Entanglement of two individual neutral atoms using Rydberg blockade

We report the generation of entanglement between two individual ${}^{87}$Rb atoms in hyperfine ground states $\mathrm{\mid }F=1,M=1>$ and $\mathrm{\mid }F=2,M=2>$ which are held in two optical tweezers separated by 4 $\mu$m. Our scheme relies on the Rydberg blockade effect which prevents the simultaneous excitation of the two atoms to a Rydberg state. The entangled state is generated in about 200 ns using pulsed two-photon excitation. We quantify the entanglement by applying global Raman rotations on both atoms. We measure that 61% of the initial pairs of atoms are still present at the end of the entangling sequence. These pairs are in the target entangled state with a fidelity of 0.75.