Time-dependent universal conductance fluctuations in mesoscopic Au wires: implications

In cold, mesoscopic conductors, two-level fluctuators lead to time-dependent universal conductance fluctuations (TDUCF) manifested as $1\mathrm{/}f$ noise. In Au nanowires, we measure the magnetic field dependence of TDUCF, weak localization (WL), and magnetic field-driven (MF) UCF before and after treatments that alter magnetic scattering and passivate surface fluctuators. Inconsistencies between $L_{\varphi }^{\mathrm{W}\mathrm{L}}$ and $L_{\varphi }^{\mathrm{T}\mathrm{D}\mathrm{U}\mathrm{C}\mathrm{F}}$ strongly suggest either that the theory of these mesoscopic phenomena in weakly disordered, highly pure Au is incomplete, or that the assumption that the TDUCF frequency dependence remains $1\mathrm{/}f$ to very high frequencies is incorrect. In the latter case, TDUCF in excess of $1\mathrm{/}f$ expectations may have implications for decoherence in solid-state qubits.