332 research outputs found
Deviation from exponential law and Van Hove's “lambda^2 t” limit
No full textThe deviations from a purely exponential behavior in a decay process are analyzed in relation to Van Hove’s “lambda^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
Charactering and measuring multitipartite entanglement
No full textA method is proposed to characterize and quantify multipartite entanglement in terms of the probability density function of bipartite entanglement over all possible balanced bipartitions of an ensemble of qubits. The method is tested on a class of random pure states
Alessandra Facchi, L'evoluzione del diritto fondiario algerino (1880-1986), 1987
No full textHenry Jean-Robert. Alessandra Facchi, L'evoluzione del diritto fondiario algerino (1880-1986), 1987. In: Droit et société, n°8, 1988. Le discours juridique. Langage, signification et valeurs, sous la direction de Eric Landowski. p. 127
The semiclassical limit of a quantum Zeno dynamics
No full textMotivated by a quantum Zeno dynamics in a cavity quantum electrodynamics setting, we study the asymptotics of a family of symbols corresponding to a truncated momentum operator, in the semiclassical limit of vanishing Planck constant h -> 0 and large quantum number N -> infinity, with hN kept fixed. In a suitable topology, the limit is the discontinuous symbol p chi(D) (x, p) where chi(D) is the characteristic function of the classically permitted region D in phase space. A refined analysis shows that the symbol is asymptotically close to the function p chi((N))(D) (x, p), where chi((N))(D) is a smooth version of chi(D) related to the integrated Airy function. We also discuss the limit from a dynamical point of view
Quantum Zeno and inverse quantum Zeno effects
No full textThe evolution of a quantum mechanical system can be profoundly modified
by the action of an external agent, such as a detection apparatus or a
field. If quantum measurements are performed on the system, its
evolution can be hindered or enhanced, depending on the physical
features of the system itself and the interaction.
The quantum Zeno effect consists in the hindrance of the evolution, the
inverse quantum Zeno effect in its enhancement. We shall discuss both
these effects by considering some examples in quantum optics and quantum
electrodynamics and shall critically analyze the notion of quantum
measurement: the Zeno effects take place both if the measurements are
``pulsed" and almost instantaneous or ``continuous" and of long
duration.
We also discuss the profound differences between oscillating systems,
whose Poincare' time is finite, and unstable ones.
For the latter, the Zeno effects are much more interesting and
transitions become possible between a Zeno and an inverse Zeno regime
La verità come interesse collettivo
No full textAssuming the truthfulness in political and institutional relations as a collective interest, this comment focuses on some implications, from the perspective of legal theory, of the statement of a general right to the truth. The author considers the conditions of its assumption as a fundamental right and discusses several aspects of the alethic rights proposed by Franca D’Agostini
Heisenberg scaling precision in the estimation of functions of parameters in linear optical networks
No full textWe propose a metrological strategy reaching Heisenberg-scaling precision in the estimation of functions of any fixed number p of arbitrary parameters encoded in a generic M-channel linear network. This scheme is experimentally feasible since it only employs a single-mode squeezed vacuum and homodyne detection on a single output channel. Two auxiliary linear networks are required and their role is twofold: to refocus the signal into a single channel after the interaction with the interferometer, and to fix the function of the parameters to be estimated according to the linear network analyzed. Although the refocusing requires some knowledge on the parameters, we show that the required precision on the prior measurement is achievable with a classic measurement. We conclude by discussing two paradigmatic schemes in which the choice of the auxiliary stages allows us to change the function of the unknown parameter to estimate
Pratica dei diritti umani e pluralismo giuridico nella ricerca antropologica
No full textStarting from different notions of human rights practice and from the anthropological debate on human rights, the author considers two different models of relationship between Human Rights and Legal pluralism. On the basis of some anthropological researches concerning the processes of localization of rights, she finally points out the existence of limits in these processes and the necessity to maintain a correspondence between human rights practice and the principles of human rights law and theory
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