<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>Sr</mml:mi><mml:none/><mml:mo>+</mml:mo><mml:mprescripts/><mml:none/><mml:mn>88</mml:mn></mml:mmultiscripts></mml:math>445-THz Single-Ion Reference at the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>−</mml:mo><mml:mn>17</mml:mn></mml:mrow></mml:msup></mml:math>Level via Control and Cancellation of Systematic Uncertainties and Its Measurement against the SI Second
Bibliographic record
Abstract
We describe experiments and measurements on a trapped and laser-cooled single ion of $^{88}\mathrm{Sr}^{+}$ which, when probed on its reference $5s\text{ }^{2}S_{1/2}\ensuremath{\rightarrow}4d\text{ }^{2}D_{5/2}$ transition at 445 THz, provides an optical frequency standard of evaluated accuracy outperforming the current realization of the SI second. Studies are presented showing that micromotion-associated shifts of the standard can be reduced to the ${10}^{\ensuremath{-}18}$ level and uncertainties in the blackbody-induced shifts for the current system are at the low ${10}^{\ensuremath{-}17}$ level due to the relatively well-known polarizability of the strontium ion system and careful choice of the trap structure. The current evaluated systematic shifts for the ion transition are at a fractional uncertainty of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$. An absolute frequency measurement performed over a two-month period relative to a maser referenced to the SI second via Global Positioning System time transfer has determined the center frequency for the transition at ${\ensuremath{\nu}}_{SD}=444\text{ }779\text{ }044\text{ }095\text{ }485.5\ifmmode\pm\else\textpm\fi{}0.9\text{ }\text{ }\mathrm{Hz}$ ($1\ensuremath{\sigma}$).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.282 | 0.196 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".