  We propose an entanglement mechanism of nuclear spins in quantum dots driven
by the electric current. The current accompanied by the spin flip in quantum
dots gradually increases components of larger total spin of nuclei. This
entangled state drastically enhances the spin relaxation rate of electrons,
which can be detected by measuring a leakage current in the spin-blockade
region. This mechanism is not relevant in optical experiments which examine the
spin relaxation of single excitations.
