(color online) Controlling the strength of quantum measurements by DD and single-shot readout of a weakly coupled nuclear spin. (a) The accumulated phase of the center electron spin (and thus the measurement strength of the weakly coupled target nuclear spin) is controlled by the pulse number of the applied CPMG sequence. (b) Pulse sequence. The weakly coupled nuclear spin is selectively addressed and its state is mapped to the center electron spin by the CPMG sequence, and then readout by the subsequent projective measurement on the NV electron spin. (c) Typical quantum jump signal of a weakly coupled nuclear spin under an external magnetic field of 691 Gs. Each data point is the sum of trails of the sequence in panel (b). Reproduced from Ref. [29], APS.