Figure 1. System and methods for measuring NV centre spin decoherence in a ¹³C nuclear spin bath in diamond.

(a) Atomic structure of a nitrogen (N) - vacancy (V) centre in diamond and the magnetic field B. (b) Pulse sequences for the optically detected magnetic resonance measurement. The centre spin is initialized by the 532-nm laser pulse, manipulated by microwave pulses, and read out through the fluorescence. (c) Energy levels of an NV centre spin. The electron spin and ¹⁴N-nuclear spin states are denoted by |m_s〉 and |m_I〉_14N for m_s,m_I=0,±, respectively. The level splitting is caused by the hyperfine coupling to the ¹⁴N nuclear spin. The single-transition coherence L_0,+ and the double-transition coherence L_+,− are measured in the experiments. The solid (dashed) vertical arrows denote the nonselective (selective) microwave excitations of the centre spin. (d) Schematic of a ¹³C-nuclear spin bath (enclosed by the circle), which together with the NV centre spin form a relatively closed quantum system.