Fig. 3: Three-spin AQT.

a Quantum circuit diagram for the experiment. The spin chain is initialized as \(\left|{S}_{12}{\downarrow }_{3}{\uparrow }_{4}\right\rangle\) and the AQT implemented in spins 1–3 transfers the state of spin 3 to spin 1 and the singlet state in spins 1–2 to spins 2–3. Then, spins 3–4 and 2–3 are swapped, in this order. We then measure the left pair \(({P}_{\,\text{S}}^{\text{L}\,})\) and the right pair \(({P}_{\,\text{S}}^{\text{R}\,})\) in the singlet/triplet basis via Pauli spin blockade. The colors represent the physical locations of the initial states. b Change in exchange-coupling strengths between qubits for the AQT step in (a). Here, T is the Hamiltonian interpolation time and 0 < t < T. c Singlet-return probabilities of the left and right pairs as a function of interpolation time T for f = +1. d Same as (c), but for f = −1. In both (c) and (d), the expected outcomes under ideal conditions (dotted lines) as well as simulated results including known errors and noise (dashed lines) are overlaid on top of the measured data (solid lines). The insets in (c) and (d) show exchange oscillations in spins 1–2 and S − T⁰ oscillations in spins 3–4 after the experiment described in (a). “Gate time” refers to these oscillation times. The presence of exchange oscillations in spins 1–2 and S − T⁰ oscillations in spins 3–4 provides evidence of the successful adiabatic transfer. Each data point represents the average of 512 single-shot measurements.