65,879 research outputs found
Scaling of the low temperature dephasing rate in Kondo systems
We present phase coherence time measurements in quasi-one-dimensional Ag
wires doped with Fe Kondo impurities of different concentrations . Due to
the relatively high Kondo temperature of this system, we
are able to explore a temperature range from above down to below . We show that the magnetic contribution to the dephasing rate
per impurity is described by a single, universal curve when plotted as a
function of . For , the dephasing rate is remarkably well
described by recent numerical results for spin impurities. At lower
temperature, we observe deviations from this theory. Based on a comparison with
theoretical calculations for , we discuss possible explanations for the
observed deviations.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Generation of a decoherence-free entangled state using a radio frequency dressed state
We propose the generation of entangled states with trapped calcium ions using
a combination of an rf dressed state and a spin dependent force. Using this
method, a decoherence-free entangled state of rf qubits can be directly
generated and ideally its fidelity is close to unity. We demonstrate an rf
entangled state with a fidelity of 0.68, which has a coherence time of more
than 200 ms by virtue of the fact that it is an eigenstate with energy gaps
between adjacent levels.Using the same technique, we also produce a
qutrit-qutrit entangled state with a fidelity of 0.77, which exceeds the
threshold value for separability of 2/3.Comment: 4 figure
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