Sign switching of superexchange mediated by a few electrons in a nonuniform magnetic field

Long-range interaction between distant spins is an important building block for the realization of a large quantum-dot network in which couplings pairs can be selectively addressed. Recent experiments on coherent oscillation logical states remote facilitated by intermediate electron were first step large-scale quantum information processing. Reaching this ultimate goal requires extensive studies superexchange different spatial arrangements and configurations. Here, we consider linear triple dot with two antiparallel outer dots forming while varying numbers electrons middle form mediator, facilitates interaction. We show that enhanced when number mediating increases. In addition, four-electron triplet mediator further enhances strength. Our work guide to scale up array controllable dense connectivity.