We consider the problem of characterising the spatial extent of a composite light source using the superresolution imaging technique when the centroid of the source is not known precisely. We show that the essential features of this problem can be mapped onto a simple qubit model for joint estimation of a phase shift and a dephasing strength.
To perform efficient many-body calculations in the framework of the exact diagonalization of the Hamiltonian one needs an appropriately tailored Fock basis built from the single-particle orbitals. The simplest way to compose the basis is to choose a finite set of single-particle wave functions and find all possible distributions of a given number of particles in these states. It is known, however, that this construction leads to very inaccurate results since it does not take into account different many-body states having the same energy on equal footing. Here we present a fast and surprisingly simple algorithm for generating the many-body Fock basis build from many-body Fock states having the lowest non-interacting energies. The algorithm is insensitive to details of the distribution of single-particle energies and it can be used for an arbitrary number of particles obeying bosonic or fermionic statistics. Moreover, it can be easily generalized to a larger number of components. Taking as a simple example the system of two ultra-cold bosons in an anharmonic trap, we show that exact calculations in the basis generated with the algorithm are substantially more accurate than calculations performed within the standard approach.
Intracavity laser absorption spectroscopy was used to measure the number density of neutral ground state barium atoms desorbed from an operating dispenser cathode. The measurement suggests an order of magnitude value of 10' atoms/cm3 at a distance of 5 cm from the emitting surface. This is the first direct state selective measurement of the barium density near to the surface of an operating cathode which can be directly traced to conventional multipass absorption spectroscopy. The value we obtain is consistent --with results reported by other workers using less direct methods-and allows more detailed statements to be made concerning the chemical state of the Ba at the instant of desorption.[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 131.193.242.166 On: Tue, 02 Dec 2014 03:53:32 FIG; 6. Schematic diagram of spatial pattern of barium desorption from cathode showing intersection with laser beam. 2817
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