255 research outputs found
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
Resonant tunneling in Y(Dy)Ba2Cu3O7−δ/PrBa2Cu3−xGaxO7−δ/Y(Dy)Ba2Cu3O7−δ ramp-type Josephson junctions
We have investigated both experimentally and theoretically the normal state resistance and Josephson critical current of ramp-type Josephson junctions having YBCO (DyBCO) electrodes and 8–30 nm thick Ga-doped barriers PrBa2Cu3−xGaxO7−δ with Ga content x = 0, 0.05 and 0.1. Analysis of the data shows that the behavior of the junctions can be well described by the model assuming transport through a finite number of localized states in the barrier
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
Quantum Simulation of Quantum Field Theories in Trapped Ions
We propose the quantum simulation of a fermion and an antifermion field modes
interacting via a bosonic field mode, and present a possible implementation
with two trapped ions. This quantum platform allows for the scalable add-up of
bosonic and fermionic modes, and represents an avenue towards quantum
simulations of quantum field theories in perturbative and nonperturbative
regimes.Comment: To be published in Physical Review Letter
Phonon-mediated spin-spin interactions between trapped Rydberg atoms
We theoretically investigate the possibility of creating phonon-mediated
spin-spin interactions between neutral atoms trapped in optical tweezers. By
laser coupling the atoms to Rydberg states, collective modes of motion appear.
We show that these can be used to mediate effective spin-spin interactions or
quantum logic gates between the atoms in analogy to schemes employed in trapped
ions. In particular, we employ Rydberg dressing in a novel scheme to induce the
needed interaction, and we show that it is possible to replicate the working of
the M{\o}lmer-S{\o}rensen entanglement scheme. The M{\o}lmer-S{\o}rensen gate
is widely used in emerging quantum computers using trapped ion qubits and
currently features some of the highest fidelities of any quantum gate under
consideration. We find arbitrarily high fidelity for the coherent time
evolution of the two-atom state even at non-zero temperature.Comment: 6 pages, 3 figure
On Nonlinear Bosonic Coherent States
Nonlinear coherent states are an interesting resource for quantum
technologies. Here we investigate some critical features of the single-boson
nonlinear coherent states, which are theoretically constructed as eigenstates
of the annihilation operator and experimentally realized as stationary states
of a trapped laser-driven ion. We show that the coherence and the
minimum-uncertainty properties of such states are broken for values of the
Lamb-Dicke parameter corresponding to the roots of the Laguerre polynomials,
which enter their explicit expression. The case of the multiboson nonlinear
coherent states is also discussed.Comment: published versio
- …