While a fidelity can be determined for each pair of operations acting on any arbitrary quantum state, here we limit ourselves to those states which we expect to be converted into 𝑆 0 & and 2𝑆 0 % 𝐼 0 ' coherences, and thus yield oscillatory components in the real parts of the DEERATom traces detected at 𝜈 ) (Table ). Experimentally the filter pulses were applied at a time such that their centre corresponded to the maximum echo intensity, and we mimic this in our simulations. The fidelity of the operations is determined by comparing the quantum state at time 2𝜏 0 to the expected coherence. For the 'single molecule' model system, in which both spins are directly on resonance with the applied pulses, the simulated fidelity decreases uniformly as the pulse length is increased. For 1 ns pulses the fidelity of all pairs of operations is 1.0000, but this drops to between 0.9788 and 0.9882 for a pulse length of 80 ns (Figure ). There is no discernible pattern between the pairs of operations and their sensitivity to pulse length.