779 research outputs found
Prospects for stored ion frequency standards
Fundamental limitations of possible frequency standards based on stored ions are examined. Practical limitations are also addressed but without regard to size, power consumption, and cost. With these guidelines, one can anticipate that a stored ion frequency standard with accuracy and stability better than 10 to the -15th power is now possible
Transport quantum logic gates for trapped ions
Many efforts are currently underway to build a device capable of large scale
quantum information processing (QIP). Whereas QIP has been demonstrated for a
few qubits in several systems, many technical difficulties must be overcome in
order to construct a large-scale device. In one proposal for large-scale QIP,
trapped ions are manipulated by precisely controlled light pulses and moved
through and stored in multizone trap arrays. The technical overhead necessary
to precisely control both the ion geometrical configurations and the laser
interactions is demanding. Here we propose methods that significantly reduce
the overhead on laser beam control for performing single and multiple qubit
operations on trapped ions. We show how a universal set of operations can be
implemented by controlled transport of ions through stationary laser beams. At
the same time, each laser beam can be used to perform many operations in
parallel, potentially reducing the total laser power necessary to carry out QIP
tasks. The overall setup necessary for implementing transport gates is simpler
than for gates executed on stationary ions. We also suggest a transport-based
two-qubit gate scheme utilizing microfabricated permanent magnets that can be
executed without laser light.Comment: 31 pages, 5 figures, minor improvements in figures and notation,
submitted to PR
Observation of the 1S0 - 3P0 clock transition in 27Al+
We report for the first time, laser spectroscopy of the 1S0 - 3P0 clock
transition in 27Al+. A single aluminum ion and a single beryllium ion are
simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb
repulsion. This coupling allows the beryllium ion to sympathetically cool the
aluminum ion, and also enables transfer of the aluminum's electronic state to
the beryllium's hyperfine state, which can be measured with high fidelity.
These techniques are applied to a measurement of the clock transition
frequency, \nu = 1 121 015 393 207 851(8) Hz. They are also used to measure the
lifetime of the metastable clock state, \tau = 20.6 +/- 1.4 s, the ground state
1S0 g-factor, g_S = -0.00079248(14), and the excited state 3P0 g-factor, g_P =
-0.00197686(21), in units of the Bohr magneton.Comment: 4 pages, 2 figures; updated author lis
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
Enhancement of laser cooling by the use of magnetic gradients
We present a laser cooling scheme for trapped ions and atoms using a
combination of laser couplings and a magnetic gradient field. In a
Schrieffer-Wolff transformed picture, this setup cancels the carrier and blue
sideband terms completely resulting in an improved cooling behaviour compared
to standard cooling schemes (e.g. sideband cooling) and allowing cooling to the
vibrational ground state. A condition for optimal cooling rates is presented
and the cooling behaviour for different Lamb-Dicke parameters and spontaneous
decay rates is discussed. Cooling rates of one order of magnitude less than the
trapping frequency are achieved using the new cooling method. Furthermore the
scheme turns out to be robust under deviations from the optimal parameters and
moreover provides good cooling rates also in the multi particle case.Comment: 14 pages, 8 figure
Compact Toroidal Ion Trap Design and Optimization
We present the design of a new type of compact toroidal, or "halo", ion trap.
Such traps may be useful for mass spectrometry, studying small Coulomb cluster
rings, quantum information applications, or other quantum simulations where a
ring topology is of interest. We present results from a Monte Carlo
optimization of the trap design parameters using finite-element analysis
simulations that minimizes higher-order anharmonic terms in the trapping
pseudopotential, while maintaining complete control over ion placement at the
pseudopotential node in 3D using static bias fields. These simulations are
based on a practical electrode design using readily-available parts, yet can be
easily scaled to any size trap with similar electrode spacings. We also derive
the conditions for a crystal phase transition for two ions in the compact halo
trap, the first non-trivial phase transition for Coulomb crystals in this
geometry.Comment: 8 pages, 9 figure
Cooling the Collective Motion of Trapped Ions to Initialize a Quantum Register
We report preparation in the ground state of collective modes of motion of
two trapped 9Be+ ions. This is a crucial step towards realizing quantum logic
gates which can entangle the ions' internal electronic states. We find that
heating of the modes of relative ion motion is substantially suppressed
relative to that of the center-of-mass modes, suggesting the importance of
these modes in future experiments.Comment: 5 pages, including 3 figures. RevTeX. PDF and PostScript available at
http://www.bldrdoc.gov/timefreq/ion/qucomp/papers.htm . final (published)
version. Eq. 1 and Table 1 slightly different from original submissio
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