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An artist's conception shows the International Space Station in the midst of an experiment in quantum entanglement.

By Clara Moskowitz LiveScience

"Spooky" quantum entanglement connects two particles so that actions performed on one reflect on the other. Now, scientists propose testing entanglement over the greatest distance yet via an experiment on the International Space Station.

Until now, entanglement has been established on relatively small scales in labs on Earth. But now physicists propose sending half of an entangled particle pair to the space station, which orbits about 250 miles (400 kilometers) above the planet.

"According to quantum physics, entanglement is independent of distance," physicist Rupert Ursin of the Austrian Academy of Sciences said in a statement. "Our proposed Bell-type experiment will show that particles are entangled, over large distances around 500 kilometers for the very first time in an experiment."

Ursin and his colleagues detail the proposed experiment on Monday in the New Journal of Physics, published by the Institute of Physics and the German Physical Society. [Wacky Physics: The Coolest Little Particles in Nature]

Tests of quantum entanglement are called Bell tests after the late Northern Irish physicist John Bell, who proposed real-world checks of quantum theories in the 1960s. Entanglement is one of the weirdest quantum predictions, positing that entangled particles, once separated, can somehow "communicate" with each other instantly. The notion unsettled Albert Einstein so much he famously called it "spooky action at a distance."

To better understand entanglement and test its limits, the researchers suggest flying a small device called a photon detection module to the International Space Station, where it could be attached to an existing motorized Nikon 400mm camera lens, which observes the ground from the space station's panoramic Cupola window.

Once the module is installed, the scientists would entangle a pair of light particles, called photons, on the ground. One of these would then be sent from a ground station to the device on the orbiting lab, which would measure the particle and its properties, while the other would stay on Earth. If the particles keep their entangled state, a change to one would usher in an instant change to the other. Such a long-range test would allow the physicists to probe new questions about entanglement.

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Space station could test 'spooky' entanglement over record distance