1/f flux noise induced by spin glasses in superconducting qubits

Recently, it has been realized that the coherence time of flux qubits is limited by unknown sources of flux noise, which exhibits a 1/f spectrum at low frequencies f <or similar 10 kHz and at low temperatures <or similar 5 K. Experiments suggest that the main contribution to the flux noise may be produced by paramagnetic spins located on the surface of the superconducting loop. We consider a spin glass system of classical Heisenberg spins and investigate the low frequency dynamics of the total magnetization at temperatures near the spin glass freezing temperature. We discuss the role of anisotropy and temperature on the shape of the noise spectrum.