Atomic Clocks with Suppressed Blackbody Radiation Shift

Abstract

We develop a nonstandard concept of atomic clocks where the blackbody radiation shift (BBRS) and its temperature fluctuations can be dramatically suppressed (by one to three orders of magnitude) independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ν 1 and ν 2 ) which are exposed to the same thermal environment, there exists a "synthetic" frequency ν syn ∝ (ν 1 − ε 12 ν 2 ) largely immune to the BBRS. As an example, it is shown that in the case of 171 Yb + it is possible to create a clock in which the BBRS can be suppressed to the fractional level of 10 −18 in a broad interval near room temperature (300±15 K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ν 1 and ν 2 . Here the frequency ν syn is generated as one of the components of the comb spectrum and can be used as an atomic standard.PACS numbers: 03.75. Dg, 37.25.+k, 42.62.Fi The main progress in modern fundamental metrology is connected with the development of atomic clocks. The most promising frequency standards today are based on single trapped ions [1] and on ensembles of neutral atoms confined to an optical lattice at the magic wavelength [2,3]. It is believed that these clocks can provide frequency references with unprecedented small systematic uncertainties in the 10 −17 -10 −18 range. This progress will probably lead to a redefinition of the unit of Time and to new fundamental tests of physical theories in particular in the fields of General Relativity, cosmology, and unification of the fundamental interactions [4,5].The largest effect that contributes to the systematic uncertainty of many atomic clocks is the interaction of the thermal blackbody radiation with the atomic eigenstates. This effect was first considered in 1982 for cesium atomic clocks [6], but remains up to now a major problem for many modern atomic time and frequency standards. At present there exist three approaches to tackle the blackbody radiation shift (BBRS) problem. The first one is the use of cryogenic techniques to suppress this shift to a negligible level. This approach is pursued for the mercury ion clock [7], for the Cs fountain clock [8], and for the Sr optical lattice clock [9]. The second approach is the precise temperature stabilization of the experimental setup in combination with theoretical and/or semiempirical numerical calculations of the shift at given temperature [10,11]. The third approach is based on the * e-mail address: viyudin@mail.ru † also PTB choice of an atom or ion where both levels of the reference transition have approximately the same BBRS. Here the most promising candidate is 27 Al + with a fractional BBRS of the reference transition frequency of ∼10 −17 [1,12], followed by 115 In + [13,14]. However, the latter approach limits the choice of candidates for tests of fundamental theories.In the present paper we propose an alternative method allowing us to suppress the ...

Neutral Atom Frequency Reference in the Deep Ultraviolet withFractional Uncertainty=5.7×10−15

“…The accuracy of microwave clocks has improved at a rate of ∼10 per decade and now optical clocks are showing an improvement at a rate > 10 2 per decade [1]. Optical clock technology is still relatively young; yet four atomic species have demonstrated line-center frequency uncertainties at or below 10 −16 [2][3][4], with the potential of several more to follow [5][6][7][8]. This will enable further precision in tests searching for new physics in the low energy regime [9][10][11].…”

Correlation effects in Yb+and implications for parity violation

“…Then, we solved the RPA equations, which are equivalent to the summation of the corresponding many-body diagrams to all orders for both d and H SD operators in Eq. (8). Smaller contributions that include core-Brueckner, structural radiation, and normalization corrections were also taken into account.…”

Synthetic frequency protocol for Ramsey spectroscopy of clock transitions

“…Previously in the paper [32] the so-called synthetic frequency method, allowing to radically suppress thermal (BBR) shift in atomic clock, was proposed. However, an ideology of this method can be easy extended on cancelling of arbitrary systematic shift.…”

“…Our approach is based on adaptation of so-called synthetic frequency concept [32] to the Ramsey spectroscopy with the use of interrogations for different durations of free evaluation intervals. We show that this protocol in combination with the original hyper-Ramsey scheme [28] makes most extremal results and is quite stable with respect to the decoherence.…”