Extended Data Fig. 2: Voltage dependence of the exchange interaction, J(ϵ).
a, Pulse sequence used to measure the exchange oscillations in b (left panel) and schematic of the relevant energy levels (right panel). After initializing the system in the (4,0) singlet ground state, we prepare the superposition state (\(\left\vert {S}^{+-}\right\rangle +i\left\vert {T}_{0}^{+-}\right\rangle\))\(\sqrt{2}\) via a 3π/2 pulse around ΔEZ at ϵ=19 mV. The state evolves at different values of ϵ (therefore under different values of J) for a variable time te. After the evolution, we use a π/2 pulse around ΔEZ to map this superposition state to \(\left\vert {S}^{+-}\right\rangle\) and measure the singlet return probability PS. b, Measurement of exchange oscillations between superpositions of \(\left\vert {S}^{+-}\right\rangle\) and \(\left\vert {T}_{0}^{+-}\right\rangle\) at different values of ϵ with Bz = 350 mT. Inset: Absolute value of the fast Fourier transform of the data. c, Values of J as a function of ϵ extracted from the exchange oscillation measurement in b (blue circles) and the spin funnel measurement (red dots). The J values are displayed on a logarithmic scale. The solid line is an empirical fit of the data.
