Improved Limit on a Temporal Variation ofmp/mefrom Comparisons ofYb+and Cs Atom

Abstract

Accurate measurements of different transition frequencies between atomic levels of the electronic and hyperfine structure over time are used to investigate temporal variations of the fine structure constant α and the proton-to-electron mass ratio µ. We measure the frequency of the 2 S 1/2 → 2 F 7/2 electric octupole (E3) transition in 171 Yb + against two caesium fountain clocks as f (E3) = 642 121 496 772 645.36(25) Hz with an improved fractional uncertainty of 3.9×10 −16 . This transition frequency shows a strong sensitivity to changes of α. Together with a number of previous and recent measurements of the 2 S 1/2 → 2 D 3/2 electric quadrupole transition in 171 Yb + and with data from other elements, a least-squares analysis yields (1/α)(dα/dt) = −0.20(20) × 10 −16 /yr and (1/µ)(dµ/dt) = −0.5(1.6) × 10 −16 /yr, confirming a previous limit on dα/dt and providing the most stringent limit on dµ/dt from laboratory experiments. The search for variations of fundamental constants is motivated by theories unifying the fundamental interactions and is regarded as an opportunity to open a window to new physics with implications on cosmology as well as on particle physics [1][2][3][4]. While early proposals for such a search using atomic spectroscopy have been made shortly after the discovery of the expansion of the universe [5], sensitive observational and experimental tools became available only recently. Astrophysical observations of absorption spectra of interstellar matter have led to claims for [6][7][8] and against [9-13] variations of the fine structure constant α and the proton-to-electron mass ratio µ = m p /m e at relative uncertainties in the range 10 −5 to 10 −7 on a cosmological time scale of several billion years. In the laboratory, the high precision of atomic clocks that now reach relative uncertainties of 10 −16 and below in frequency ratios has been used to infer limits on variations of α and µ in the present epoch [14][15][16][17].In this Letter we present a high-accuracy absolute frequency measurement of the 2 S 1/2 → 2 F 7/2 electric octupole transition in 171 Yb + that possesses a strong sensitivity to changes of α. Together with recently reported frequency measurements of the 2 S 1/2 → 2 D 3/2 electric quadrupole transition in the same ion [18] this allows us to constrain possible temporal changes of both transition frequencies relative to caesium clocks. Besides confirming limits on dα/dt in the low 10 −17 /yr range these data provide the most stringent limit on dµ/dt from a laboratory experiment.171 Yb + is particularly attractive for a search for variations of fundamental constants because there are two transitions with low natural linewidth from the ground state to metastable states that have rather different electronic configurations [see Fig. 1(a)]. In case of the 2 S 1/2 (F = 0) → 2 D 3/2 (F = 2, m F = 0) electric quadrupole (E2) transition at 436 nm the 6s va- lence electron is promoted to the 5d level, while on the 2 S 1/2 (F = 0) → 2 F 7/2 (F = 3, m F = 0) electric octupole (E3) transitio...

An optimized ion trap geometry to measure quadrupole shifts of 171 Yb + clocks

“…Among them 171 Yb + is unique in the sense that it has three potential optical transitions that can be used for clocks [16]. Out of these there are two narrow 6s 2 S 1/2 (F = 0, m F = 0) → 5d 2 D 3/2 (F = 2, m F = 0) [17,18], 6s 2 S 1/2 (F = 0, m F = 0) → 5d 2 D 5/2 (F = 2, m F = 0) [19] quadrupole (E2) transitions and an ultra-narrow 6s 2 S 1/2 (F = 0, m F = 0) → 4f 13 6s 2 2 F 7/2 (F = 3, m F = 0) octupole (E3) transition [9,20] with their respective wavelengths at 435.5 nm, 411 nm and 467 nm. The transitions at the wavelengths 435.5 nm and 467 nm with low systematic shifts are the most suitable ones for precision frequency standards owing to their extremely small natural line-widths 3.02 Hz and 1 nHz, respectively.…”

Hyperfine-induced electric dipole contributions to the electric octupole and magnetic quadrupole atomic clock transitions

“…The work is in progress in many laboratories [19][20][21]. Measuring the ratio of frequency of this transition to the frequency of the 4f 14 6s 2 S 1/2 − 4f 14 5d 2 D 3/2 transition in the same ion put the strongest limit on the temporal variation of the fine structure constant and (by including the Cs hyperfine transition) on the proton-to-electron mass ratio [8,9,[22][23][24]. The use of the electric octupole transition in Yb + for the search of LLI violation may lead to five orders of magnitude improvement over current best bounds on the LLI violation in the electron-photon sector [11].…”

“…The 171 Yb + ions are used by several experimental groups as prospective optical clocks of an exceptional high accuracy [20,21,23,24,35]. Current best limits on the temporal variation of the fine structure constant come from the comparison of the frequencies of the 4f 14 6s 2 S 1/2 -4f 13 6s 2 3 F 2/2 E3 and 4f 12 6s 2 S 1/2 -4f 14 5d 2 D 3/2 E2 transitions [8,9,23,24]. The results for the hyperfine structure are presented in Table I.…”

Frequency and time transfer for metrology and beyond using telecommunication network fibres

“…This outstanding performance makes them ideal tools for laboratory tests of the validity of General Relativity (see for instance [7,9,10]). Among them, the comparison of different types of clocks is used to detect possible temporal variations of fundamental physical constants [11][12][13]. More generally, accurate time and frequency transfer is essential for relativistic geodesy, high-resolution radio astronomy, and is the basis of almost every type of precision measurement.…”