A team of physicists from the Hebrew University of Jerusalem has achieved a key breakthrough in quantum communication, proposing a new method that brings secure quantum communication closer to real-world applications without relying on perfect hardware. The research, led by PhD students Yuval Bloom and Yoad Ordan under the supervision of Professor Ronen Rapaport at the Racah Institute of Physics, in collaboration with researchers from Los Alamos National Laboratory, has been published in PRX Quantum.

For the past forty years, quantum key distribution (QKD) technology has relied on “perfect single-photon sources” to achieve unconditionally secure communication, but such devices are extremely difficult and costly to manufacture. Traditional approaches have instead used lasers, but uncontrollable multi-photon events in light pulses limit both security and transmission distance. Addressing this pain point, the research team innovatively developed two protocols compatible with existing photon sources: a sub-Poissonian photon source technology based on quantum dots. By dynamically tuning the optical properties of quantum dots and matching them with nano-antennas, the team achieved precise control over photon emission and validated two encryption strategies: the “decoy-state truncation protocol” and the “purification protocol.” The former eliminates multi-photon vulnerabilities to enhance security, while the latter optimizes signal quality by real-time filtering of redundant photons. Experimental results show that the new method improves the secure key exchange distance by more than 3 dB compared to conventional laser-based schemes, setting a new benchmark in the field.

To verify practical feasibility, the team built a real quantum communication device using a room-temperature quantum dot source and implemented an enhanced version of the BB84 encryption protocol. The results demonstrate that the method is compatible with various quantum light sources and significantly outperforms existing technologies in performance, with the potential to substantially reduce the cost and technical barriers for large-scale deployment. Professor Ronen Rapaport stated: “This breakthrough shows that excellent performance does not require perfect hardware—the key lies in more efficient utilization of existing resources.” Co-lead author Yuval Bloom added: “The research paves the way for secure and economical quantum networks in the real world and can immediately leverage resources already available in laboratories worldwide to advance practical implementation.”