Spectral Analysis of Quantum Field Fluctuations in a Strongly Coupled Optomechanical System.

With a levitodynamics experiment in the strong and coherent quantum optomechanical coupling regime, we demonstrate that the oscillator acts as a broadband quantum spectrum analyzer. The asymmetry between positive and negative frequency branches in the displacement spectrum traces out the spectral features of the quantum fluctuations in the cavity field, which are thus explored over a wide spectral range. Moreover, in our two-dimensional mechanical system the quantum backaction, generated by such vacuum fluctuations, is strongly suppressed in a narrow spectral region due to a destructive interference in the overall susceptibility.

Josephson junctions loaded by transmission lines: a revisited problem.

The problem of evaluating dissipative effects in Josephson junctions loaded by transmission lines is reexamined, for either the symmetric or the asymmetric case, with particular consideration of the time domain in which the interaction between junction and load system occurs.

Reexamination of Josephson junctions coupled to transmission lines.

The effect of dissipation when due to the load of a transmission line coupled to a Josephson junction is reconsidered and evaluated by means of a simple direct procedure that supplies analytical expressions. The results are in good agreement with the ones previously reported in the literature. A simple criterion for testing experimental results is introduced.

Microwave variable waveguide attenuator.

A new type of cutoff attenuator is presented. The attenuator works in the X-band in conditions of almost perfect matching. This means that the phase of the wave, which propagates inside the guide, does not suffer sensible variation in the passage between X- and K(u)-bands.

Tunneling in frustrated total internal reflection: a comparison of different approaches.

Tunneling processes in frustrated total internal reflection are reexamined in order to compare the results already obtained from adopting a procedure based on a transition-element analysis with those recently reported on the basis of a statistical method applied to a Brownian-like motion. A close agreement between the two approaches can be established, at optical and microwave scales, when suitable values of the involved parameters are adopted.