Spontaneous Parametric Down-Conversion (SPDC) is a nonlinear optical process where a high-energy photon splits into a pair of lower-energy entangled photons. This phenomenon is fundamental to quantum optics and quantum information science, enabling the generation of entangled photon pairs for secure communication and quantum computing. By studying materials that exhibit strong exciton-biexciton interactions, we investigate alternative approaches to correlated photon pair generation beyond traditional nonlinear crystals.
Our work with CdS/CdSe/CdS quantum shells demonstrates exciton-biexciton cascaded emission, a process analogous to SPDC, where a biexciton decays into two photons with distinct spectral separation (~75–80 meV). The observed photon bunching behavior confirms strong correlations between emitted photons, a key characteristic in entangled photon pair generation. Theoretical modeling using a three-level quantum system allows us to analyze photon statistics and emission dynamics, further validating the potential of quantum shells for quantum optical applications. (ACS Nano 2024, 18, 44, 30863–30870)
(a) Schematics of radiative XX−X cascade and spectrally resolved correlation measurements.
By leveraging the unique optical properties of these nanostructures, we aim to develop stable and efficient sources of correlated photon pairs. This research expands the possibilities for integrated quantum photonics, offering new pathways for scalable and tunable entangled photon generation in nanoscale systems.