Long spin-1/2 noble gas coherence times in mm-sized anodically bonded batch-fabricated ${}^3$He-${}^{129}$Xe-${}^{87}$Rb cells

As the only stable spin-1/2 noble gas isotopes, ${}^3$He and ${}^{129}$Xe are promising systems for inertial rotation sensing and searches for exotic spin couplings. Spin-1/2 noble gases have intrinsic coherence times on the order of hours to days, which allows for incredibly low frequency error of free-precession measurements. However relaxation in miniature cells is dominated by interactions with the cell wall, which limits the performance of a chip-scale sensor that uses noble gases. While ${}^{129}$Xe wall relaxation times have previously been limited to 10’s of seconds in mm-sized cells, we demonstrate the first anodically bonded batch-fabricated cells with dual ${}^3$He-${}^{129}$Xe isotopes and ${}^{87}$Rb in a 6~mm${}^3$ volume with ${}^3$He and ${}^{129}$Xe $T_2$ coherence times of, respectively, 4 h and 300 s. We use these microfabricated cells in a dual noble-gas comagnetometer and discuss its limits.