Entangling gates for local spin qubits by using electric current

We show that entanglement between two local spins which are initially independent and act as qubits can be established by applying an electron current through them. The setup can be realized by using spin-(1/2) quantum dots as the qubits and equally connecting them to leads with the tip of scanning tunnel microscopy. The tunneling of electrons through two dots is in the sequential regime and the entanglement between dots originates from the quantum coherence of two tunneling channels. We calculate the effect of the electron current on the entanglement of local qubits fully quantum-mechanically by using extended scattering-matrix theory and analyze the favorite conditions for the realization of entangling gates.