We show that charge noise SQ in Josephson qubits can be produced by fluctuating two level systems (TLS) with electric dipole moments in the substrate using a flat density of states. At high frequencies the frequency and temperature dependence of the charge noise depends on the ratio J/Jc of the electromagnetic flux J to the critical flux Jc. It is not widely appreciated that TLS in small qubits can easily be strongly saturated with J/Jc≫1. Our results are consistent with experimental conclusions that SQ∼1/f at low frequencies and SQ∼f at high frequencies.
@article{arxiv.0707.1514,
title = {Effect of Two Level System Saturation on Charge Noise in Josephson Junction Qubits},
author = {Clare C. Yu and Magdalena Constantin and John M. Martinis},
journal= {arXiv preprint arXiv:0707.1514},
year = {2011}
}