Temperature-dependent coherence properties of NV ensemble in diamond up to 600 K

The nitrogen-vacancy (NV) center in diamond is an ideal candidate for quantum sensing because of its excellent spin coherence property as well as the possibility for optical initialization and readout. Previous studies, on the other hand, have typically been conducted at low or room temperature. The inability to fully understand the coherence properties of the NV center at high temperatures limits NV's further applications. We systematically investigate the coherence properties of NV center ensemble at temperatures ranging from 300 K to 600 K in this paper. Coherence time ${T}_{2}$ decreases rapidly from $184\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\text{s}$ at 300 K to $30\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\text{s}$ at 600 K due to the interaction with paramagnetic impurities. At all experiment temperatures, both single-quantum and double-quantum transitions exhibit a ${T}^{5}$ relaxation rate, which is attributed to the two-phonon Raman process. Nonetheless, the inhomogeneous dephasing time ${T}_{2}^{*}$ and thermal-echo decoherence time ${T}_{\text{TE}}$ remain almost unchanged at temperature up to 600 K. A thermal-echo-based thermometer is demonstrated to have a sensitivity of $41\phantom{\rule{4pt}{0ex}}\text{mK}/\sqrt{\mathrm{Hz}}$ at 450 K. These findings will pave the way for NV-based high-temperature sensing and provide a more comprehensive understanding of solid-state qubit decoherence.