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We present a method by which the degree of longitudinal variation in photonic crystal fibre (PCF) may be characterised through seeded four-wave mixing (FWM). Using an iterative numerical reconstruction, we created a theoretical model of the PCF that displays FWM phasematching properties that are similar to experiment across all measured length scales. Our results demonstrate that the structure of our PCF varies by less than ±1 % and that the characteristic length of the variations is approximately 15 cm.

We report a bright and tunable source of spectrally pure heralded single photons in the telecom O-Band, based on cross-polarized four wave mixing in a commercial birefringent optical fiber. The source can achieve a purity of 85%, heralding efficiency of 30% and high coincidences to accidentals ratio of 108. Furthermore, the possibility of building multiple identical sources is explored. Through the measurements of joint spectral intensities, we find that the fiber is homogeneous over atleast 45 centimeters and can potentially realize 4 identical sources. This paves the way for a cost-effective fiber-optic approach to implement multi-photon quantum optics experiments. * Electronic address: jasleen.

We report a single-stage bi-directional interface capable of linking Sr + trapped ion qubits in a longdistance quantum network. Our interface converts photons between the Sr + emission wavelength at 422 nm and the telecoms C-band to enable low-loss transmission over optical fiber. We have achieved both up-and down-conversion at the single photon level with efficiencies of 9.4 % and 1.1 % respectively. Furthermore we demonstrate noise levels that are low enough to allow for genuine quantum operation in the future.