262 research outputs found
Quantum dynamics of an atomic double-well system interacting with a trapped ion
We theoretically analyze the dynamics of an atomic double-well system with a
single ion trapped in its center. We find that the atomic tunnelling rate
between the wells depends both on the spin of the ion via the short-range
spin-dependent atom-ion scattering length and on its motional state with
tunnelling rates reaching hundreds of Hz. A protocol is presented that could
transport an atom from one well to the other depending on the motional (Fock)
state of the ion within a few ms. This phonon-atom coupling is of interest for
creating atom-ion entangled states and may form a building block in
constructing a hybrid atom-ion quantum simulator. We also analyze the effect of
imperfect ground state cooling of the ion and the role of micromotion when the
ion is trapped in a Paul trap. Due to the strong non-linearities in the
atom-ion interaction, the micromotion can cause couplings to high energy
atom-ion scattering states, preventing accurate state preparation and
complicating the double-well dynamics. We conclude that the effects of
micromotion can be reduced by choosing ion/atom combinations with a large mass
ratio and by choosing large inter-well distances. The proposed double-well
system may be realised in an experiment by combining either optical traps or
magnetic microtraps for atoms with ion trapping technology.Comment: 14 pages, 13 figure
Spectroscopy of the ^2S_{1/2} \rightarrow\,^2P_{3/2} transition in Yb II: Isotope shifts, hyperfine splitting and branching ratios
We report on spectroscopic results on the ^2S_{1/2} \rightarrow\,^2P_{3/2}
transition in single trapped Yb ions. We measure the isotope shifts for all
stable Yb isotopes except Yb, as well as the hyperfine
splitting of the state in Yb. Our results are in
agreement with previous measurements but are a factor of 5-9 more precise. For
the hyperfine constant MHz our results
also agree with previous measurements but deviate significantly from
theoretical predictions. We present experimental results on the branching
ratios for the decay of the state. We find branching fractions for
the decay to the state and state of 0.17(1)% and
1.08(5)%, respectively, in rough agreement with theoretical predictions.
Furthermore, we measured the isotope shifts of the ^2F_{7/2}
\rightarrow\,^1D\left[5/2\right]_{5/2} transition and determine the hyperfine
structure constant for the state in Yb
to be MHz.Comment: 6 pages, 4 figure
Operation of a Microfabricated Planar Ion-Trap for Studies of a Yb-Rb Hybrid Quantum System
In order to study interactions of atomic ions with ultracold neutral atoms,
it is important to have sub-m control over positioning ion crystals.
Serving for this purpose, we introduce a microfabricated planar ion trap
featuring 21 DC electrodes. The ion trap is controlled by a home-made FPGA
voltage source providing independently variable voltages to each of the DC
electrodes. To assure stable positioning of ion crystals with respect to
trapped neutral atoms, we integrate into the overall design a compact mirror
magneto optical chip trap (mMOT) for cooling and confining neutral Rb
atoms. The trapped atoms will be transferred into an also integrated chipbased
Ioffe-Pritchard trap potential formed by a Z-shaped wire and an external bias
magnetic field.We introduce the hybrid atom-ion chip, the microfabricated
planar ion trap and use trapped ion crystals to determine ion lifetimes, trap
frequencies, positioning ions and the accuracy of the compensation of
micromotion.Comment: 10 pages, 13 figure
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
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
Dynamics of a single ion spin impurity in a spin-polarized atomic bath
We report on observations of spin dynamics in single Yb ions immersed in
a cold cloud of spin-polarized Li atoms. This species combination has been
proposed to be the most suitable system to reach the quantum regime in atom-ion
experiments. For Yb, we find that the atomic bath polarizes the
spin of the ion by 93(4)\,\% after a few Langevin collisions, pointing to
strong spin-exchange rates. For the hyperfine ground states of Yb,
we also find strong rates towards spin polarization. However, relaxation
towards the ground state occurs after 7.7(1.5) Langevin collisions. We
investigate spin impurity atoms as possible source of apparent spin-relaxation
leading us to interpret the observed spin-relaxation rates as an upper limit.
Using ab initio electronic structure and quantum scattering calculations, we
explain the observed rates and analyze their implications for the possible
observation of Feshbach resonances between atoms and ions once the quantum
regime is reached.Comment: 10 pages, 11 figure
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