Buffer gas cooling of a trapped ion to the quantum regime

Abstract

Great advances in precision quantum measurement have been achieved with trapped ions and atomic gases at the lowest possible temperatures [1-3]. These successes have inspired ideas to merge the two systems [4]. In this way one can study the unique properties of ionic impurities inside a quantum fluid [5][6][7][8][9][10][11] or explore buffer gas cooling of the trapped ion quantum computer [12]. Remarkably, in spite of its importance, experiments with atom-ion mixtures remained firmly confined to the classical collision regime [13]. We report a collision energy of 1.15(0.23) times the s-wave energy (or 9.9(2.0) µK) for a trapped ytterbium ion in an ultracold lithium gas. We observed a deviation from classical Langevin theory by studying the spin-exchange dynamics, indicating quantum behavior in the atom-ion collisions. Our results open up numerous opportunities, such as the exploration of atom-ion Feshbach resonances [14,15], in analogy to neutral systems [16].

Optical Traps for Sympathetic Cooling of Ions with Ultracold Neutral Atoms

“…Dipole trap lasers operated at optimized detunings and initialization of the ion at sub-Doppler temperatures [10,40] would allow to substantially decrease the optical intensity initially required to trap the Ba + ion, reducing the generation rates of Rb + /Rb + 2 ions. Similarly, using a different element, such as fermionic 6 Li, may allow to precool Ba + to lower energies in the hybrid trap according to theoretical predictions [23] or, as recently demonstrated, for the 6 Li − 171 Yb + system [24]. With the outlined technical improvements, thermal equilibration of Ba + and Rb should be within reach in the current setup.…”

“…More recently, promising strategies for specific scenarios have been developed, requiring e.g. Rydberg atoms and ions [17], extremely large ion-atom mass ratios [21,23,24] or Rydberg excitations within homonuclear atomic ensembles [25]. Yet a universal approach for reaching deep into the quantum regime of interaction for generic combinations of atom and ion species, or even (higher-dimensional) Coulomb crystals, remains an outstanding challenge.…”

Vibrational Quenching of Weakly Bound Cold Molecular Ions Immersed in Their Parent Gas

“…A related study used the ion trap to capture the reaction products of the recombination of three neutral atoms [3]. Recently, cooling of the system down to the s-wave regime where the ion-atom interaction is taking place in a single partial wave has been demonstrated [4]. Furthermore, it has become possible to sympathetically cool ions which are placed in a static optical trap [5], which in principle allows for reaching even lower temperatures.…”

Electro-Optical Ion Trap for Experiments with Atom-Ion Quantum Hybrid Systems

“…A possible solution to reach the quantum regime with RF-trapped ions in an ultracold bath of atoms is to properly choose the atomic species on the basis of their mass ratio, thus limiting the energy transfer from the RF trapping field to the atom-ion system due to the presence of micromotion, and lowering the experimentally attainable temperature [9]. Following this strategy, the group of R. Gerritsma has recently observed atom-ion collisional energies for which only s-and p-waves contribute to the collisions [10]. An alternative strategy to circumvent the detrimental effects of micromotion is to change the ion confinement technique.…”