A University of Ottawa team has developed a new way to protect free-space quantum key distribution (QKD) from atmospheric turbulence, one of the main causes of distortion and errors when sending quantum information through air.
Instead of relying on complex, expensive digital adaptive optics, the researchers use a nonlinear optical process called “stimulated parametric down-conversion (StimPDC)”. The technique leverages StimPDC’s phase-conjugation property to correct spatial-mode distortions dynamically without requiring prior knowledge of the turbulent channel.
“We found the idea of using a fundamental optical process to correct the effects of turbulence in real time to be both innovative and largely unexplored,” said Aarón Cardoso, lead author and Quantum Optics Student Researcher at uOttawa. “Our results show we can reduce quantum error rates below the security threshold even under strong turbulence.”
Both theory and experiments were conducted at uOttawa’s Advanced Research Complex (ARC). This work was made possible through the long-standing collaboration between the research groups affiliated with the Max Planck–uOttawa Centre for Extreme and Quantum Photonics and the Nexus for Quantum Technologies institute (NexQT). The results point toward simpler, lower-cost quantum communication systems that could help strengthen long-term digital security.
Their findings, described in the paper “All-optical turbulence mitigation for free-space quantum key distribution using stimulated parametric down-conversion,” appeared in the journal Optica.