Investigations of Coherence in Perovskite Quantum Dots with Classical and Quantum Light

Perovskite quantum dots (PQDs) with different compositions have shown promise for applications in light-emitting devices, photovoltaic devices, and quantum optical technologies due to their superior optical and photo-physical properties compared to that of traditional nanoparticles. Here, we report composition dependent exciton coherence time in halide PQDs using time-resolved two-photon near-field scanning optical microscopy (NSOM) at room temperature. When compared to hybrid organic-inorganic PQDs, all-inorganic PQDs have longer electronic coherent dynamics, lasting up to 128 fs, whereas hybrid PQDs have a shorter exciton coherence time of 85 fs at room temperature. We also illustrated how these PQDs interact with entangled (non-classical) light. In this context, we measured the classical two-photon absorption (TPA) and entangled two-photon absorption (ETPA) cross-sections. We combined electronic structure calculations and ETPA measurements to estimate the lifetime in these quantum dot systems to analyze trends in the cross-sections. Comparisons are made between the quantum dots based on both the time-resolved and quantum light measurements. This investigation is useful in understanding the degree of coherence in PQDs analyzed from different measurements. This information will have an impact on the possible use of PQDs for quantum information science.