Absolute frequency measurement of a <sup>88</sup>Sr<sup>+</sup> clock by direct comparison to a primary frequency standard
Bibliographic record
Abstract
Abstract We report on a measurement of the absolute frequency of the 88 Sr + clock transition via a direct comparison to our cesium fountain clock, National Research Council Canada (NRC)-FCs2. The measurement yield a value of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>444</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>779</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>044</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>095</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>485.404</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.045</mml:mn> </mml:mrow> </mml:math> Hz. The corresponding fractional uncertainty of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>1.0</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> is, to our knowledge, the lowest so far reported for an absolute frequency measurement. The low uncertainty obtained is primarily a consequence of improvements to NRC-FCs2, specifically a systematic uncertainty of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>9.3</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>17</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> and a stability of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>6.3</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> </mml:msup> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msqrt> <mml:mi>τ</mml:mi> </mml:msqrt> </mml:mrow> </mml:math> . The measurement was made over a period of 37 days with 68% uptime, for a total measurement time of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>2.16</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> s. The 88 Sr + frequency was also compared to terrestrial time via a global navigation satellite system (GNSS) link to Universal Coordinated Time, yielding a frequency value of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>444</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>779</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>044</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>095</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mn>485.406</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.089</mml:mn> </mml:mrow> </mml:math> Hz, which is in agreement with the direct comparison with NRC-FCs2.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.027 | 0.013 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.004 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 teacher head, 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".