In a critical step toward creating a global quantum communications network, researchers have generated and detected quantum entanglement onboard a CubeSat nanosatellite weighing less than 2.6 kg and orbiting the Earth.
The University of Strathclyde is involved in an international team which has demonstrated that their miniaturised source of quantum entanglement can operate successfully in space aboard a low-resource, cost-effective CubeSat that is smaller than a shoebox. CubeSats are a standard type of nanosatellite made of multiples of 10 cm × 10 cm × 10 cm cubic units.
The quantum mechanical phenomenon known as entanglement is essential to many quantum communications applications. However, creating a global network for entanglement distribution is not possible with optical fibers because of the optical losses that occur over long distances. Equipping small, standardised satellites in space with quantum instrumentation is one way to tackle this challenge in a cost-effective manner.
The research, led by the National University of Singapore, has been published in the journal Optica.
Dr Daniel Oi, a Senior Lecturer in Strathclyde’s Department of Physics, is the University’s lead on the research. He said: “This research has tested next generation quantum communication technologies for use in space. With the results confirmed, its success bodes well for forthcoming missions, for which we are developing the next enhanced version of these instruments.”
As a first step, the researchers needed to demonstrate that a miniaturised photon source for quantum entanglement could stay intact through the stresses of launch and operate successfully in the harsh environment of space within a satellite that can provide minimal power. To accomplish this, they exhaustively examined every component of the photon-pair source used to generate quantum entanglement to see if it could be made smaller or more rugged.
The new miniaturised photon-pair source consists of a blue laser diode that shines on nonlinear crystals to create pairs of photons. Achieving high-quality entanglement required a complete redesign of the mounts that align the nonlinear crystals with high precision and stability.
The researchers qualified their new instrument for space by testing its ability to withstand the vibration and thermal changes experienced during a rocket launch and in-space operation. The photon-pair source maintained very high-quality entanglement throughout the testing and crystal alignment was preserved, even after repeated temperature cycling from -10 °C to 40 °C.
The researchers incorporated their new instrument into SpooQy-1, a CubeSat that was deployed into orbit from the International Space Station on 17 June 2019. The instrument successfully generated entangled photon-pairs over temperatures from 16 °C to 21.5 °C.
The researchers are now working with RAL Space in the UK to design and build a quantum nanosatellite similar to SpooQy-1 with the capabilities needed to beam entangled photons from space to a ground receiver. This is slated for demonstration aboard a 2022 mission. They are also collaborating with other teams to improve the ability of CubeSats to support quantum networks.
Strathclyde is the only academic institution that has been a partner in all four EPSRC funded Quantum Technology Hubs in both phases of funding. The Hubs are in Sensing and Timing, Quantum Enhanced Imaging, Quantum Computing and Simulation and Quantum Communications Technologies. Dr Oi is Strathclyde’s lead on a forthcoming CubeSat mission being developed by the Quantum Communications Technologies Hub.
Dr Oi is also scientific lead on ROKS, an upcoming satellite mission led by Craft Prospect, a space engineering practice that delivers mission-enabling products and develops novel mission applications for small space missions. ROKS will demonstrate critical quantum technologies and services for QKD. The company is based in the Tontine Building in the Glasgow City Innovation District, which is transforming the way academia, business and industry collaborate to bring competitive advantage to Scotland.