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. Their paper, “All-optical turbulence mitigation for free-space quantum key distribution using stimulated parametric down-conversion,” appears in the journal Optica.
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.”
