Figure 5.

Experimental setup and magnetometry with repetitive readout [78]. Image reprinted with permission from [78], copyright 2016 AAAS. (A) Experimental setup. NV center electronic spin and its associated 15 N nuclear spin are used as a proximal quantum sensor to probe ubiquitin proteins on the surface of the diamond. (B) Quantum circuit diagram and experimental magnetometry pulse sequence. (C) Repetitive readout cycles and measured fidelity gain. MW – microwave; RF – radiofrequency; APD – avalanche photodiode; B – nuclear spin magnetic field.