Fig. 3.

(A and B) Pulse sequence used to observe S-T₀ oscillations when J > h. We initialize into the S(1, 1) state by preparing the S(0, 2) ground state at point M and ramping adiabatically through the (0, 2)–(1, 1)S anticrossing to an intermediate point N and then to P, where the singlet and triplet states are no longer energy eigenstates. Decreasing ε suddenly brings the state nonadiabatically to a value of the detuning where J is comparable or greater than h, inducing coherent rotations. The Bloch vector rotates around the new axis for a time τ_s. Reversing the sequence of ramps projects the state into S(0, 2) for readout. (C) Probability P_S of observing the singlet as a function of the detuning voltage of the exchange pulse $V_{\epsilon }^{\text{ex}}$ and pulse duration τ_s with the measurement point M fixed in the (0, 2) charge state. (D) P_S as a function of τ_s, extracted from the data in C at three different values of $V_{\epsilon }^{\text{ex}}$. Each trace is offset by 0.7 for clarity. Solid curves are fits to the product of a cosine and a Gaussian (30), with amplitude, frequency, phase, and decay time as free parameters. (E) Bloch spheres showing rotations around the axes corresponding to each trace in D. The angle θ between the rotation axis and the z axis is labeled for each case.