A Compact Physics Package of a Chip-Scale Atomic Clock with a Built-in Magnetic Shield

We demonstrate a physics package for chip-scale atomic clocks in which the supporting frame itself serves as a primitive magnetic shield (∼20x attenuation). It measures 4.9×4.9×4.5 mm
³
with its frequency instability ∼ 10
⁻¹⁰
at 1 s.