Cumulative generation of maximal entanglement between spectrally distinct qubits using squeezed light

Abstract: We demonstrate how to create maximal entanglement between two qubits that are encoded in two spectrally distinct solid-state quantum emitters embedded in a waveguide interferometer. The optical probe is provided by readily accessible squeezed light, generated by parametric down-conversion. By continuously illuminating the emitters, the photon scattering and incremental path-erasure builds up entanglement. Our method does not require perfectly identical emitters, and accommodates spectral variations due to the fabrication process. Furthermore, for some line-width and energy ratios, the entanglement build-up can be significantly faster than for more similar emitters. It is also robust enough to create entanglement with a concurrence above 99\% in the event of scattering losses and detector inefficiencies, and can form the basis for practical entangled networks.