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We study very generally towhat extent the uncertainty with which a phase shift can be estimated in quantum metrology can be reduced by extending the Hamiltonian that generates the phase shift to an ancilla system with a Hilbert space of arbitrary dimension, and allowing arbitrary interactions between the original system and the ancilla. Such Hamiltonian extensions provide a general framework for open quantum systems, as well as for “non-linear metrology schemes” that have been investigated over the last few years. We prove that such Hamiltonian extensions cannot improve the sensitivity of the phase shift measurement when considering the quantum Fisher information optimized over input states.

A well-studied scenario in quantum parameter estimation theory arises when the parameter to be estimated is imprinted on the initial state by a Hamiltonian of the form $\theta G$. For such "phase shift Hamiltonians" it has been shown that one cannot improve the channel quantum Fisher information by adding ancillas and letting the system interact with them. Here we investigate the general case, where the Hamiltonian is not necessarily a phase shift, and show that in this case in general it \emph{is} possible to increase the quantum channel information and to reach an upper bound. This can be done by adding a term proportional to the derivative of the Hamiltonian, or by subtracting a term to the original Hamiltonian. Both methods do not make use of any ancillas and show therefore that for quantum channel estimation with arbitrary parameter-dependent Hamiltonian, entanglement with an ancillary system is not necessary to reach the best possible sensitivity. By adding an operator to the Hamiltonian we can also modify the time scaling of the channel quantum Fisher information. We illustrate our techniques with NV-center magnetometry and the estimation of the direction of a magnetic field in a given plane using a single spin-1 as probe., Comment: New references included

We consider quantum channel-estimation for depolarizing channels and phase-flip channels extended by ancilla qubits and fed with a GHZ orWstate. After application of the channel one or several qubits can be lost, and we calculate the impact of the loss on the quantum Fisher information that determines the smallest uncertainty with which the parameters of these channels can be estimated.

A new discrete supramolecular pseudo-helicate has been obtained from a saturated heterotopic methylbipyrazyl–methylbipyridyl ligand strand and NiCl2. The X-ray structure of the dinuclear complex shows the 2-oxapropylene bridge oxygen atoms are engaged in coordination to the octahedral metal centre and a selective ligand inter-strand orientation is promoted in the complex. The crystal packing shows a perfect regular linear arrangement of the asymmetric units giving a packing of interacting molecules having well-defined rectangular and polygonal open channels. Although a paramagnetic behaviour is observed above 10 K, below this temperature a significant deviation of this behaviour suggests the presence of an NiII–NiII magnetic coupling. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

