Directional telecom photons from a chirally coupled quantum dot

As quantum information processing moves toward scalable, integrated architectures, there is a critical need for light-matter interfaces that can operate at telecom wavelengths. While chiral quantum optics—where an emitter's spin state dictates the direction of photon emission—has been demonstrated in various systems, achieving this at telecom wavelengths (1260–1360 nm) while maintaining compatibility with silicon photonics has remained a significant challenge.

The researchers developed an integrated photonic platform using self-assembled indium arsenide (InAs) quantum dots embedded in an indium phosphide (InP) microdisk. By utilizing the whispering-gallery-mode resonances of the microdisk, they created a chiral interface. To control the emission, they applied a strong out-of-plane magnetic field, which induces Zeeman splitting in the quantum dot transitions. This allows the researchers to tune the quantum dot into resonance with the cavity and observe the resulting directional emission into the waveguide-coupled ports.

The study reports a peak cavity enhancement of 3.3 and an emission directionality of 0.985. By measuring the directional contrast as a function of the applied magnetic field, the team demonstrated that the system reaches near-ideal chiral coupling at high magnetic fields. This performance level meets the thresholds required for several key quantum protocols, including controlled-NOT gates, Bell-state analyzers, and quantum network architectures. The results confirm that this platform is a viable candidate for high-fidelity quantum information processing in the telecom O-band.

This work bridges the gap between fundamental chiral quantum optics and practical, fiber-compatible quantum technologies. By achieving high-efficiency directional emission in the telecom band, this platform provides a scalable path toward building complex, integrated quantum photonic circuits that can interface directly with existing telecommunication infrastructure.