Fig. 1. (a) Microphotograph of nineteen waveguides that are coupled together to be used for CTQWs. (b) The detailed description of the coupling distance z and the coupling space w. (c) Microphotograph of the optical grating that is used for light coupling.

Fig. 2. Experimental set-up of the fiber coupling platform. The continuous-wave pump laser at 775 nm from a Ti:sapphire laser (Coherent MBR 110) is transferred by a single-mode fiber (SMF). A pair of quarter wave plate (QWP) and half wave plate (HWP) is used for phase modification. The PBS is used to separate the photon of different polarizations. Lenses (L) are used to focus the photon into the type II PPKTP for generating 1550 nm photon pairs. The dichroic mirror (DM) and the long pass filter (LPF) are used to purify the pump beams. After walking through the waveguide arrays on the chip, the polarization controller (PC) is used to modify the polarization. All of the photons are detected by SNSPDs and are finally coincidence counted.

Fig. 3. (a) Simulated probability distribution of the single-photon source injected into the central waveguide array as a function of the coupling distance. (b) The calculated (blue) and experimental (red) probability distribution of CTQWs with w=0.3μm and z=100μm.

Fig. 4. (a) Image computation method of CTQWs in a limited region. The calculated (blue) and experimental (red) probability distribution of (b) third port incident, (c) fifth port incident, (d) seventh port incident, and (e) tenth port incident CTQWs with w=0.3μm, z=800μm.