Electromagnetic shielding in quantum metrology

Abstract

The dynamics of the quantum Fisher information of the parameters of the initial atomic state and atomic transition frequency is studied, in the framework of open quantum systems, for a static polarizable two-level atom coupled in the multipolar scheme to a bath of fluctuating vacuum electromagnetic fields without and with the presence of a reflecting boundary. Our results show that in the case without a boundary, the electromagnetic vacuum fluctuations always cause the quantum Fisher information of the initial parameters and thus the precision limit of parameter estimation to decrease. Remarkably, however, with the presence of a boundary, the quantum Fisher information becomes position and atomic polarization dependent, and as a result, it may be enhanced as compared to that in the case without a boundary and may even be shielded from the influence of the vacuum fluctuations in certain circumstances as if it were a closed system.

Probing the exotic structure of 8B by its elastic scattering and breakup reaction on nuclear targets

“…The results given in Fig. 8 are obtained at the same energy of 36 MeV/nucleon as the longitudinal momentum distributions of 7 Be fragments in the breakup of 8 B on a carbon target have been measured [23]. It is worth noting that although there are no 7 Be+ 12 C and 8 B+ 12 C elastic scattering data available at this specific energy, the diffraction nuclear model developed in Ref.…”

“…In this subsection we perform calculations of the breakup cross sections of 8 B on the target nuclei 9 Be, 12 C, and 197 Au and compare our results with the available experimental data [22,23]. The densities of these nuclei needed to compute the OPs are taken from Ref.…”

“…Here we should mention also the results of the experiments at lower energies for the breakup of 8 B in the collisions with Be and Au targets at 41 MeV/nucleon (81 ± 4 and 62 ± 3 MeV/c FWHM for Be and Au targets, respectively) [22] and for C target at 36 MeV/nucleon [23] with FWHM 124 ± 17 and 92±7 MeV/c for the stripping and diffraction components, correspondingly. Indeed, these experimental results reflect the large spatial extension of the loosely bound proton in 8 B.…”

Information flow versus divisibility for qubit evolution

“…Along with these new developments, comes a serious challenge of controlling and understanding real life quantum systems, which are inherently open to the environment. This has resulted in drawing a lot of interest about open quantum systems in recent times [1][2][3][4][5][6][7]. The evolution of such systems is represented by a dynamical map, that is, a family of completely positive (CP) trace-preserving (TP) maps Λ t : B(H) → B(H) (t ≥ 0), where B(H) denotes a linear space of bounded operators acting on the system Hilbert space H (actually, in this paper we consider only finite dimensional case and hence B(H) coincides with all linear operators on H).…”

Divisibility and Information Flow Notions of Quantum Markovianity for Noninvertible Dynamical Maps

“…Quantum systems interacting with an environment [5,6] are of increasing relevance due to rapidly developing modern quantum technologies like quantum communication or quantum computation [7]. It turns out that recent experimental techniques allow us to go beyond standard Markovian approximations and observe new memory effects caused by the environmental interaction [8][9][10]. Therefore, there is a need for the exploration of non-Markovian regime, and characterizing the genuine properties of this kind of evolution.…”