A compact, multichannel, and low noise arbitrary waveform generator.

A new type of high functionality, fast, compact, and easy programmable arbitrary waveform generator for low noise physical measurements is presented. The generator provides 7 fast differential waveform channels with a maximum bandwidth up to 200 MHz frequency. There are 6 fast pulse generators on the generator board with 78 ps time resolution in both duration and delay, 3 of them with amplitude control.

Probing noise in flux qubits via macroscopic resonant tunneling.

Macroscopic resonant tunneling between the two lowest lying states of a bistable rf SQUID is used to characterize noise in a flux qubit. Measurements of the incoherent decay rate as a function of flux bias revealed a Gaussian-shaped profile that is not peaked at the resonance point but is shifted to a bias at which the initial well is higher than the target well. The rms amplitude of the noise, which is proportional to the dephasing rate 1/tauphi, was observed to be weakly dependent on temperature below 70 mK.

Attention and size in a global/local task.

Two-letter stimuli, consisting of one small letter inside a much larger one (in Experiments 1A, 1B, and 2) or inside a "blob" (in Experiment 3), were used to examine the role of size difference in global/local tasks. The small letter was placed at locations that avoided contour interactions. The results showed no identity interference, in that the specific identity of the large letter did not differentially affect identification of the small one.

Time-resolved second-harmonic study of femtosecond laser-induced disordering of GaAs surfaces.

An abrupt (less than 100 fs) decrease in the second-harmonic intensity reflected from the surface of a GaAs (110) wafer has been observed experimentally. The linear reflectivity was found to increase on a time scale of ~1 ps. Thus the concept of fast atomic disorder induced by electronic excitation within a relatively cold lattice is given new experimental support.