April 10, 2013
Einstein’s Spooky Action Theory Could Be Tested Aboard Space Station
April Flowers for redOrbit.com - Your Universe Online
"Spooky action at a distance" is how Albert Einstein rather famously described the theory of quantum entanglement. Until now, however, experiments attempting to examine this peculiar quantum mechanical phenomenon have been limited to relatively small distances on Earth.
Researchers have proposed a solution to this in a new study published in the New Journal of Physics. To test the limits of Einstein's "spooky action" and potentially help to develop the first global quantum communication network, the researchers propose using the International Space Station (ISS).
The plan consists of several experiments, including a so-called Bell experiment to test the theoretical contradiction between the predictions of quantum mechanics and classical physics, and a quantum key distribution experiment which will use the orbiting lab as a relay point to send a secret encryption key across much larger distances than have already been achieved using optical fibers on Earth.
With only a few overhead passes of the ISS, the team's calculations reveal that "major experimental goals" could be achieved with each of the experiments lasting less than 70 seconds per pass.
"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," Professor Rupert Ursin from the Austrian Academy of Sciences (OAW) said in a statement.
The only new equipment needed for this series of experiments would be a photon detection module that could be sent to the ISS and attached to an already existing Nikon 40mm commercial photographer's lens. The lens sits in a 70-cm window in the Cupola Module, always facing the Earth.
A pair of entangled photons would be created on the ground to start the Bell experiment. One of the photons would be sent from the ground station to the modified camera aboard the Space Station. The other would be measured locally on the ground for comparison.
Even when separated over long distances, entangled photons have an intimate connection with each other. This connection defies the laws of classical physics. No matter how far apart the photons are, a measurement on one of the entangled photons in a pair will determine the outcome of the same measurement on the second photon.
"According to quantum physics, entanglement is independent of distance. Our proposed Bell-type experiment will show that particles are entangled, over large distances -- around [300 miles] -- for the very first time in an experiment," added Professor Ursin. "Our experiments will also enable us to test potential effects gravity may have on quantum entanglement."
The quantum key distribution experiment consists of a secret cryptographic key generated using a stream of photons. The key is shared between two parties with the knowledge that if someone else intercepted it, the interruption would be noticed. Prior to the ISS experiment, the furthest a secret key has been sent is a few hundred miles, allowing communication between just one or two cities.
Globally, research teams have been looking to build quantum satellites that could act as relays between the two parties, drastically increasing the distance that a secret key could be passed. The new proposal claims this relay may be possible by implementing an optical uplink towards the ISS and making a very minor alteration to the camera already on-board.