  We present electron spin entanglers--devices creating mobile spin-entangled
electrons that are spatially separated--where the spin-entanglement in a
superconductor present in form of Cooper pairs and in a single quantum dot with
a spin singlet groundstate is transported to two spatially separated leads by
means of a correlated two-particle tunneling event. The unwanted process of
both electrons tunneling into the same lead is suppressed by strong Coulomb
blockade effects caused by quantum dots, Luttinger liquid effects or by
resistive outgoing leads. In this review we give a transparent description of
the different setups, including discussions of the feasibility of the
subsequent detection of spin-entanglement via charge noise measurements.
Finally, we show that quantum dots in the spin filter regime can be used to
perform Bell-type measurements that only require the measurement of zero
frequency charge noise correlators.
