6,447 research outputs found
Spin flip lifetimes in superconducting atom chips: BCS versus Eliashberg theory
We investigate theoretically the magnetic spin-flip transitions of neutral
atoms trapped near a superconducting slab. Our calculations are based on a
quantum-theoretical treatment of electromagnetic radiation near dielectric and
metallic bodies. Specific results are given for rubidium atoms near a niobium
superconductor. At the low frequencies typical of the atomic transitions, we
find that BCS theory greatly overestimates coherence effects, which are much
less pronounced when quasiparticle lifetime effects are included through
Eliashberg theory. At 4.2 K, the typical atomic spin lifetime is found to be
larger than a thousand seconds, even for atom-superconductor distances of one
micrometer. This constitutes a large enhancement in comparison with normal
metals.Comment: 10 pages, 4 figure
River environment: a reference document, The
DBS-PFL-YHC-SAS-14.Includes bibliographical references (pages A-1-A-26).Prepared for United States of the Interior Fish and Wildlife Service.December 1975
Pattern Views: Concept and Tooling for Interconnected Pattern Languages
Patterns describe proven solutions for recurring problems. Typically,
patterns in a particular domain are interrelated and organized in pattern
languages. As real-world problems often require patterns of multiple domains,
different pattern languages have to be considered to address these problems.
However, cross-domain knowledge about how patterns of different languages
relate to each other is either hidden in individual pattern descriptions or not
documented at all. This makes it difficult to identify relevant patterns across
pattern languages. Therefore, we introduce a concept and tooling that enables
to capture patterns and their relations across pattern languages for a
particular problem context
Performance of a 229 Thorium solid-state nuclear clock
The 7.8 eV nuclear isomer transition in 229 Thorium has been suggested as an
etalon transition in a new type of optical frequency standard. Here we discuss
the construction of a "solid-state nuclear clock" from Thorium nuclei implanted
into single crystals transparent in the vacuum ultraviolet range. We
investigate crystal-induced line shifts and broadening effects for the specific
system of Calcium fluoride. At liquid Nitrogen temperatures, the clock
performance will be limited by decoherence due to magnetic coupling of the
Thorium nucleus to neighboring nuclear moments, ruling out the commonly used
Rabi or Ramsey interrogation schemes. We propose a clock stabilization based on
counting of flourescence photons and present optimized operation parameters.
Taking advantage of the high number of quantum oscillators under continuous
interrogation, a fractional instability level of 10^{-19} might be reached
within the solid-state approach.Comment: 28 pages, 9 figure
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