Entanglement swapping between independent and asynchronous integrated photon-pair sources

Abstract: Integrated photonics represents a technology that could greatly improve quantum communication networks in terms of cost, size, scaling, and robustness. A key benchmark for this is to demonstrate their performance in complex quantum networking protocols, such as entanglement swapping between independent photon-pair sources. Here, using time-resolved detection, and two independent and integrated Si$3$N$_4$ microring resonator photon-pair sources, operating in the CW regime at telecom wavelengths, we obtained spectral purities up to $0.97 \pm 0.02$ and a HOM interference visibility between the two sources of $V{\rm HOM}=93.2 \pm 1.6\,\%$. This results in entanglement swapping visibility as high as $91.2 \pm 3.4\,\%$