580 research outputs found
Structural transitions of ion strings in quantum potentials
We analyse the stability and dynamics of an ion chain confined inside a
high-finesse optical resonator. When the dipolar transition of the ions
strongly couples to one cavity mode, the mechanical effects of light modify the
chain properties close to a structural transition. We focus on the linear chain
close to the zigzag instability and show that linear and zigzag arrays are
bistable for certain strengths of the laser pumping the cavity. For these
regimes the chain is cooled into one of the configurations by cavity-enhanced
photon scattering. The excitations of these structures mix photonic and
vibrational fluctuations, which can be entangled at steady state. These
features are signalled by Fano-like resonances in the spectrum of light at the
cavity output.Comment: 5 pages, 3 figs - version to appear in PR
Cooling the motion of a trapped atom with a cavity field
We theoretically analyze the cooling dynamics of an atom which is tightly
trapped inside a high-finesse optical resonator. Cooling is achieved by
suitably tailored scattering processes, in which the atomic dipole transition
either scatters a cavity photon into the electromagnetic field external to the
resonator, or performs a stimulated emission into the cavity mode, which then
dissipates via the cavity mirrors. We identify the parameter regimes in which
the atom center-of-mass motion can be cooled into the ground state of the
external trap. We predict, in particular, that for high cooperativities
interference effects mediated by the atomic transition may lead to higher
efficiencies. The dynamics is compared with the cooling dynamics of a trapped
atom inside a resonator studied in [Phys. Rev. Lett. 95, 143001, (2005)] where
the atom, instead of the cavity, is driven by a laser field
Cooling trapped atoms in optical resonators
We derive an equation for the cooling dynamics of the quantum motion of an
atom trapped by an external potential inside an optical resonator. This
equation has broad validity and allows us to identify novel regimes where the
motion can be efficiently cooled to the potential ground state. Our result
shows that the motion is critically affected by quantum correlations induced by
the mechanical coupling with the resonator, which may lead to selective
suppression of certain transitions for the appropriate parameters regimes,
thereby increasing the cooling efficiency.Comment: 4 pages, 3 figures; version published in PR
Ground State Laser Cooling Beyond the Lamb-Dicke Limit
We propose a laser cooling scheme that allows to cool a single atom confined
in a harmonic potential to the trap ground state . The scheme assumes
strong confinement, where the oscillation frequency in the trap is larger than
the effective spontaneous decay width, but is not restricted to the Lamb-Dicke
limit, i.e. the size of the trap ground state can be larger than the optical
wavelength. This cooling scheme may be useful in the context of quantum
computations with ions and Bose-Einstein condensation.Comment: 6 pages, 4 figures, to appear in Europhysics Letter
Mechanical effects of optical resonators on driven trapped atoms: Ground state cooling in a high finesse cavity
We investigate theoretically the mechanical effects of light on atoms trapped
by an external potential, whose dipole transition couples to the mode of an
optical resonator and is driven by a laser. We derive an analytical expression
for the quantum center-of-mass dynamics, which is valid in presence of a tight
external potential. This equation has broad validity and allows for a
transparent interpretation of the individual scattering processes leading to
cooling. We show that the dynamics are a competition of the mechanical effects
of the cavity and of the laser photons, which may mutually interfere. We focus
onto the good-cavity limit and identify novel cooling schemes, which are based
on quantum interference effects and lead to efficient ground state cooling in
experimentally accessible parameter regimes.Comment: 17 pages, 6 figure
Dissipative quantum control of a spin chain
A protocol is discussed for preparing a spin chain in a generic many-body
state in the asymptotic limit of tailored non-unitary dynamics. The dynamics
require the spectral resolution of the target state, optimized coherent pulses,
engineered dissipation, and feedback. As an example, we discuss the preparation
of an entangled antiferromagnetic state, and argue that the procedure can be
applied to chains of trapped ions or Rydberg atoms.Comment: 5 pages, 4 figure
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