Two-photon interference from independent cavity-coupled emitters   on-a-chip
  Interactions between solid-state quantum emitters and cavities are important for a broad range of applications in quantum communication, linear optical quantum computing, nonlinear photonics, and photonic quantum simulation. These applications often require combining many devices on a single chip with identical emission wavelengths in order to generate two-photon interference, the primary mechanism for achieving effective photon-photon interactions. Such integration remains extremely challenging due to inhomogeneous broadening and fabrication errors that randomize the resonant frequencies of both the emitters and cavities. In this letter we demonstrate two-photon interference from independent cavity-coupled emitters on the same chip, providing a potential solution to this long-standing problem. We overcome spectral mismatch between different cavities due to fabrication errors by depositing and locally evaporating a thin layer of condensed nitrogen. We integrate optical heaters to tune individual dots within each cavity to the same resonance with better than 3 {\mu}eV of precision. Combining these tuning methods, we demonstrate two-photon interference between two devices spaced by less than 15 {\mu}m on the same chip with a post-selected visibility of 33%. These results pave the way to integrate multiple quantum light sources on the same chip to develop quantum photonic devices. 
Je-Hyung Kim, Christopher J. K. Richardson, Richard P. Leavitt, and   Edo Waks
quant-ph cond-mat.mes-hall physics.optics