Fiber-Optic Quantum Thermometry with Germanium--Vacancy Centers in Diamond

Accurate, high spatial resolution thermal measurements have provided fundamental insights into many fields of study; however, existing thermometer technology often suffers from one or more limitations, such as low spatial resolution, low accuracy, slow response time, or reliance on cumbersome equipment and invasive measurement techniques. In this work, the development of a highly accurate fiber-optic microthermometer employing exclusively optical interrogation of germanium-vacancy quantum emitters in diamond is presented. This thermometer possesses a thermal resolution of approximately 20 mK/root Hz and a spatial resolution of 25 mu m.