# Deterministic and highly indistinguishable single photons in the telecom C-band

## TL;DR

Researchers created a reliable source of nearly identical single photons at telecom wavelengths, a key step for quantum communication.

## Contribution

A quantum dot-based single-photon source in the telecom C-band with 91.7% two-photon interference visibility is demonstrated.

## Key findings

- A quantum dot in InAlGaAs achieved 91.7% two-photon interference visibility in the telecom C-band.
- The device uses a circular Bragg grating resonator to enhance performance.
- Multiple optical excitation schemes were tested to optimize coherence and photon quality.

## Abstract

Quantum dots are promising candidates for deterministic single-photon sources, yet achieving high photon indistinguishability at telecom wavelengths remains a critical challenge. Here, we report a quantum dot-based single-photon source operating in the telecommunications C-band that achieves a raw two-photon interference visibility of up to (91.7 ± 0.2)%, thus setting a new benchmark for indistinguishability in this spectral range. The device consists of an indium arsenide (InAs) quantum dot embedded within indium aluminum gallium arsenide (InAlGaAs) and integrated into a circular Bragg grating resonator. We explore multiple optical excitation schemes to optimize coherence and source performance. The demonstration of two-photon interference visibilities exceeding 90% from a quantum-dot emitter in the telecommunications C-band pushes solid-state single-photon sources further towards practical quantum communication and quantum networks.

Solid-state quantum emitters in the telecom C-band hold promise for quantum communication applications, but achieving high photon indistinguishability remains challenging. Here, the authors deterministically generate highly indistinguishable single photons in the telecom C-band from InAs/InAlGaAs quantum dots.