Photon-photon correlation: milestones in quantum optics

Zhongkan Tang, Rakhitha Chandrasekara, Yue Chuan Tan +5 more

Progress in quantum computers, and their threat to conventional public-key infrastructure, drives new forms of encryption, including quantum key distribution using entangled photons. Beaming entangled photons to Earth from orbit could provide secure quantum communication over long distances. The authors transform a large, delicate quantum-optics setup into a robust payload for a shoebox-sized CubeSat satellite. Their gear survives the trip to space, and correlated photons are produced and detected aboard the satellite, validating the design---a milestone on the road to a space-based quantum communications network.

John Rarity, P. R. Tapster

Augusto Garuccio

Rakhitha Chandrasekara, Zhongkan Tang, Yue Chuan Tan +3 more

Secured global quantum communication networks sharing an encryption key can be established with entangled photon sources onboard satellites in Earth orbit. Even though optical transceivers for ground-to-space communication exist, no space capable source of entangled photons has been demonstrated. A faster and cost-effective solution to reach orbit is by means of CubeSats. This demands significant miniaturisation work on the photon source to fit within the size, weight and power restrictions of CubeSats. The first milestone in our programme is to deploy a source of correlated photon pairs in space as a pathfinder experiment to demonstrate the principle and raise the technology readiness level. The first attempt was unsuccessful when the launch vehicle (CRS Orb-3) failed shortly after take-off, although our payload was successfully recovered intact and found to be fully operational. We are pleased to report that the second attempt with a newly built payload, has been successful and the first milestone has been accomplished. The source was launched on board the Galassia CubeSat (PSLV C29) to an orbit of approximately 550 km and 150 inclination. We observed inorbit generation of high quality photon pair correlations (with a contrast of 97 ± 2%). These results are compatible with baseline data collected prior to launch and show no degradation after spending 140 days in orbit. Data will be presented on the effects of temperature and radiation on the source performance. We will also present plans for upcoming and future missions.

Zhongkan Tang, Rakhitha Chandrasekara, Yue Chuan Tan +3 more

We report the operation of a photon pair source on board a nanosatellite. Pair generation and polarization correlation are demonstrated in low Earth orbit: an important milestone towards compact entangled photon pair sources for future space-based quantum communication.

Rupamanjari Ghosh