Magnetic Field Control of Exchange and Noise Immunity in Double Quantum Dots

We employ density functional calculated eigenstates as a basis for exact diagonalization studies of semiconductor double quantum dots, with two electrons, through the transition from the symmetric bias regime to the regime where both electrons occupy the same dot. We calculate the singlet-triplet splitting $J(\epsilon)$ as a function of bias detuning $\epsilon$ and explain its functional shape with a simple, double anti-crossing model. A voltage noise suppression "sweet spot," where $dJ(\epsilon)/d\epsilon=0$ with nonzero $J(\epsilon)$, is predicted and shown to be tunable with a magnetic field $B$.