Robust biexciton preparation for entangled photon-pair generation by single-shot Floquet driving.

Abstract

Quantum emitters driven by resonant two-photon excitation are a leading source for deterministically generated entangled photon pairs, essential for scalable photonic quantum technologies. However, conventional excitation schemes pose various constraints, limiting their scalability and practicability. Here, we demonstrate how biexciton preparation schemes with significantly improved robustness and reduced experimental demands can be identified using a novel design principle: ultrafast single-shot Floquet driving. This is achieved by employing two strongly and symmetrically detuned pulses, whose superposition generates a stroboscopic Hamiltonian that enables direct coupling between ground and biexciton states. Moreover, a pulse delay serves as a tuning knob, introducing an effective magnetic field making biexciton preparation particularly robust. Experimentally, we achieve a biexciton occupation exceeding 96% and preserve photon-pair entanglement with a fidelity of 93.4%. Our work opens avenues for the design of quantum control protocols with superior performance across diverse quantum emitters and qubit platforms.