Optical Terminal for Canada's Quantum Encryption and Science Satellite (QEYSSat)

Honeywell Aerospace has been selected by the Canadian Space Agency to implement the Quantum Encryption and Science Satellite (QEYSSat), a Canadian-owned and operated scientific and technology demonstration mission towards the next-generation of secure communications infrastructure. Quantum key distribution (QKD) is a method for distributing, via single-photon transfer, verifiably-confidential encryption keys between two parties separated by large distances. This capability is a powerful tool for the transmission of sensitive data (e.g. financial transactions, personal health records, etc.), however current ground-based QKD networks are limited in geographic reach to roughly 200 kilometres. The QEYSSat mission will use a satellite receiver to demonstrate the distribution of secure keys between ground stations separated by at least 400 km. In addition, Honeywell intends to fly an optical intersatellite link (OISL) terminal as a hosted payload on this mission. The QEYSSat mission will implement both weak coherent pulse (WCP) sources and entangled photon sources to study the performance of QKD, and to perform Bell tests of long-range quantum entanglement. Honeywell is building the free-space QKD terminal consisting of a large-diameter front-end telescope, a precision pointing and tracking system, single-photon receiver, and a downlink source. Major technical challenges include accurate pointing and tracking, polarization-management throughout the optical chain, and deep suppression of background and stray light sources, given the nature of single photon exchange over large distances. To address these challenges, Honeywell is leveraging its existing optical communications solutions to meet the enhanced performance requirements for space-based QKD. A large-format telescope for geostationary optical communications forms the basis for the terminal's front-end optics, and Honeywell's commercially-focused Optical Pointing and Tracking Relay Assembly for intersatellite Communications (OPTRAC) is being adapted as a high-performance, quantum-ready pointing and tracking unit (QTRAC). This paper discusses the design of the QKD terminal and will highlight results from the recently completed QEYSSat Phase A study.