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Researchers Have Set A New Quantum Entanglement Distance Record – With Over 20 Miles

An experiment in Germany has set a new entanglement distance record where atoms instead of photons could help shed some light on this universe.

Entanglement was originally brought forward as a concept in the early 20th century as a consequence of quantum mechanics, but it was considered impossible. However, it has been proved that it is possible for particles to be “entangled” such that properties like position, momentum, spin, and polarization can be shared between them. A change in one is immediately reflected in its twin.

Scientists believe entanglement could form the basis for future communication systems that are faster and more secure than the contemporary ones. Researchers from Ludwig-Maximilians-University Munich (LMU) and Saarland University have made a breakthrough in the new experiment.

The aim of the new research was to entangle a pair of rubidium atoms. The two atoms started at a distance of 700m over an optical cable. The team excited the atoms with a laser pulse, which produced photons entangled with each atom. They traveled down the cable to a receiving station where they underwent a joint measurement, thus entangling them with each other. That caused the original atoms to become entangled with each other.

The team then extended the distance between the entangled atoms by unspooling more fiber optic cable, eventually reaching 33 kilometers (20.5 miles). The main element was altering the wavelength of the photons, which have a natural frequency of 780 nm. This wavelength tends to dissipate after several kilometers passing through glass fibers, but shifting the frequency to 1517 nm achieved much better reliability.

Rather than building new infrastructure, it may be possible to use existing fiber optic networks with entanglement-based systems.