Description
Optical clocks have now reached accuracies close to 1 x $10^{-18}$ [1] [2]. Thanks to their extremely low uncertainties, they are used as tools for various applications, such as chronometric geodesy, tests of General Relativity, search for physics beyond the Standard Model or redefinition of the SI second [3].
Mercury has not been much investigated in cold atoms or quantum gas experiments, and the properties of its various stable isotopes are still to be explored. Moreover, optical lattice clocks based on mercury are studied because of certain advantages over other neutral atoms. In particular, the mercury clock transition$ ^{1}S_0$ - $ ^{3}P_0$ has a low sensitivity to black-body radiation (BBR), that is to say the energy level shift due to the thermal radiation of an environment at a non zero temperature. Its sensitivity to BBR is 16 times lower than ytterbium and 30 times lower than strontium, two of the most successful clock species. It also has a high saturation vapor pressure favorable to implement a 2D magneto-optical trap as an efficient source of pre-cooled atoms. The mercury clock transition has a relatively high sensitivity to a putative variation of the fine structure constant [4], and hence allows to constrain theories aiming to unify gravity with other interactions and to search for dark matter. Working with mercury implies using UV-transitions which is one of the main experimental challenges. Developments of optical lattice clocks using mercury have been focusing so far on the $ ^{199}$Hg fermionic isotope [5][6].
The clock transition$ ^{1}S_0$ - $ ^{3}P_0$ of $ ^{199}$Hg is naturally allowed thanks to the hyperfine mixing due to the 1/2 nuclear spin of $ ^{199}$Hg. But the lifetime of the state $ ^{3}P_0$ is becoming smaller than the longer probing time allowed by the new generation of ultrastable lasers, so it is a limiting factor to fully exploit the potential of these novel technology lasers. Instead in bosonic isotopes with a zero nuclear spin, the $ ^{3}P_0$ state has hypothetically an unlimited lifetime. The $ ^{1}S_0$ - $ ^{3}P_0$ transition can be induced with an external magnetic field by a quenching scheme, and thereby giving the possibility to adapt the strength of this coupling to the probe laser characteristics [7]. $ ^{174}$Yb was studied with this method [8][9]. $ ^{88}$Sr clocks also based on this approach were also studied [10] and have shown promising accuracy [11].
In this poster, we will describe the laser cooling methods used, which open the way to study collisional properties. We will describe the optical lattice clock at SYRTE and we will report the achievement made so far on the $ ^{199}$Hg isotope (stability, accuracy budget, comparisons). We will mention limitations of our current setup and explain the scheme, the expectations and the future steps for making a clock using bosonic isotopes of mercury.
References
[1] W. F. McGrew et al., Nature 564, 87–90 (2018).
[2] A. D. Ludlow et al., Rev. Mod. Phys., 87:637–701, Jun 2015.
[3] S. Bize., C. R. Physique, 20(1):153–168, January 2019.
[4] E. J. Angstmann et al., Physical Review A, 70(1), Jul 2004.
[5] R. Tyumenev et al., New Journal of Physics, 18(11):113002, November 2016.
[6] K. Yamanaka et al., Phys. Rev. Lett., 114:230801, Jun 2015.
[7] A. V. Taichenachev et al., Physical Review Letters, 96(8):083001, March 2006.
[8] Z. W. Barber et al., Phys. Rev. Lett., 100:103002, Mar 2008.
[9] Z. W. Barber et al., Physical Review Letters, 96(8), Mar 2006.
[10] X. Baillard et al., Opt.Lett., 32(13):1812–1814, Jul 2007.
[11] S. Origlia et al., Phys. Rev. A, 98:053443, Nov 2018.
| Presenter name | Zyskind, Clara |
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