Simultaneous Faraday filtering of the Mollow triplet sidebands with the Cs-D1 clock transition

Hybrid quantum systems integrating semiconductor quantum dots (QDs) and atomic vapours become important building blocks for scalable quantum networks due to the complementary strengths of individual parts. QDs provide on-demand single-photon emission with near-unity indistinguishability comprising unprecedented brightness—while atomic vapour systems provide ultra-precise frequency standards and promise long coherence times for the storage of qubits. Spectral filtering is one of the key components for the successful link between QD photons and atoms. Here we present a tailored Faraday anomalous dispersion optical filter based on the caesium-D 1 transition for interfacing it with a resonantly pumped QD. The presented Faraday filter enables a narrow-bandwidth (Δ ω =2 π × 1 GHz) simultaneous filtering of both Mollow triplet sidebands. This result opens the way to use QDs as sources of single as well as cascaded photons in photonic quantum networks aligned to the primary frequency standard of the caesium clock transition. Hybrid quantum systems combine efficient high-quality quantum dot sources with atomic vapours that can serve as precise frequency standards or quantum memories. Here, Portalupi et al . demonstrate an optimized atomic Cs-Faraday filter working with single photons emitted from a semiconductor quantum dot.