Investigating dark matter interactions using optical atomic clocks

Can dark matter interact with photons and influence atomic structure? A case for optical atomic clocks: Two different types of such clocks were compared at the Physikalisch-Technische Bundesanstalt (PTB) within the scope of the Collaborative Research Center DQ-mat and the Cluster of Excellence QuantumFrontiers. It is the most accurate search for an interaction of ultralight dark matter with photons to date.