Gravitational waves at frequencies well above 1 kHz may offer interesting opportunities to detect primordial black hole mergers, very early cosmological phase transitions, or QCD dynamics during neutron star mergers. After briefly reviewing these potential sources, we will highlight some of the most important proposed detection technologies, in particular microwave cavities and atomic clocks. While current sensitivities still fall several orders of magnitude short of probing realistic signals, rapid progress in quantum technology may spark hope that this could change in the future.