Scientists have developed a new method of encrypting satellite-based communication by generating quantum-entangled photons in a spectral range of light.
An international research team has developed a new method for generating and detecting quantum-entangled photons at a wavelength of 2.1 micrometres. Entangled photons are used in encryption methods such as quantum key distribution to ensure the secure telecommunications between two parties.
Using nonlinear crystal to secure satellite communication
For their initial experiment, the team used a nonlinear crystal made of lithium niobate. They sent ultrashort light pulses from a laser into the crystal and a nonlinear interaction produced the entangled photon pairs with the new wavelength of 2.1 micrometres.
Published in the journal Science Advances, the research describes the details of the experimental system and the verification of the entangled photon pairs: “The next crucial step will be to miniaturise this system by converting it into photonic integrated devices, making it suitable for mass production and for the use in other application scenarios”, says Kues.
How was telecommunication previously secured?
Prior to this study, it was only possible to implement such encryption mechanisms with entangled photons in the near-infrared range of 700 to 1550 nanometres. These shorter wavelengths are disturbed by light-absorbing gases in the atmosphere as well as the background radiation of the sun. Without the work of this international research team, end-to-end encryption of transmitted data can only be guaranteed at night, weather permitting.
Led by Dr Matteo Clerici from the University of Glasgow, the international team aims to solve this problem with its discovery. According to Professor Dr Michael Kues from the PhoenixD Cluster of Excellence at Leibniz University of Hannover, the photon pairs entangled at two micrometre wavelength would be significantly less influenced by the solar background radiation. So-called transmission windows exist in the earth’s atmosphere, especially for wavelengths of two micrometres, so that the photons are less absorbed by the atmospheric gases, in turn allowing a more effective communication.