The telecom quantum dot source operates at about 76 million photons per second and maintains an average quantum bit error rate below 11% after 120 km, yielding an average secure key rate of roughly 15 bits per second under finite-key conditions.

This work demonstrates the integration potential of telecom-band quantum dot single-photon sources into stable, field-deployable time-bin QKD systems, marking progress toward scalable quantum-secure communications.

The system deterministically and randomly generates three distinct time-bin qubit states from polarized single photons via a self-stabilized encoder, while decoding is performed by an actively stabilized interferometer that includes a phase shifter.

Time-bin encoding offers robustness against environmental fluctuations like turbulence, temperature changes, and vibrations, reducing reliance on heavy compensation in practical channels.

The study, published in Light: Science & Applications on February 25, 2026, is titled Time-bin encoded quantum key distribution over 120 km with a telecom quantum dot source, and involves authors from German and Chinese institutions with support from multiple German and European funding programs.

A time-bin quantum key distribution system using telecom-wavelength quantum dots achieves secure communication over more than 120 kilometers of standard optical fiber, with stable performance lasting over six hours.