arXiv subjects

P. Facchi

Publications and source records attributed to P. Facchi.

75 records · Page 5Linked to original sources

arXiv1999

Deviations from exponential law and Van Hove's "λ^2 t" limit

The deviations from a purely exponential behavior in a decay process are analyzed in relation to Van Hove's "λ^2 t" limiting procedure. Our attention is focused on the effects that arise when the coupling constant is small but nonvanishing. We first consider a simple model (two-level atom in interaction with the electromagnetic field), then gradually extend our analysis to a more general framework. We estimate all deviations from exponential behavior at leading orders in the coupling constant.

quant-ph↗

arXiv1999

Berry phase from a quantum Zeno effect

We exhibit a specific implementation of the creation of geometrical phase through the state-space evolution generated by the dynamic quantum Zeno effect. That is, a system is guided through a closed loop in Hilbert space by means a sequence of closely spaced projections leading to a phase difference with respect to the original state. Our goal is the proposal of a specific experimental setup in which this phase could be created and observed. To this end we study the case of neutron spin, examine the practical aspects of realizing the "projections," and estimate the difference between the idealized projections and the experimental implementation.

quant-ph↗

arXiv1999

Measurement-induced quantum diffusion

The dynamics of a kicked quantum system undergoing repeated measurements of momentum is investigated. A diffusive behavior is obtained even when the dynamics of the classical counterpart is not chaotic. The diffusion coefficient is explicitly computed for a large class of Hamiltonians and compared to the classical case.

quant-ph↗