Scientists at Tohoku University have unveiled a next-generation photonic router capable of directing quantum information with an accuracy exceeding 99%—a milestone regarded as crucial in the development of the future quantum internet. The device achieves record-low losses of just 0.06 dB (around 1.3%) while remaining fully compatible with existing telecommunications infrastructure, addressing a long-standing challenge of creating practical components for scalable quantum communication.
The system operates at nanosecond speeds and, for the first time, has demonstrated the ability to reroute entangled photon pairs without breaking their quantum correlation. During testing, interference visibility reached 97%, confirming that the router processes complex states while preserving the information encoded within them. Importantly, the device is designed to integrate seamlessly with current fiber-optic networks.
Entanglement remains a cornerstone resource for quantum technologies, essential for distributed computing, high-precision sensing, and secure data transmission. Thus, the ability to maintain entanglement during routing is a fundamental prerequisite for real-world applications. The high interference visibility observed in the Tohoku experiments demonstrates that the new device meets these stringent demands.
The vision of a quantum internet is built upon transmitting information via individual photons. The primary engineering challenge lies in designing components capable of rerouting these fragile particles without distortion. To be universally applicable, such devices must function reliably across a variety of states, with polarization—the orientation of a photon’s electric field—being the most common encoding method.
Until recently, no component could route photons of arbitrary polarization at standard wavelengths with both low loss and high fidelity. The research team led by Professor Fumihiro Kaneda has solved this problem with an electro-optical router. In their experiments, polarization was preserved with greater than 99% accuracy, producing an output signal nearly indistinguishable from the original.
This breakthrough was made possible by an innovative design centered on a parallelogram-shaped interferometer, which preserves polarization while reducing the number of optical components. Fewer elements mean lower losses and greater stability. The result is a device that combines minimal distortion, nanosecond-scale performance, negligible noise, and compatibility with existing networks.
Researchers emphasize that earlier prototypes suffered from noise, distortion, and significant loss, rendering them unsuitable for practical use. By overcoming these limitations in a single solution, the Tohoku University team has taken a decisive step toward building a full-scale quantum network infrastructure, bringing the long-anticipated quantum internet closer to reality.
