The implementation of a fully integrated Hadamard gate on one single chip is currently one of the major goals in the quantum computation and communication community. Prerequisites for such a chip are the integration of single-photon sources and detectors into waveguide structures such as photonic crystals or slab and ridge waveguide. Here, we present an implementation of a single-photon on-chip experiment based on a III-V semiconductor platform.Individual semiconductor quantum dots were used as pulsed single-photon sources integrated in ridge waveguides, and on-chip waveguide-beamsplitter operation is verified on the singlephoton level by performing off-chip photon cross-correlation measurements between the two output ports of the beamsplitter. A careful characterization of the waveguide propagation losses (∼ 0.0068 dB/µm) documents the applicability of such GaAs-based waveguide structures in more complex photonic integrated circuits. The presented work marks an important step towards the realization of fully integrated photonic quantum circuits including on-demand single-photon sources.

We use a laser-driven single (In,Ga)As quantum dot (QD) in the dressed state regime of resonance fluorescence (T = 4 K) to observe the four D 1 -transition lines of alkali atomic cesium (Cs) vapor at room temperature. We tune the frequency of the dressing continuous-wave laser in the vicinity of the bare QD resonance ∼ 335.116 THz (∼ 894.592 nm) at constant excitation power and thereby controllably tune the center and side channel frequencies of the probe light, i.e. the Mollow triplet. Resonances between individual QD Mollow triplet lines and the atomic hyperfine-split transitionsare clearly identified in the Cs absorption spectrum. Our results show that narrow-band (In,Ga)As QD resonance fluorescence (RF) is suitable to optically address individual transitions of the D 1 quadruplet without applying magnetic field or electric field tuning.