Related papers: Validating a lutetium frequency reference
The fluctuation relation, a milestone of modern thermodynamics, is only established when a set of fundamental currents can be measured. Here we prove that it also holds for systems with hidden transitions if observations are carried ``at…
We present the new absolute frequency measurement of ytterbium (171Yb) obtained at INRiM with the optical lattice clock IT-Yb1 against the cryogenic caesium (133Cs) fountain IT-CsF2, evaluated through a measurement campaign that lasted 14…
The quantum variables that can be accessed directly by experiments are described by observables. Therefore, physical parameters can only be evaluated indirectly, via estimations based on experimental measurement results. I show that the…
With 87-Sr atoms confined in a one dimensional optical lattice, the frequency of the optical clock transition 5s^2 ^1S_0 - 5s5p ^3P_0 has been determined to be 429 228 004 229 872.9(5) Hz. The transition frequency was measured with the help…
Recent developments in frequency metrology and optical clocks have been based on electronic transitions in atoms and singly charged ions as references. These systems have enabled relative frequency uncertainties at a level of a few parts in…
We report a single-ion optical atomic clock with fractional frequency uncertainty of $5.5\times10^{-19}$ and fractional frequency stability of $3.5 \times10^{-16}/\sqrt{\tau/\mathrm{s}}$, based on quantum logic spectroscopy of a single…
We have remeasured the absolute $1S$-$2S$ transition frequency $\nu_{\rm {H}}$ in atomic hydrogen. A comparison with the result of the previous measurement performed in 1999 sets a limit of $(-29\pm 57)$ Hz for the drift of $\nu_{\rm {H}}$…
We present the first precise frequency measurement of the 2$^{1}$S$_{0}$-3$^{1}$D$_{2}$ two-photon transition in $^{4}$He at 1009 nm. The laser source at 1009 nm is stabilized on an optical frequency comb to perform the absolute frequency…
We report the frequency measurement with an accuracy in the 100 kHz range of several optical transitions of atomic Sr : $^1S_0- ^3P_1$ at 689 nm, $^3P_1- ^3S_1$ at 688 nm and $^3P_0- ^3S_1$ at 679 nm. Measurements are performed with a…
Based on general relativity, clock comparisons enable the determination of the gravity potential relative to a stable reference. Lunar surface clocks, owing to the Moon's low-noise conditions, high orbital stability, and broad Earth…
We numerically evaluate the expected performances of an optical frequency standard at 729 nm based on a single calcium ion. The frequency stability is studied through the Allan deviation and its dependence on the excitation method (single…
The hydrogen molecule has become a test ground for quantum electrodynamical calculations in molecules. Expanding beyond studies on stable hydrogenic species to the heavier radioactive tritium-bearing molecules, we report on a measurement of…
We experimentally investigate an optical clock based on $^{171}$Yb ($I=1/2$) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including a density-dependent collision shift, with a…
We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in $^{229}$Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the…
Excursions far from their equilibrium structures can bring crystalline solids through collective transformations including transitions into new phases that may be transient or long-lived. Direct spectroscopic observation of…
Caesium fountain frequency-standards realize the second in the International System of Units with a relative uncertainty approaching 10^-16. Among the main contributions to the accuracy budget, cold collisions play an important role because…
The mass sensitivity of the vibration-rotation-inversion transitions of H$_3{}^{16}$O$^+$, H$_3{}^{18}$O$^+$, and D$_3{}^{16}$O$^+$ is investigated variationally using the nuclear motion program TROVE~\citep{TROVE:2007}. The calculations…
We report on the observation of a dc Stark frequency shift at the $10^{-13}$ level by comparing two strontium optical lattice clocks. This frequency shift arises from the presence of electric charges trapped on dielectric surfaces placed…
Relativistic corrections are essential for time transformations between geocentric, solar system barycentric, and luni-centric reference systems to account for differences in gravitational potential and relative motion. As the primary…
To operate an optical lattice clock at a fractional uncertainty below $10^{-17}$, one must typically consider not only electric-dipole (E1) interaction between an atom and the lattice light field when characterizing the resulting lattice…