Floquet Prethermalization with Lifetime Exceeding 90 s in a Bulk Hyperpolarized Solid

We report the observation of long-lived Floquet prethermal states in a bulk solid composed of dipolar-coupled ¹³C

nuclei in diamond at room temperature. For precessing nuclear spins prepared in an initial transverse

state, we demonstrate Floquet control that prevents their decay over multiple-minute long periods. We observe

Floquet prethermal lifetimes T₂'≈90.9s, extended >60,000-fold over the nuclear free induction decay times. The

spins themselves are continuously interrogated for ∼10min, corresponding to the application of ≈5.8M control

pulses. The ¹³C nuclei are optically hyperpolarized by lattice Nitrogen-Vacancy (NV) centers; the combination

of hyperpolarization and continuous spin readout yields significant signal-to-noise in the measurements. This

allows probing the Floquet thermalization dynamics with unprecedented clarity. We identify four characteristic

regimes of the thermalization process, discerning short-time transient processes leading to the prethermal

plateau, and long-time system heating towards infinite temperature. This work points to new opportunities

possible via Floquet control in networks of dilute, randomly distributed, low-sensitivity nuclei. In particular, the

combination of minutes-long prethermal lifetimes and continuous spin interrogation opens avenues for quantum

sensors constructed from hyperpolarized Floquet prethermal nuclei.