Selective Biexciton Generation under Energy-Time Entangled Quantum Light in Quantum Dots

Quantum light provides opportunities for controlling multiphoton absorption beyond the classical limits. Here, we investigate biexciton generation in nanocrystal quantum dots driven by energy-time-entangled photon pairs generated via spontaneous parametric downconversion. We show that frequency–time correlations between pairs of photons increase the population of biexcitons over excitons, thereby lending specificity to the excitation of many-body states. By employing a three-level model, we demonstrate that biexciton generation depends nontrivially on the photon entanglement time and pump bandwidth. We find that maximizing efficiency requires an optimally shaped entangled photon field rather than simply scaling parameters for a monotonic improvement. Extending to a realistic CdSe/CdS core–shell quantum dot containing many excitonic states coupled to the quantum field, we demonstrate that increasing the biphoton arrival-time entanglement (closer arrival time) enhances constructive pathway interference and expands accessible excitation channels while preserving better energy-conservation in excitation than classical light when generating biexcitons. Furthermore, tuning the time-correlation properties enables selective excitation of closely spaced biexciton states. These results establish entangled photons as tools for selective excitation and control of higher-order excited states in quantum-confined systems.