Supervisor's Foreword; Abstract; Publication ListRobert J.A. Francis-Jones, Rowan A.Hoggarth and Peter J. Mosley, All-fibre multiplexed source of high-purity single photons, Optica, 3(11), pp. 1270-1273 (2016).Robert J.A. Francis-Jones and Peter J. Mosley, Characterisation of longitudinal variation in photonic crystal fibre, Optics Express, 24(22), pp. 24863-24845 (2016).Robert J.A. Francis-Jones and Peter J. Mosley, An all-fibre low-noise source of pure heralded single photons, In Preparation (2016).Robert J.A. Francis-Jones, ; Acknowledgements; Contents; Acronyms; Mathematical Variables

1 Introduction1.1 What Is a Photon?; 1.1.1 Indistinguishability and Hong-Ou-Mandel Interference; 1.2 Methods of Single Photon Generation; 1.2.1 Single Emitter Sources; 1.2.2 Heralded Single Photon Sources; 1.3 Multiplexing: A Route to Deterministic Operation; 1.4 Thesis Outline; References; 2 Photon Pair Generation via Four-Wave Mixing in Photonic Crystal Fibres; 2.1 Overview; 2.2 Photon Pair Generation in Photonic Crystal Fibres; 2.3 Spectral Engineering of the Two-Photon State; 2.4 Reduced State Spectral Purity: Schmidt Decomposition; 2.5 Photon Number Statistics; 2.5.1 Raman Scattering

2.5.2 Degree of Heralded Second Order Coherence2.5.3 Degree of Marginal Second Order Coherence; References; 3 Numerical Modelling of Multiplexed Photon Pair Sources; 3.1 Overview; 3.2 The Building Blocks; 3.2.1 Pair Generation; 3.2.2 Detection; 3.2.3 Metrics and Measurements; 3.3 Spatial Multiplexing; 3.3.1 Simulation Results and Discussion; 3.4 Temporal Loop Multiplexing; 3.4.1 Simulation Results and Discussion; 3.5 Conclusion; References; 4 Design, Fabrication, and Characterisation of PCFs for Photon Pair Generation; 4.1 Overview; 4.2 Photonic Crystal Fibre Design and Fabrication

4.2.1 Simulation and Design4.2.2 PCF Fabrication and Characterisation; 4.3 Measuring the Joint Spectral Intensity Distribution; 4.3.1 Stimulated Emission Tomography of FWM; 4.4 The Effect of PCF Inhomogeneity on the Reduced State Purity; 4.4.1 Numerical Reconstruction of Inhomogeneous PCFs; 4.4.2 The Final Fibres; 4.5 Conclusions; References; 5 Construction of an Integrated Fibre Source of Heralded Single Photons; 5.1 Overview; 5.2 Photonic Bandgap Fibre Filter Design and Fabrication; 5.3 Component Assembly and Splicing; 5.3.1 PCF-SMF Splicing; 5.3.2 PBGF-SMF Splicing

5.3.3 Assembly of the Photon Pair Source5.4 Detection and Coincidence Counting Electronics; 5.5 Optical Switch Integration; References; 6 Characterisation of a Multiplexed Photon Pair Source; 6.1 Overview; 6.2 Characterisation of the Coincidence Count Rates; 6.2.1 Coincidence Counting and Coincidence-to-Accidentals; 6.2.2 Experimental Results: Coincidences and CAR ; 6.2.3 Experimental Results: Source 2 Noise Gating; 6.3 Characterisation of the Second Order Coherence; 6.3.1 Experimental Results: Marginal Second Order Coherence; 6.3.2 Experimental Results: Heralded Second Order Coherence