On-demand telecom photon source sets record 92% interference

Researchers at the University of Stuttgart have developed a deterministic single-photon source operating in the telecom C-band (around 1550 nanometers) that achieves a record-high photon indistinguishability of nearly 92%. This breakthrough addresses a major challenge in photonic quantum technology: producing on-demand photons that are both identical and compatible with existing fiber-optic communication networks. Prior deterministic sources in this wavelength range had only reached about 72% interference visibility, insufficient for demanding quantum applications, while probabilistic sources, though more indistinguishable, lack synchronization capabilities. The team used indium arsenide quantum dots embedded in indium aluminium gallium arsenide within a circular Bragg grating resonator to enhance photon emission efficiency. They discovered that lattice vibration-mediated excitation minimized noise and preserved photon coherence better than traditional optical pumping. This advancement enables scalable quantum technologies requiring synchronized, indistinguishable photons, such as measurement-based quantum computing and quantum repeaters for long-distance secure communication. By overcoming a decade-old bottleneck