Fig. 3: Proof of principle experiment with a single ¹³C spin and a single NV center.

a Sensing sequence of the proof of principle experiment. The ¹³C spin is hyperpolarized with the pulse-pol sequence before the nuclear spin precession is initiated with a (π/2)_ref pulse from the reference RF source. The nuclear spin evolves freely during τ_fid (10 μs) and gets rotated to the z-basis with a second (π/2)_ref pulse from the same source. The z-component of the polarization is measured with a Ramsey sequence on the sensor spin ((π/2)_x − (π/2)_y) during τ_sens (15 μs) and the sensor spin is readout with a laser pulse at time T_i. Finally the nuclear spin is rotated back with a (3π/2)_ref pulse, continuing its free evolution. The Rabi period of the applied RF pulses is 66 μs. Inclusion of the repolarization time (2.5 μs), readout time (1.9 μs) and an additional wait time (10 μs) after the RF pulse leads to a sampling time of 105.5 μs. b Experimental measurement of the nuclear evolution under the protocol above at resonance. The experimental time trace (blue) is fitted by an exponentially decaying cosine (orange). For the proof of principle the free evolution of the target spin was implemented as a phase shift in the 3π/2 pulse with Φ = π/2, leading to a normalized signal periodicity of 4 × 105.5 μs. The decay rate of the signal is Γ = 0.6 ± 0.1 kHz. The spectrum of the signal with a peak at 2.368 kHz is shown in c (blue) alongside the Fourier spectrum of the fit (green) and the residuals of the fit (orange) from b.