Non-classical interference in integrated 3D multiports

We demonstrate three and four input multiports in a three dimensional glass platform, fabricated using the femtosecond laser direct-write technique. Hong-Ou-Mandel (HOM) interference is observed and a full quantum characterisation is performed, obtaining two photon correlation matrices for all combinations of input and output ports. For the three-port case, the quantum visibilities are accurately predicted solely from measurement of the classical coupling ratios.