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

Abstract

We report the observation of long-lived Floquet prethermal states in a bulk solid composed of dipolar-coupled 13 C 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 𝑇 2 ≈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 13 C 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.

Electron-to-nuclear spectral mapping via "Galton board" dynamic nuclear polarization

“…These factors can be considerably improved with advancements to the experimental apparatus (see Ref. [16]); we estimate a sensitivity improvement by four orders of magnitude is feasible. Fig.…”

“…Solid red line denotes the resulting NV electronic spectrum g. Starting with optically initialized populations at 𝑚 𝑠 =0 (black balls), chirped microwaves (MWs) [14,15] (curly purple line) drive transitions to the 𝑚 𝑠 =+1 manifold in the Δ 𝑓 window (purple). (C) Experimental protocol consists of DNP applied in narrow Δ 𝑓 windows (left) and interrogating the 13 C nuclei by spinlocked readout [16] (right), here at 7T, employing ∼100k pulses. (D) Single shot NMR spectrum from a representative Δ 𝑓 =10MHz window.…”

“…Inset (i): time-domain 13 C signal under spin-lock control (red) and free induction decay (blue). For the former, we estimate a rotating frame lifetime 𝑇 2 ≈2s [16]. Inset (ii): noise measured in the NMR spectral wing; we estimate a single-shot SNR ≈1.25×10 4 .…”

“…We employ a pulsed spin-locking protocol [22,23] (right panel of Fig. 1C) that allows the 13 C populations to be continuously interrogated for long periods up to the limit set by the rotating-frame lifetimes, typically 𝑇 2 >2s [16]. It consists of a train of 𝜗-pulses spin-locked with the initial 13 C spin state (Fig.…”

“…1C); typical experiments involve >100k pulses. This yields a 13 C readout SNR that is boosted by 10−10 3 times [16] with respect to traditional free induction decay (FID) measurements. Fig.…”