In a recent publication [Phys. Rev. A 79, 065602 (2009)] it was shown that an avoided-crossing resonance can be defined in different ways, according to level-structural or dynamical aspects, which do not coincide in general. Here a simple $3$-level s
ystem in a $Lambda$ configuration is discussed, where the difference between both definitions of the resonance may be observed. We also discuss the details of a proposed experiment to observe this difference, using microwave fields coupling hyperfine magnetic sublevels in alkali atoms.
We study the dynamics of neutral cold atoms in an $L$-shaped crossed-beam optical waveguide formed by two perpendicular red-detuned lasers of different intensities and a blue-detuned laser at the corner. Complemented with a vibrational cooling proces
s this setting works as a one-way device or atom diode.
A relation is found between pulsed measurements of the excited state probability of a two-level atom illuminated by a driving laser, and a continuous measurement by a second laser coupling the excited state to a third state which decays rapidly and i
rreversibly. We find the time between pulses to achieve the same average detection time than a given continuous measurement in strong, weak, or intermediate coupling regimes, generalizing the results in L. S. Schulman, Phys. Rev. A 57, 1509 (1998).
Repeated measurements of a quantum particle to check its presence in a region of space was proposed long ago [G. R. Allcock, Ann. Phys. {bf 53}, 286 (1969)] as a natural way to determine the distribution of times of arrival at the orthogonal subspace
, but the method was discarded because of the quantum Zeno effect: in the limit of very frequent measurements the wave function is reflected and remains in the original subspace. We show that by normalizing the small bits of arriving (removed) norm, an ideal time distribution emerges in correspondence with a classical local-kinetic-energy distribution.
