-setting quantum entanglement connects two atoms across 20 miles
TL;DR
Researchers in Germany achieved quantum entanglement between two atoms over 33 kilometers of fiber optics, breaking the distance record. This experiment, using rubidium atoms and photons, brings us closer to creating a secure quantum internet that operates over existing fiber optic networks. By converting photons to a longer wavelength, the team reduced data loss over long distances. The success shows that a quantum internet could utilize existing fiber optic infrastructure for secure communication.
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Researchers in Germany have successfully demonstrated quantum entanglement between two atoms that were separated by 33 kilometers (20.5 miles) of fiber optic cable. This achievement sets a new distance record for this type of communication and represents a significant advancement toward the development of a fast and secure quantum internet.
Quantum entanglement is a strange phenomenon where two particles can become so closely connected that observing one reveals information about the other. Even more bizarre, changing something about one particle instantly affects its partner, no matter how far apart they are. This has led to the unsettling idea that information is being “teleported” faster than the speed of light, a concept that even Einstein struggled with, famously referring to it as “spooky action at a distance.”
Despite seeming impossible, quantum entanglement has been consistently demonstrated in experiments over the past few decades. Scientists have been utilizing its unusual properties to transmit data quickly across long distances. In a new study, researchers from Ludwig-Maximilians-University Munich (LMU) and Saarland University have now set a new distance record for quantum entanglement between two atoms using fiber optics.
In the experiment, the researchers entangled two rubidium atoms, which were kept in optical traps located in different buildings on the LMU campus. These atoms were initially separated by 700 meters (2,297 feet) of fiber optic cable, which was later extended to 33 kilometers using extra spools of fiber. Each atom was excited by a laser pulse, causing it to emit a photon that became quantum entangled with the atom.
The photons were then sent through the fiber optic cables to a central receiving station. At this station, the photons underwent a joint measurement, entangling them together. Since each photon was already entangled with its respective atom, the two atoms also became entangled with each other.
Although photons have been entangled over long distances before, this experiment set a new distance record for entangling two atoms over fiber optics, which could act as “quantum memory” nodes. The researchers achieved this by converting the photons to a longer wavelength, enabling them to travel farther through the fiber optic cables. The natural wavelength of 780 nanometers (nm) would cause the photons to be lost after just a few kilometers, so the team used a device to shift the wavelength to 1,517 nm, which is closer to the 1,550-nm wavelength used in fiber optic telecommunications, reducing signal loss.
According to the researchers, this experiment is a crucial step toward creating a functional quantum internet. Such a network would be much faster and more secure than today’s communication systems. Notably, this study demonstrates that quantum communication can operate over the existing fiber optic infrastructure. This technology could also be combined with satellites, which have already been used to send entangled photons over thousands of kilometers.
The research was published in the journal Nature.
