Precision optical frequency measurements and coherent spectroscopy with a single trapped ion standard
Bibliographic record
Abstract
A single ion, trapped, laser cooled and probed on an ultra- narrow transition, provides what is widely considered the best approximation to an ideal, isolated optical frequency reference. Our group has been actively studying the 445-THz (674 nm), 5s2S1/2-4d2D5/2 transition in 88Sr+. Individual Zeeman component linewidths of 250 Hz were observed and a probe laser system was locked to the center frequency of the Zeeman spectrum. A cesium-based frequency chain was used to measure the center frequency of the 88Sr+ S-D spectrum to an accuracy of 200 Hz. Under our current experimental conditions, the magnitudes of the systematic shifts in the linecenter position are estimated to be less than 1 part in 1015. As part of our efforts in improving the trapped ion standard, we have studied the coherent excitation of a single ion via Rabi pulse and Ramsey fringe interrogation. Initial results yielding Ramsey fringe widths down to 840 Hz were obtained, and some decoherence and motional properties of the ion system were investigated. The Sr+ standard was applied recently to the well-known He- Ne/I2 standard at 633 nm. This measurement provided an accuracy comparison between a traditional frequency chain and a femtosecond laser frequency comb. In addition, after several months and transportation over a significant portion of the globe, 88Sr+ calibrated 633 nm lasers from NRC and BIPM have shown agreement to 1 kHz in their originally determined absolute optical frequencies. The results of these intercomparisons point to potential worldwide accuracy improvement of working 633 nm radiation standards.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".