Fig. 1: A schematic overview of the experimental principle.

a In the laboratory frame (LF) coordinate system z points vertically upwards, y points North and x points east. The fixed quantization axis B (pink arrow) in the LF coordinate system lies in the horizontal plane and points 20º south of x and probes different directions in the SCCEF as the Earth rotates around its axis (ω_⊕) and orbits the Sun (Ω_⊙). b In the LF a single ¹⁷²Yb⁺ ion is trapped in a segmented rf trap. Two coils generate a quantization field of 221 μT. The electron orbitals of the m_j = ± 1/2 and m_j = ± 7/2 Zeeman sublevels in the ²F_7/2 state orient themselves orthogonally to each other. The ²F_7/2 state is population via the E3 transition near 467 nm. The m_j substates are coupled via the rf magnetic field at ω_rf created with a coil that is placed 5.5 cm above the ion. c A simplified energy level diagram of ¹⁷²Yb⁺, showing the optical E3 transition and the transitions near 370 nm and 935 nm used for Doppler cooling and state detection.