(A) Different ways to prepare an electron spin center in carbon materials. (B) Electron spin multiplicity and coherence time achieved with different types of carbon-based spin materials. (C) Schematic illustration of the quantum state of spin controlled by microwave pulses. (D) Instrument setups of EPR and (E) ODMR used to apply the spin manipulation and readout. (F) Ultra-sensitive quantum sensor for temperature detection. Reproduced with the permission of ref. [4]. (G) Solid-state atomic clock transitions for frequency standard. Reproduced with the permission of ref. [6]. (H) Addressable multi-level transitions to implement geomatic phase gate. Reproduced with the permission of ref. [3]. (I) Single quantum system experiment to manifest the break of parity-time symmetry with the r>1 region. Reproduced with the permission of ref. [7].