Using engineered broadband micropillar cavity photon pair source based on quantum dots to study two-photon interference and its dependency on temporal correlation, decoherence, and postselection

Sammanfattning: Entangled photon pairs play a crucial role in quantum information processing such as quantumkey distribution, linear optical quantum computation, quantum teleportation, entanglement swapping, etc. Quantum dots have gathered much attention due to their deterministic generation of the photon pairs. The emission process of the photon pair in a quantum dot relies on the cascaded spontaneous emission of a three-level system. Time correlations between emitted photons arise because of their time-ordered emissions. The time correlations lead to low purities of photonic states, resulting in deteriorated photon indistinguishability. We explore the visibility of the two-photon interference depending on the coherence times. Furthermore, we investigate the photon indistinguishability in the cascade emissions by executing the temporal post-selection from a triggered two-photon interference. Low photon collection efficiency calls for a photonic structure such as a micropillar cavity. The usual technique is to adopt the Purcell enhancement. However, this benchmark is not suitable for biexciton-exciton photon pairs because biexciton and exciton photons have different energies. We developed a new paradigm to increase the collection efficiency based on suppression of the emission into the outside of cavity mode using the low-quality factor cavity, which contradicts the conventional method relying on the Purcell enhancement.