Investigating large quantum states with telecommunication-band integrated photonics

Thesis

In this thesis, I generate, characterize, and utilize quantum states with up to eight photons. In particular, I measure the interference of heralded two-photon Fock states, which has not been possible before this work. My results demonstrate that these states provide increased measurement precision compared to coherent states, a result that is of great interest for the field of quantum metrology. To investigate this, I built photon sources at telecom wavelengths, minimised optical loss, and integrated these sources with single-photon number resolving detectors. Specifically, I used periodically poled KTP waveguides for my spontaneous parametric downconversion sources and worked with superconducting photon num- ber resolving transition edge sensors. This enabled me to characterise my source to a very high level of detail, by measuring and analysing the result- ing joint photon number statistics. From a single measurement, I am able to infer all significant parameters describing the properties of the photon source including noise contributions, determine relative weights and give an accurate measure of the systems overall efficiency. Further, I developed an innovative theory, which accurately predicts the measurement results using actual experimental parameters. Based on this theory, I am able to suggest immediate next steps to further increase the performance of my setup. This work paves a route towards new approaches to studying ‘high’ photon number states for quantum metrology.

Authors: Moore, M

• DOI: 10.5287/ora-erk29prdp
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English