28,728 research outputs found
Splitting Sensitivity of the Ground and 7.6 eV Isomeric States of 229Th
The lowest-known excited state in nuclei is the 7.6 eV isomer of 229Th. This
energy is within the range of laser-based investigations that could allow
accurate measurements of possible temporal variation of this energy splitting.
This in turn could probe temporal variation of the fine-structure constant or
other parameters in the nuclear Hamiltonian. We investigate the sensitivity of
this transition energy to these quantities. We find that the two states are
predicted to have identical deformations and thus the same Coulomb energies
within the accuracy of the model (viz., within roughly 30 keV). We therefore
find no enhanced sensitivity to variation of the fine-structure constant. In
the case of the strong interaction the energy splitting is found to have a
complicated dependence on several parameters of the interaction, which makes an
accurate prediction of sensitivity to temporal changes of fundamental constants
problematical. Neither the strong- nor Coulomb-interaction contributions to the
energy splitting of this doublet can be constrained within an accuracy better
than a few tens of keV, so that only upper limits can be set on the possible
sensitivity to temporal variations of the fundamental constants.Comment: 4 pages, 2 figure
Loss-tolerant operations in parity-code linear optics quantum computing
A heavy focus for optical quantum computing is the introduction of
error-correction, and the minimisation of resource requirements. We detail a
complete encoding and manipulation scheme designed for linear optics quantum
computing, incorporating scalable operations and loss-tolerant architecture.Comment: 8 pages, 6 figure
Efficient Parity Encoded Optical Quantum Computing
We present a linear optics quantum computation scheme with a greatly reduced
cost in resources compared to KLM. The scheme makes use of elements from
cluster state computation and achieves comparable resource usage to those
schemes while retaining the circuit based approach of KLM
High power phase locked laser oscillators
The feasibility of mechanizing an adaptive array of independent laser oscillators for generation of a high power coherent output was experimentally investigated. Tests were structured to evaluate component/system requirements for delivery of energy to a low-earth orbit satellite. Initial experiments addressed the control issues of phase locking unstable resonators at low power levels. A successful phase lock demonstration formed the basis for the design and fabrication of the high power, water-cooled, control mirror subsequently installed in the NASA LeRC high power laser. Tests were performed to characterize the operational limits of the laser system and included quantitative assessment of the frequency stability, noise sources, and optical properties of the beam
Optimal cooling strategies for magnetically trapped atomic Fermi-Bose mixtures
We discuss cooling efficiency for different-species Fermi-Bose mixtures in
magnetic traps. A better heat capacity matching between the two atomic species
is achieved by a proper choice of the Bose cooler and the magnetically
trappable hyperfine states of the mixture. When a partial spatial overlap
between the two species is also taken into account, the deepest Fermi
degeneracy is obtained for an optimal value of the trapping frequency ratio.
This can be achieved by assisting the magnetic trap with a deconfining light
beam, as shown in the case of fermionic 6Li mixed with 23Na, 87Rb, and 133Cs,
with optimal conditions found for the not yet explored 6Li-87Rb mixture.Comment: 5 pages, 3 figures, to appear in Physical Review
Quantum Control of Qubits and Atomic Motion Using Ultrafast Laser Pulses
Pulsed lasers offer significant advantages over CW lasers in the coherent
control of qubits. Here we review the theoretical and experimental aspects of
controlling the internal and external states of individual trapped atoms with
pulse trains. Two distinct regimes of laser intensity are identified. When the
pulses are sufficiently weak that the Rabi frequency is much smaller
than the trap frequency \otrap, sideband transitions can be addressed and
atom-atom entanglement can be accomplished in much the same way as with CW
lasers. By contrast, if the pulses are very strong (\Omega \gg \otrap),
impulsive spin-dependent kicks can be combined to create entangling gates which
are much faster than a trap period. These fast entangling gates should work
outside of the Lamb-Dicke regime and be insensitive to thermal atomic motion.Comment: 16 pages, 15 figure
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