NAnoparticle Fountain for TIp-based Nonlinear Interaction

Objective

Quantum mechanics has been verified with high precision in atomic and molecular systems, yet its extension to macroscopic objects remains unresolved and poses major conceptual and experimental challenges. Levitated nanoparticles are uniquely suited to address this gap owing to their large mass and coherence length. Progress is limited by two challenges: (i) expanding nanoparticle wavefunctions to nanometre scales without decoherence, and (ii) coupling these expanded states to a structured potential with matching spatial nonlinearity, so that non-Gaussian features can be created, measured, and analysed. State-of-the-art optical control faces a fundamental trade-off: strong optical gradients are diffraction-limited and introduce decoherence through photon recoil. NAFTINI (NAnoparticle Fountain for TIp-based Nonlinear Interaction) addresses these challenges by combining neutral, optically prepared nanoparticles with electrostatically engineered, nanosharp tips positioned at the apex of a free-flight fountain trajectory. A dielectric nanoparticle is trapped and cooled in an optical tweezer, neutralised, launched upward by dynamically shifting the potential, and recaptured after a controlled free evolution of a few milliseconds. At the apex, where the quantum wavefunction is maximally expanded and the particle is outside the optical focus, it traverses the near field of a biased nanotip whose curvature defines the spatial scale of the nonlinearity. The architecture will be calibrated against decoherence sources and enables light-free, nanometre-scale manipulation with attonewton forces, while preserving the isolation of a neutral polarisable particle outside the immediate tip region where gradients are high. This way, NAFTINI will provide a reproducible platform for probing quantum behaviour of mesoscopic objects.