Monolithic Integration of a Quantum Emitter with a Compact On-chip   Beam-splitter
  A fundamental component of an integrated quantum optical circuit is an on-chip beam-splitter operating at the single-photon level. Here we demonstrate the monolithic integration of an on-demand quantum emitter in the form of a single self-assembled InGaAs quantum dot (QD) with a compact (>10 um), air clad, free standing directional coupler acting as a beam-splitter for anti-bunched light. The device was tested by using single photons emitted by a QD embedded in one of the input arms of the device. We verified the single-photon nature of the QD signal by performing Hanbury Brown- Twiss (HBT) measurements and demonstrated single-photon beam splitting by cross-correlating the signal from the separate output ports of the directional coupler. 
N. Prtljaga, R. J. Coles, J. OHara, B. Royall, E. Clarke, A. M. Fox,   and M. S. Skolnick
quant-ph physics.optics