We successfully produce Josephson junctions by stacking NbSe2 flakes, where the twist angle and strain are responsible for a weak link. Field sweep measurements are taken to characterize these...Show moreWe successfully produce Josephson junctions by stacking NbSe2 flakes, where the twist angle and strain are responsible for a weak link. Field sweep measurements are taken to characterize these devices. These measurements highlight the importance of the direction of the applied magnetic field. Prompted by this, simulations of the critical current given an arbitrarily shaped interface area are presented and compared to measurements.Show less
Multiport interferometers are an important tool in the emerging field of quantum information technologies. In theoretical work, we investigate implementing Haar-random unitary transformations in...Show moreMultiport interferometers are an important tool in the emerging field of quantum information technologies. In theoretical work, we investigate implementing Haar-random unitary transformations in increasingly large interferometers with realistic imperfections. We find that random matrices result in mostly low values of interferometer beam splitter reflectivities. We model production imperfections and we find that these severely limit the implementation of random matrices. We show the effects of the imperfection can be mitigated through optimisation of interferometer degrees of freedom and by adding additional beam splitters. In experimental work, we investigate the realisation of reconfigurable multiport interferometers in silica-on-silicon integrated photonics chips using a modular design. We show that individual modules are fully reconfigurable. We give a proof-of-principle of the design by connecting three modules for the first time and measure 5% transmission.Show less
We observe spatial bunching of four spatially entangled photons produced by parametric down-conversion in a single periodically poled KTP crystal. This effect involves an increased probability to...Show moreWe observe spatial bunching of four spatially entangled photons produced by parametric down-conversion in a single periodically poled KTP crystal. This effect involves an increased probability to generate all four photons in the same optical mode. To observe the effect we create entangled double pairs at 826 nm wavelength using a 5 mm long crystal and investigate their correlations by measuring three-fold coincidence counts. We demonstrate that two-fold and three-fold coincidence measurements are sufficient to experimentally distinguish a spatially entangled two-photon state from a four-photon state and a four-photon state from a six-photon state, respectively. This makes experimental observation of the effect feasible at moderately high pump-powers.Show less
