Quantum internet closer: New router transmits data with 99% fidelity

Researchers at Tohoku University have developed a breakthrough photonic quantum router capable of transmitting quantum information with over 99% fidelity and extremely low signal loss (0.06 dB or about 1.3%). This device is compatible with existing telecommunication networks and operates at nanosecond speeds, addressing a major hurdle in building scalable quantum communication systems. The router employs a novel parallelogram-shaped interferometer design that preserves photon polarization while reducing the number of optical components, thereby minimizing signal loss and enhancing stability. In a pioneering demonstration, the router successfully directed entangled photon pairs while maintaining an interference visibility of approximately 97%, confirming its ability to handle complex quantum states crucial for applications like distributed quantum computing and secure quantum communication. This development marks a significant step toward realizing a practical quantum internet, which relies on transmitting quantum data encoded in photons without loss or corruption. The new router combines essential features—low loss, high speed, noise-free operation, and telecom compatibility—making it a foundational component for