Phase Locking between Different Partial Waves in Atom-Ion Spin-Exchange Collisions.

We present a joint experimental and theoretical study of spin dynamics of a single ^{88}Sr^{+} ion colliding with an ultracold cloud of Rb atoms in various hyperfine states. While spin exchange between the two species occurs after 9.1(6) Langevin collisions on average, spin relaxation of the Sr^{+} ion Zeeman qubit occurs after 48(7) Langevin collisions, which is significantly slower than in previously studied systems due to a small second-order spin-orbit coupling.

Direct Observation of Atom-Ion Nonequilibrium Sympathetic Cooling.

Sympathetic cooling is the process of energy exchange between a system and a colder bath. We investigate this fundamental process in an atom-ion experiment where the system is composed of a single ion trapped in a radio-frequency Paul trap and prepared in a classical oscillatory motion with total energy of ∼200  K, and the bath is an ultracold cloud of atoms at μK temperature. We directly observe the sympathetic cooling dynamics with single-shot energy measurements during one to several collisions in two distinct regimes.

Publisher Correction: Spin-controlled atom-ion chemistry.

The original version of this Article contained an error in the third sentence of the first paragraph of the 'Spin polarizing the Sr ion with ultracold atoms' section of the Results, which incorrectly read 'The Langevin collision rate is 1.' The correct version adds 'kHz' after '1.' The fifth sentence of this same paragraph originally read as "Although Rb has a I = 3/2 nuclear spin and a hyperfine-split ground-state manifold, Sr has no nuclear spin and a Zeeman split two-fold ground state", which is incorrect.

Spin-controlled atom-ion chemistry.

Quantum control of chemical reactions is an important goal in chemistry and physics. Ultracold chemical reactions are often controlled by preparing the reactants in specific quantum states. Here we demonstrate spin-controlled atom-ion inelastic (spin-exchange) processes and chemical (charge-exchange) reactions in an ultracold Rb-Sr mixture.

Dynamics of a Ground-State Cooled Ion Colliding with Ultracold Atoms.

Ultracold atom-ion mixtures are gaining increasing interest due to their potential applications in ultracold and state-controlled chemistry, quantum computing, and many-body physics. Here, we studied the dynamics of a single ground-state cooled ion during few, to many, Langevin (spiraling) collisions with ultracold atoms. We measured the ion's energy distribution and observed a clear deviation from the Maxwell-Boltzmann distribution, characterized by an exponential tail, to a power-law distribution best described by a Tsallis function.