Optically Hyperpolarized Materials for Levitated Optomechanics

Quantum 9, 1928 (2025).

https://doi.org/10.22331/q-2025-12-03-1928

We explore the potential of levitating solids embedded with non-permanent, optically controllable electron spins, which can be used to hyperpolarize their nuclear spin environment with exceptionally long lifetimes. For example, pentacene-doped naphthalene, which will also serve as our prime example, can achieve bulk polarization exceeding $80,%$ at cryogenic temperatures with polarization lifetimes extending over weeks. These materials make a compelling case for applications such as matter-wave interferometry and novel uses of established NMR techniques. In that spirit, we design a multi-spin Stern-Gerlach-type interferometry protocol which, thanks to the homogeneous spin distribution and the absence of a preferential nuclear-spin quantization axis in such materials, avoids many of the limitations associated with solid state crystals hosting electronic spin defects, such as nanodiamonds containing NV centers. We assess the potential of our interferometer to enhance existing bounds on the free parameters of objective collapse models. Beyond matter-wave interferometry, we analyze the prospects for implementing magic angle spinning at frequencies surpassing the current standard in NMR, capitalizing on the exceptional rotational capabilities offered by levitation. Additionally, we outline a novel protocol for measuring spin ensemble polarization via the position of the nanoparticle and conduct an analysis of dominant noise sources, benchmarking the required isolation levels for various applications.