The proposal, published by the Institute of Physics and the New Physics Journal today, is surprisingly simple, and exceptional because it requires very little in the way of modification to the ISS.
Basically, the ISS is already equipped with a Nikon camera and 400mm lens (together called NightPod), pointed at the Earth through a 70cm window in the Cupola Module. The European physicists’ proposal would keep the lens in place, but replace the camera with a new, single-photon counting module. This module would be shipped to the ISS aboard a SpaceX Dragon or a Russian Soyuz capsule.
Once the module is in place, a base station here on Earth on will entangle pairs of photons, with one half being kept on Earth, and the other half being transmitted to the ISS.
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).
These experiments will be carried out as the ISS makes overhead passes of the optical ground station. ”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.