[
 {
  "value": "4.1e-17",
  "sigma": "1.6e-17",
  "source": "Chou, Hume, Rosenband, Wineland, Science 329, 1630",
  "year": "2010",
  "field": "timekeeping",
  "id": "T1",
  "unit": "1",
  "quantity": "Al+ clocks 33 cm apart, fractional rate difference",
  "grade": "recalled: secondary source (blog of 2010-09-24) gives about 4e-17, the 1.6e-17 not found in a fetched primary text, PRIOR-ART row 2",
  "bound_low": "",
  "bound_high": "",
  "recalled": "yes"
 },
 {
  "value": "9.8e-20",
  "sigma": "2.3e-20",
  "source": "Bothwell et al., Nature 602, 420 (arXiv 2109.12238, final gradient -9.8(2.3) x 10^-20 per mm, sign is the coordinate convention of their Fig. 1a, predicted -1.09 x 10^-19)",
  "year": "2022",
  "field": "timekeeping",
  "id": "T2",
  "unit": "per mm",
  "quantity": "Sr lattice rate gradient magnitude per mm",
  "grade": "primary, PRIOR-ART row 1",
  "bound_low": "",
  "bound_high": "",
  "recalled": "no"
 },
 {
  "value": "1.4e-5",
  "sigma": "9.1e-5",
  "source": "Takamoto et al., Nature Photonics 14, 411 (Tokyo Skytree, 450 m), as restated in arXiv 2502.06104",
  "year": "2020",
  "field": "timekeeping",
  "id": "T3",
  "unit": "1",
  "quantity": "redshift violation parameter alpha",
  "grade": "secondary (review by the same group), PRIOR-ART row 3",
  "bound_low": "",
  "bound_high": "",
  "recalled": "no"
 },
 {
  "value": "1.0e-18",
  "sigma": "1.1e-18",
  "source": "Lange et al., Phys Rev Lett 126, 011102 (arXiv 2010.06620), Yb+ E3/E2",
  "year": "2021",
  "field": "timekeeping",
  "id": "T4",
  "unit": "per yr",
  "quantity": "drift of alpha, (1/alpha) dalpha/dt",
  "grade": "primary abstract, PRIOR-ART row 4",
  "bound_low": "",
  "bound_high": "",
  "recalled": "no"
 }
]