arXiv subjects
Publications and source records attributed to M. Fortunato.
We show that conditional measurements on atoms following their interaction with a resonant cavity field mode can be used to effectively counter the decoherence of Fock-state superpositions due to cavity leakage.
We present a scheme for controlling the decoherence of a linear superposition of two coherent states with opposite phases in a high-Q microwave cavity, based on the injection of appropriately prepared ``probe'' and ``feedback'' Rydberg atoms, improving the one presented in [D. Vitali et al., Phys. Rev. Lett. 79, 2442 (1997)]. In the present scheme, the information transmission from the probe to the feedback atom is directly mediated by a second auxiliary cavity. The detection efficiency for the probe atom is no longer a critical parameter, and the decoherence time of the superposition state can be significantly increased using presently available technology.
By sending many two-level atoms through a cavity resonant with the atomic transition, and letting the interaction times between the atoms and the cavity be randomly distributed, we end up with a predetermined Fock state of the electromagnetic field inside the cavity if we perform after the interaction with the cavity a conditional measurement of the internal state of each atom in a coherent superposition of its ground and excited states. Differently from previous schemes, this procedure turns out to be very stable under fluctuations in the interaction times.
The evolution of a single mode of the electromagnetic field interacting with a squeezed bath in a Kerr medium is considered. The solution of the corresponding master equation is given numerically. It is argued that the creation of a superposition state (Schrödinger's cat) is better achieved in presence of a squeezed reservoir than of a thermal one.
A new master equation performing isotropic phase-number squeezing is suggested. The phase properties of coherent superpositions are analyzed when the state evolves in presence of a bath with fluctuations squeezed in this isotropic way. We find that such a reservoir greatly improves persistence of coherence with respect to either a customary thermal bath, or to an anisotropically squeezed phase-sensitive bath.