Fig. 6: Entanglement between two P1s.

a Experimental sequence to measure coupling and generate entanglement between S1 and S2. DEER measurements initialize the JT axis and nitrogen state of S1 and S2 (K = 820, 50, and f = f_+1D, f_+1A), followed by DEER(y) measurements to initialize their electron spin states (L = 6, 3). Two π/2 pulses and an evolution for time 2t under a double echo implements the S_zS_z interaction with both spins in the equatorial plane of the Bloch sphere. This is followed by single-qubit gates (dashed boxes) for full two-qubit state tomography and two final DEER(y) measurements for electron spin readout. We apply an additional initial sequence (K = 5, f_+1A) to speed up the experiment (not shown in sequence, see Supplementary Note 15). b The coherent oscillation of 〈XZ〉 as a function of interaction time 2t demonstrates a dipolar coupling J = −2π ⋅ 17.8(5) kHz between S1 and S2. c Density matrix of the S1 and S2 electron spins after applying the sequence as shown in a for 2t = π/J. The fidelity with the target state is F = 0.81(5). Transparent bars indicate the density matrix for the target state \(\left|{{\Psi }}\right\rangle\). All error bars indicate one statistical standard deviation.