Entanglement-based quantum key distribution for daylight and uplink satellite configuration: proof-of-principle laboratory demonstration and feasibility test
Year: 2026
Type: article
Abstract: Experimental realization of entanglement-based quantum key distribution (QKD) in a daylight-uplink (ground-to-satellite) communication channel is highly challenging due to the very low signal-to-noise ratio (SNR) of this configuration, and it has yet to be successfully implemented to date. While current research efforts focus on weak coherent pulse (WCP) sources for daylight QKD, we present a proof-of-principle laboratory demonstration emulating daylight-uplink QKD in a free-space-fiber hybrid configuration using polarization-entangled photon pairs generated via a spontaneous parametric down-conversion (SPDC) process. The emulated uplink channel attenuation reaches up to 50 dB, equivalent to low-earth-orbit (LEO) distances. Furthermore, the detected noise level (up to a few MHz) in the receiver telescope is representative of daylight conditions. The enhancement of SNR is achieved by implementing rigorous filtering on spatial, spectral, and temporal modes. Our ultra-bright source of entangled photons, characterized by a narrow spectral bandwidth of 0.54 nm FWHM, ensures minimal signal attenuation. Using a theoretical model, we estimate the conditional feasibility of entanglement-based QKD for daylight-uplink LEO satellite links up to approximately 400 km, subject to the experimentally motivated system assumptions adopted in this work, including efficient single-mode fiber (SMF) coupling performance.
Source: Optics Continuum
Institution: Nicolaus Copernicus University
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,372
OpenAlex ID: W7163036897