Quantum logic detection of collisions between single atom–ion pairs

Studies of interactions between a single pair of atoms in a quantum state are a corner-stone of quantum chemistry, yet the number of demonstrated techniques that enable the observation and control of the outcome of a single collision is still small. Here we demonstrate a technique to study interactions between an ultracold neutral atom and a cold ion using quantum logic. We measure the inelastic release of hyperfine energy in a collision between an ultracold rubidium atom and isotopes of singly ionized strontium that we do not have experimental control over. We detect the collision outcome and measure the inelastic rate of the chemistry ion by reading the motional state of a logic ion qubit in a single shot. Our work extends the toolbox for studying elastic, inelastic and reactive chemical processes with existing experimental tools, especially for atomic and molecular ions for which direct laser cooling and state detection are unavailable.