688 research outputs found
Influence of monolayer contamination on electric-field-noise heating in ion traps
Electric field noise is a hinderance to the assembly of large scale quantum
computers based on entangled trapped ions. Apart from ubiquitous technical
noise sources, experimental studies of trapped ion heating have revealed
additional limiting contributions to this noise, originating from atomic
processes on the electrode surfaces. In a recent work [A. Safavi-Naini et al.,
Phys. Rev. A 84, 023412 (2011)] we described a microscopic model for this
excess electric field noise, which points a way towards a more systematic
understanding of surface adsorbates as progenitors of electric field jitter
noise. Here, we address the impact of surface monolayer contamination on
adsorbate induced noise processes. By using exact numerical calculations for H
and N atomic monolayers on an Au(111) surface representing opposite extremes of
physisorption and chemisorption, we show that an additional monolayer can
significantly affect the noise power spectrum and either enhance or suppress
the resulting heating rates.Comment: 8 pages, 5 figure
Electric-field noise from carbon-adatom diffusion on a Au(110) surface: first-principles calculations and experiments
The decoherence of trapped-ion quantum gates due to heating of their motional
modes is a fundamental science and engineering problem. This heating is
attributed to electric-field noise arising from the trap-electrode surfaces. In
this work, we investigate the source of this noise by focusing on the diffusion
of carbon-containing adsorbates on the surface of Au(110). We show by density
functional theory, based on detailed scanning probe microscopy, how the carbon
adatom diffusion on the gold surface changes the energy landscape, and how the
adatom dipole moment varies with the diffusive motion. A simple model for the
diffusion noise, which varies quadratically with the variation of the dipole
moment, qualitatively reproduces the measured noise spectrum, and the estimate
of the noise spectral density is in accord with measured values.Comment: 8 pages, 6 figure
Trap-assisted complexes in cold atom-ion collisions
We theoretically investigate the trap-assisted formation of complexes in
atom-ion collisions and their impact on the stability of the trapped ion. The
time-dependent potential of the Paul trap facilitates the formation of
temporary complexes by reducing the energy of the atom, which gets temporarily
stuck in the atom-ion potential. As a result, those complexes significantly
impact termolecular reactions leading to molecular ion formation via three-body
recombination. We find that complex formation is more pronounced in systems
with heavy atoms, but the mass has no influence on the lifetime of the
transient state. Instead, the complex formation rate strongly depends on the
amplitude of the ion's micromotion. We also show that complex formation
persists even in the case of a time-independent harmonic trap. In this case, we
find higher formation rates and longer lifetimes than the Paul trap, indicating
that the atom-ion complex plays an essential role in atom-ion mixtures in
optical traps.Comment: 6 pages, 4 figure
Two-photon laser-scanning microscopy for single and repetitive imaging of dorsal and lateral spinal white matter in vivo
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