Generating entangled photons on monolithic chips

Generating entangled photons on monolithic chips is a significant progress towards real-life applications of optical quantum information processing such as quantum key distribution and quantum computing. Here we present our recent achievements in generating polarization entangled photons on monolithic III-V semiconductor chips without any off-chip component. We demonstrate the direct generation of broadband polarization entangled photons from a semiconductor chip for the first time with a record degree of entanglement. We also show an alternative approach for polarization entangled photon generation on the same epitaxial structure, which enabled a single chip generating both co-polarized and cross-polarized entangled photons. With recent progress on pump laser integration, our results pave the way for fully integrated entangled photon sources in the foreseeable future.