Polarised single photons from a cavity-enhanced atom-light interface in photonic quantum networks

Thesis

For quantum computation the efficient preparation and connection of multiple qubits must be addressed. This includes linear optical quantum computation and quantum networks of stationary nodes interlinked by flying qubits. A quantum emitter coupled to a single mode of the electric field is a versatile tool, with the potential to provide the on-demand generation of single photons or a matter-light interface in a quantum network. This thesis presents the construction and characterisation of an \emph{a priori} deterministic single-photon source using single 87Rb atoms coupled to a high finesse optical cavity. These photons show a high degree of indistinguishability and long coherence times with a two-photon Hong-Ou-Mandel visibility of (70.8±4.6)% over the entire interaction time of 300ns long photons, further increasing to ≥97.8% by post-selecting only detection events within 23ns of each other. No degradation of performance is observed when interfering these pairs through a 4x4 multimode interferometer integrated onto a photonic chip with non-classical correlations measured between photon detections orders of magnitude further separated in time than the propagation time through the chip. The production scheme for polarised single photons is considered in detail. Cavity birefringence is found to alter the polarisation state of the emitted photons and a novel model to incorporate this effect is presented. Further deviations from a simple coupling model are observed in the modified hyperfine atomic structure in the intermediate strength magnetic fields required for polarised photon emission. The behaviour in this regime is modelled and shown to explain previously unresolved observations of the asymmetric production efficiencies of orthogonally polarised photons.

Authors: Barrett, T

• DOI: 10.5287/ora-mnqmg1xnp
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford