Precession during pulses By considering a system in which the two spins are exactly on resonance with the applied pulses, equivalent to a single molecule, the Zeeman terms in the static Hamiltonian go to zero and only the inter-spin coupling term is active. In this case the fidelity of the simulated entangling gate oscillates with frequency 𝜔 )* as the inter-pulse delay is incremented (Figure ). The maxima in fidelity occur at 𝜏 ≈ (2A0"):