The Quantum Photonics laboratory is attempting to demonstrate the first-ever entangled-photon link between the ground and an orbiting satellite. Dubbed the Quantum Encryption and Science Satellite (QEYSSat), the Quantum Photonics lab is working to develop a space-qualified quantum receiver for this purpose and hopes to use it to demonstrate a communication link between the ground and space that is secured via Quantum Key Distribution (QKD). QKD is a method for securing optical communication lines by using entangled photon-pairs to carry encryption keys between two stations. Entangled photon-pairs with randomly generated polarization states may be used to generate strings of random numbers–the encryption “keys”. The advantage of distributing these keys via entangled photon-pairs is that the uncertainty principle guarantees this signal may not be intercepted and re-transmitted with high fidelity. The presence of an eavesdropper in a QKD system will become immediately apparent as the photon-pairs become disentangled and the error-rate in the communication line increases. The Quantum Photonics laboratory has demonstrated a number of entangled-photon sources and high-sensitivity single photon detectors over the years which will form the building blocks for the proposed ground-to-space QKD link.
The Quantum Photonics lab have demonstrated some notable milestones on the road to space based QKD. Just this past summer the team demonstrated a free-space QKD link between a stationary ground-station and a receiver in a vehicle moving at 33km/h in order to simulate the angular velocity of an orbiting satellite. In 2011 the team successfully demonstrated a QKD link over a high-loss (50dB) channel, simulating the expected loss in a ground-to-space link.
The Quantum Photonics lab has also had tremendous success in the generation of polarization entangled photon pairs and triplets through spontaneous parametric down-conversion. The Quantum Photonics group made waves (particles for you classicists) recently for their demonstration of three-photon polarization entanglement in an experiment which closes the locality loophole. This work was the first of its kind and was able to realize three-photon entanglement between three widely separated locations (> 600m). Professor Jennewein was also a part of the team that, in 2012, demonstrated quantum teleportation over a free-space channel of 143km between two observatories in the Canary islands.