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  • Open Access

Direct measurement of the P03 clock state natural lifetime in Sr87

Jonathan Dolde1,*, Dhruva Ganapathy1,*, Xin Zheng1, Shuo Ma1, Kyle Beloy2, and Shimon Kolkowitz1,†

  • *These authors contributed equally to this work.
  • †Contact author: kolkowitz@berkeley.edu
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Phys. Rev. A 112, 023121 – Published 28 August, 2025

DOI: https://doi.org/10.1103/f6pt-flnt

Abstract

Optical lattice clocks based on the narrow (5s2)S01−(5s5p)P03 transition in neutral strontium (Sr) are among the most precise and accurate measurement devices in existence. Although this transition is completely forbidden by selection rules, state mixing from the hyperfine interaction in Sr87 provides a weakly allowed transition that can be coherently driven with practical clock laser intensities. While the coherent interrogation times of optical clocks are typically set by the linewidth of the probe laser, this limitation can be overcome in synchronous differential comparisons between ensembles. In such measurements the natural lifetime of the S01–P03 clock transition becomes the fundamental limiting factor to the duration of a single run of the experiment. However, a direct measurement of the decay rate of the clock excited state is quite challenging due to the competing effects of other loss channels such as Raman scattering, inelastic collisions, and atom loss due to background gas. In this work, we monitor the decay of Sr atoms trapped in an optical lattice and initialized in the P03 state. By making measurements of high and low density ensembles of both Sr87 and Sr88 across varying lattice trap depths, we isolate radiative decay, which accounts for a significant fraction of the observed decays at low depths. We obtain a natural radiative decay lifetime of 167−40+79 s for the P03 clock state in Sr87, a value that is consistent with previously reported measurements and theoretical predictions. We also introduce an additional measurement scheme that involves repeated measurements of the ground-state population within a single experimental sequence, validating our model and the consistency of the measured rates. We expect that the techniques introduced in this work are applicable to lifetime measurements of long-lived metastable states in other atoms and ions used for clocks and quantum computing. The results presented in this work inform performance estimates of proposed gravitational wave detectors and long-baseline atom interferometers making use of Sr87.

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Phys. Rev. A 112, 023121– Published 28 August, 2025
  • Received 9 May 2025
  • Accepted 29 July 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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