Solid-state electronic spin coherence time approaching one second

TL;DR

This paper reports a breakthrough in extending the coherence time of NV center spins in diamond to nearly one second at 77 K, enabling advanced quantum applications by employing dynamical decoupling techniques.

Contribution

Demonstrated over two orders of magnitude improvement in NV spin coherence time using dynamical decoupling, approaching the fundamental $T_1$ limit across temperatures.

Findings

$T_2$ reaches approximately 0.5 seconds at 77 K.

$T_2$ is limited by phonon-induced decoherence, about half of $T_1$.

Results are applicable to ensembles and do not depend on specific NV selection.

Abstract

Solid-state electronic spin systems such as nitrogen-vacancy (NV) color centers in diamond are promising for applications of quantum information, sensing, and metrology. However, a key challenge for such solid-state systems is to realize a spin coherence time that is much longer than the time for quantum spin manipulation protocols. Here we demonstrate an improvement of more than two orders of magnitude in the spin coherence time ($T_2$) of NV centers compared to previous measurements: $T_2 \approx 0.5$ s at 77 K, which enables $\sim 10^7$ coherent NV spin manipulations before decoherence. We employed dynamical decoupling pulse sequences to suppress NV spin decoherence due to magnetic noise, and found that $T_2$ is limited to approximately half of the longitudinal spin relaxation time ($T_1$) over a wide range of temperatures, which we attribute to phonon-induced decoherence. Our results apply to ensembles of NV spins and do not depend on the optimal choice of a specific NV, which could advance quantum sensing, enable squeezing and many-body entanglement in solid-state spin ensembles, and open a path to simulating a wide range of driven, interaction-dominated quantum many-body Hamiltonians.