Universal non-equilibrium dielectric losses in amorphous solids at microwave frequencies and ultra-low temperatures

We show that during the fast application of an external DC field AC dielectric losses of an ensemble of two level systems (TLS) in amorphous solids becomes universal in a wide range of temperatures and frequencies of AC field. These losses are determined by the bare linear dielectric permittivity in the low temperature limit. Theoretical predictions agree with the recent experimental findings and suggest novel measurements capable of extracting both the TLS density and the TLS dipole size, separately.