  Ultra-high frequency gravitational waves in the MHz to THz regime promise a
unique possibility to probe the very early universe, particle physics at very
high energies and exotic astrophysical objects - but achieving the sensitivity
required for detection is an immense challenge. This is a brief summary of
recent progress in electromagnetic high-frequency gravitational wave searches,
which are based on classical electromagnetism in a space-time perturbed by
gravitational waves. A particular focus is given to synergies with axion
searches and atomic precision measurements. This article was prepared as
proceedings for Moriond EW 2023.
