Analysis of satellite-to-ground quantum key distribution with adaptive optics

Abstract

Future quantum communication infrastructures will rely on both terrestrial and space-based links integrating high-performance optical systems engineered for this purpose. In space-based downlinks in particular, the loss budget and the variations in the signal propagation due to atmospheric turbulence effects impose a careful optimization of the coupling of light in single-mode fibers required for interfacing with the receiving stations and the ground networks. In this work, we perform a comprehensive study of the role of adaptive optics (AO) in this optimization, focusing on realistic baseline configurations of prepare-and-measure quantum key distribution (QKD), with both discrete and continuous-variable encoding, and including finite-size effects. Our analysis uses existing experimental turbulence datasets at both day and night time to model the coupled signal statistics following a wavefront distortion correction with AO, and allows us to estimate the secret key rate for a range of critical parameters, such as turbulence strength, satellite altitude and ground telescope diameter. The results we derive illustrate the interest of adopting advanced AO techniques in several practical configurations.

Real-time gigahertz free-space quantum key distribution within an emulated satellite overpass

“…This can be considered to effectively reduce the coupling efficiency to 35% for our experiments. Assuming nighttime operation, this value is realistic to achieve through the use of modern (multiorder) adaptive optics systems (43). By combining η turb , η rx , η coupling , η pat , and η pde , we find the total loss at the QRx to be 8.5 dB (the measured transmission efficiencies are shown in Table 1).…”

“…Furthermore, the coupling efficiency due to turbulence effects will change as a function of the elevation angle, which is not accounted for in this study as we do not expect a large variation for nighttime operation; instead, we have assumed a pessimistic value (expected for low satellite elevations) across the entire pass. However, this variation should be taken into account when daytime operation is under consideration (43).…”

Satellite-based quantum information networks: use cases, architecture, and roadmap

“…We note that single-mode fibre coupling in satellite-to-ground laser links is a tedious task, due to the required correction of aberrations in real time, that has been modelled in refs. [93][94][95] , and implemented in ref. 96 .…”

Experimental effects of turbulence on coherent states in a free-space channel using adaptive optics for continuous variable quantum key distribution

“…8 These aberrations translate to the degradation of the interferometric visibility 9 for CVQKD which decreases the achievable secret key rate (SKR). A solution is adaptive optics (AO) which corrects and compensates the phase and wavefront aberrations, [10][11][12][13][14] and therefore the interferometric visibility. In this work, we study the impact of turbulence, introduced by a heat gun, on the interferometric visibility of transmitted coherent states in a free-space channel.…”