41 research outputs found
Observation of Interactions between Trapped Ions and Ultracold Rydberg Atoms
We report on the observation of interactions between ultracold Rydberg atoms
and ions in a Paul trap. The rate of observed inelastic collisions, which
manifest themselves as charge transfer between the Rydberg atoms and ions,
exceeds that of Langevin collisions for ground state atoms by about three
orders of magnitude. This indicates a huge increase in interaction strength. We
study the effect of the vacant Paul trap's electric fields on the Rydberg
excitation spectra. To quantitatively describe the exhibited shape of the ion
loss spectra, we need to include the ion-induced Stark shift on the Rydberg
atoms. Furthermore, we demonstrate Rydberg excitation on a dipole-forbidden
transition with the aid of the electric field of a single trapped ion. Our
results confirm that interactions between ultracold atoms and trapped ions can
be controlled by laser coupling to Rydberg states. Adding dynamic Rydberg
dressing may allow for the creation of spin-spin interactions between atoms and
ions, and the elimination of collisional heating due to ionic micromotion in
atom-ion mixtures.Comment: 7 pages, 5 figures, including appendices. Note that the title has
been changed in version
Trapped ions in Rydberg-dressed atomic gases
We theoretically study trapped ions that are immersed in an ultracold gas of
Rydberg-dressed atoms. By off-resonant coupling on a dipole-forbidden
transition, the adiabatic atom-ion potential can be made repulsive. We study
the energy exchange between the atoms and a single trapped ion and find that
Langevin collisions are inhibited in the ultracold regime for these repulsive
interactions. Therefore, the proposed system avoids recently observed ion
heating in hybrid atom-ion systems caused by coupling to the ion's radio
frequency trapping field and retains ultracold temperatures even in the
presence of excess micromotion.Comment: 9 pages, 5 figures including appendice
Observation of collisions between cold Li atoms and Yb ions
We report on the observation of cold collisions between Li atoms and
Yb ions. This combination of species has recently been proposed as the most
suitable for reaching the quantum limit in hybrid atom-ion systems, due to its
large mass ratio. For atoms and ions prepared in the ground state,
the charge transfer and association rate is found to be at least~10 times
smaller than the Langevin collision rate. These results confirm the excellent
prospects of Li--Yb for sympathetic cooling and quantum information
applications. For ions prepared in the excited electronic states ,
and , we find that the reaction rate is dominated by
charge transfer and does not depend on the ionic isotope nor the collision
energy in the range ~1--120~mK. The low charge transfer rate for ground
state collisions is corroborated by theory, but the shell in the Yb
ion prevents an accurate prediction for the charge transfer rate of the
, and states. Using \textit{ab initio}
methods of quantum chemistry we calculate the atom-ion interaction potentials
up to energies of 30~cm, and use these to give qualitative
explanations of the observed rates.Comment: 8 pages, 7 figures (including appendices
Rydberg excitation of a single trapped ion
We demonstrate excitation of a single trapped cold Ca ion to
Rydberg levels by laser radiation in the vacuum-ultraviolet at 122 nm
wavelength. Observed resonances are identified as 3dD to 51 F, 52 F
and 3dD to 64F. We model the lineshape and our results imply a
large state-dependent coupling to the trapping potential. Rydberg ions are of
great interest for future applications in quantum computing and simulation, in
which large dipolar interactions are combined with the superb experimental
control offered by Paul traps.Comment: 4 pages, 3 figure
Prospects of reaching the quantum regime in Li-Yb mixtures
We perform numerical simulations of trapped Yb ions that are
buffer gas cooled by a cold cloud of Li atoms. This species combination has
been suggested to be the most promising for reaching the quantum regime of
interacting atoms and ions in a Paul trap. Treating the atoms and ions
classically, we compute that the collision energy indeed reaches below the
quantum limit for a perfect linear Paul trap. We analyze the effect of
imperfections in the ion trap that cause excess micromotion. We find that the
suppression of excess micromotion required to reach the quantum limit should be
within experimental reach. Indeed, although the requirements are strong, they
are not excessive and lie within reported values in the literature. We analyze
the detection and suppression of excess micromotion in our experimental setup.
Using the obtained experimental parameters in our simulation, we calculate
collision energies that are a factor 2-11 larger than the quantum limit,
indicating that improvements in micromotion detection and compensation are
needed there. We also analyze the buffer-gas cooling of linear and
two-dimensional ion crystals. We find that the energy stored in the eigenmodes
of ion motion may reach 10-100 K after buffer-gas cooling under realistic
experimental circumstances. Interestingly, not all eigenmodes are buffer-gas
cooled to the same energy. Our results show that with modest improvements of
our experiment, studying atom-ion mixtures in the quantum regime is in reach,
allowing for buffer-gas cooling of the trapped ion quantum platform and to
study the occurrence of atom-ion Feshbach resonances.Comment: 39 pages, 22 figure