World's Largest Quantum Network Between Earth and ISS May be Tested
Albert Einstein famously described quantum entanglement as "spooky action at distance", but now a group of European researchers has proposed the largest quantum network yet: Between Earth and the International Space Station.
In a new study published April 9, 2013, in the Institute of Physics and German Physical Society's New Journal of Physics, researchers have proposed using the International Space Station (ISS) to test the limits of this "spooky action" and potentially help to develop the first global quantum communication network.
Such a network would see entangled photons transmitted over a distance of 250 miles - two or three times greater than previous quantum communication experiments. One of the pair of entangled photons would then be transmitted nearly 155 miles to the ISS, where scientists could compare the state of the photons.
Once entangled, each photon should react to changes in the other's quantum spin - if one switches from up-spin to down-spin, the other should hypothetically do the same, instantly and regardless of the distance between them.
The physicists propose two experiments. The first is a standard Bell-type experiment, which confirms that the entangled photons are indeed under the governance of quantum physics, rather than classical physics (which strictly doesn't allow for these quantum entangled shenanigans). The second experiment would see the transmission of a quantum cryptography key, to see if it's viable to secure conventional communications with space-based quantum key distribution (QKD).
"During a few months a year, the ISS passes five to six times in a row in the correct orientation for us to do our experiments. We envision setting up the experiment for a whole week and therefore having more than enough links to the ISS available," says Rupert Ursi, co-author of the proposal.