Floquet prethermalization with lifetime exceeding 90s in a bulk\n hyperpolarized solid

Abstract

We report the observation of long-lived Floquet prethermal states in a bulk\nsolid composed of dipolar-coupled $^{13}$C nuclei in diamond at room\ntemperature. For precessing nuclear spins prepared in an initial transverse\nstate, we demonstrate pulsed spin-lock Floquet control that prevents their\ndecay over multiple-minute long periods. We observe Floquet prethermal\nlifetimes $T_2'\\approx$90.9s, extended >60,000-fold over the nuclear free\ninduction decay times. The spins themselves are continuously interrogated for\n$\\sim$10min, corresponding to the application of $\\approx$5.8M control pulses.\nThe $^{13}$C nuclei are optically hyperpolarized by lattice Nitrogen Vacancy\n(NV) centers; the combination of hyperpolarization and continuous spin readout\nyields significant signal-to-noise in the measurements. This allows probing the\nFloquet thermalization dynamics with unprecedented clarity. We identify four\ncharacteristic regimes of the thermalization process, discerning short-time\ntransient processes leading to the prethermal plateau, and long-time system\nheating towards infinite temperature. This work points to new opportunities\npossible via Floquet control in networks of dilute, randomly distributed,\nlow-sensitivity nuclei. In particular, the combination of minutes-long\nprethermal lifetimes and continuous spin interrogation opens avenues for\nquantum sensors constructed from hyperpolarized Floquet prethermal nuclei.\n