Interplay between exchange interaction and magnetic field gradient in a double quantum dot with two individual electron spin qubits

We studied experimentally the coherent exchange interaction between two antiparallel electron spins in a double quantum dot with an increasing magnetic field gradient between the two dots. We observed an increase of the oscillation frequency and a reduction of the oscillation contrast. Both observations are consistent with a simple model of two spins interacting via exchange interaction. The demonstrated control of the two-electron spin states is interesting to produce gates for individual spin qubits.