Large-scale quantum dot-lithium niobate hybrid integrated photonic circuits enabling on-chip quantum networking

Hybrid integrated quantum photonics offers a scalable route to chip-based quantum networks by combining solid-state quantum dots (QDs) with low-loss and reconfigurable photonic circuits. However, limited integration scalability, spectral inhomogeneity of QD emissions and the challenge of achieving quantum interference between independent sources have impeded progress towards this goal. Here we demonstrate a hybrid lithium niobate photonic platform integrating arrays of QD-containing waveguides with 20 deterministic single-photon sources. Leveraging the piezoelectric properties of thin-film lithium niobate, we develop a circuit-compatible local strain-tuning technique that enables on-chip spectral tuning of individual QDs by up to 7.7 meV. This capability allows quantum interference with a visibility of 0.73 between two spatially separated waveguide-coupled QD single-photon sources, thereby establishing a functional on-chip quantum network. The large-scale integration of tunable and interconnected QD-based single-photon sources within low-loss lithium niobate circuits paves the way for realizing compact and scalable quantum networks on a photonic chip.