Magdalena Constantin

Experimental Persistence Probability for Fluctuating Steps

The persistence behavior for fluctuating steps on the Si(111)-(sqrt[3]xsqrt[3])R30 degrees -Al surface was determined by analyzing time-dependent STM images for temperatures between 770 and 970 K. Using the standard persistence definition, the measured persistence probability displays power-law decay with an exponent of theta=0.77+/-0.03. This is consistent with the value of theta=3/4 predicted for attachment-detachment limited step kinetics. If the persistence analysis is carried out in terms of return to a fixed-reference position, the measured probability decays exponentially. Numerical studies of the Langevin equation used to model step motion corroborate the experimental observations.

Microscopic Model of Critical Current Noise in Josephson Junctions

We present a simple microscopic model to show how fluctuating two-level systems in a Josephson junction tunnel barrier of thickness L can modify the potential energy of the barrier and produce critical current noise spectra. We find low frequency 1/f noise that goes as L5. Our values are in good agreement with recent experimental measurements of critical current noise in Al/AlOx/Al Josephson junctions. We also investigate the sensitivity of the noise on the nonuniformity of the tunnel barrier.

Saturation of two-level systems and charge noise in Josephson junction qubits

We study the charge noise

Survival in equilibrium step fluctuations

{S}_{Q}

Spatial persistence and survival probabilities for fluctuating interfaces

in Josephson qubits produced by fluctuating two-level systems (TLSs) with electric-dipole moments in the substrate. The TLSs are driven by an alternating electric field of angular frequency

Persistence and survival in equilibrium step fluctuations

\ensuremath{\Omega}

Infinite family of persistence exponents for interface fluctuations

and electric field intensity

Effect of Two Level System Saturation on Charge Noise in Josephson Junction Qubits

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Microscopic Model of 1/f Noise in Josephson Junctions

. It is not widely appreciated that TLS in small qubits can easily be strongly saturated if

1/f Noise in Josephson Junctions

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