At the southern side of the Anti- Atlas mountains, the lower section of the Assaka wadi valley joins the Atlantic ocean by crossing an Appalachian basin and range area Holocene deposits of the lower section of the Assaka wadi show two main sedimentary formations the upper sheet-fans and the lower terraces. The upper sheet-fans are probably from the lower Rharbian (Holocene) age, they are located above the Soltanian (Wurmian) formations at the outlets of tributaries. They consist of accumulations with silts, aeolian quartz and high palygorskite contents. After this penod, a trench cut through the older formations took place between 8 000 years BP and 4 200 years BP. The lower over terraces, 5 to 11 metres thick, are inset in the trench cut through the Soltanian formations and show four superimposed and fining upwards (from pebble to silt) cross-bedded units. This study shows many geodynamic and palaeoclimatic conditions Lower Rharbian fans indicate that the climate was sufficiently and to denude the slopes, where, during big storms, gullies and run-off supplied the Assaka wadi with silts and sands. Torrential floods cut the Soltanian formations and then created the Middle Rharbian low terrace Finally, the Historic terrace, superimposed onto the Middle Rharbian one, shows that important flood events took place during the XVII0 and XVIII° centuries, but nevertheless with low frequency However, this sequence indicates wetter conditions during an and episode. The 14C age is contemporary with the "cold winters" in Western Europe ; this fact proves that the synoptic conditions in South Morocco were the same at 280±30 years B.P. as at present., L'oued Assaka, exutoire d'un vaste bassin versant (7 000 km2) rejoint l'océan Atlantique sur le versant sud de l' Anti-Atlas en recoupant une zone de relief appalachien. Des cônes attnbuables au Pléistocène supérieur ou au Rharbien ancien (Holocène ancien) surmontent les formations alluviales et colluviales soltaniennes (Wurm), avant que celles-ci soient entaillées sur 20 à 25 mètres , ils sont circonscrits aux débouches des foums que déterminent les affluents de l'oued Assaka. Ils sont constitués de limons sableux riches en grains de quartz éohsés et par des teneurs en palygorskite qui s'accentuent de la base vers le sommet. Aux environs de 8 000 BP, une phase d'incision linéaire importante entailla les dépôts plus anciens sur une épaisseur de 20 mètres. De basses terrasses sont emboîtées dans les dépôts soltaniens. D'une épaisseur vanant de 5 à 1 1 mètres, elles sont constituées de séquences granoclassées qui mettent en évidence des géodynamiques et des ambiances climatiques contrastées. Le Rharbien ancien reflète une sécheresse suffisante pour dénuder en partie les versants, qui lors d'orages probablement assez localisés, alimentent les affluents de l'oued principal en limons sableux. Les crues torrentielles (chaînant des blocs surdimensionnés) ont incisé les formations soltaniennes -essentiellement limoneuses- et ont mis en place les basses terrasses du Rharbien moyen. Enfin, la terrasse historique étagée sur celle du Rharbien moyen montre la permanence de crues importantes durant les XVIIème et XVIIIème siècles avec une fréquence cependant moins élevée. En outre, cette séquence indique l'existence de conditions humides durant un épisode aride sous cette latitude contemporaines des "hivers froids" de l'Europe de l'Ouest ; ce qui prouve que les situations synoptiques dans le Sud du Maroc étaient les mêmes à 280±30 ans BP qu'aujourd'hui., Mathieu Julien, Weisrock André, Wengler Luc, Brochier Jacques-Élie, Even Georges, Fontugne Michel, Mercier Norbert, Ouammou Abderrahman, Sénégas Franck, Valladas Hélène, Vernet Jean Louis, Wahl Laurent. The pleistocene alluvial formations of the Loir river in the Vendôme region (Loir-et-Cher, France) morphosedimentary context and ESR chronology [Les dépôts holocènes de la basse vallée de l'Oued Assaka, Sud-Maroc : résultats préliminaires.]. In: Quaternaire, vol. 15, n°1-2, 2004. Fluvial Archives Group. Clermond-Ferrant 2002. pp. 207-218.

The Wadi Assaka drains a large watershed on the southwest border of Anti-Atlas and its Saharan edges in the Guelmim area. It crosses the last folded chains of the Anti- Atlas before flowing into the Atlantic Ocean. In this part of its course, it aggraded a large system of alluvial terraces. The oldest of them are stepped terraces, the last ones are inset terraces. One of them is particularly interesting by its thickness, its various deposits as well as their content. The whole formation is now deeply cut, so the different sedimentary faciès can be observed and it is possible to reconstruct the palaeoenvironments, the ancient dynamics of the river and to connect the deposits with the regional and general climatic evolution. This stratigraphy has seemingly recorded rapid climatic events with a high resolution during the isotopic stages 5 to 2 It gives reference points about the way the African continent responded to global climatic changes between the Mediterranean and Saharan areas., L'oued Assaka draîne un important bassin versant sur la bordure sud de l'Anti-Atlas occidental et ses marges sahariennes dans la région de Guelmim. Il traverse les derniers chaînons anti-atlasiques plissés avant de déboucher dans l'océan Atlantique. Dans cette partie de son cours, il a édifié un système de terrasses alluviales étagées pour les plus anciennes et emboîtées pour les dernières. L'une d'entre elles est particulièrement remarquable à la fois par sa puissance, la variété de ses dépôts, ainsi que par leur contenu. Les divers faciès sédimentaires visibles grâce à une forte incision linéaire actuelle qui recoupe l'ensemble de la formation permettent de reconstituer les paléoenvironnements, la dynamique passée de l'oued et de proposer une interprétation des dépôts en relation avec l'évolution climatique régionale et globale. Cette séquence sédimentaire paraît avoir enregistré en haute résolution des événements climatiques rapides durant les stades isotopiques 5 à 2. Elle fournit des repères concernant la réponse du continent africain face aux changements climatiques globaux à la frontière des domaines méditerranéen et saharien., Wengler Luc, Weisrock André, Brochier-do not use Jacques-Élie, Brugal Jean Philippe, Fontugne Michel, Magnin Frédéric, Mathieu Julien, Mercier Norbert, Ouammou Abderrahman, Reyss Jean-Louis, Sénégas Franck, Valladas Hélène, Wahl Laurent. Enregistrement fluviatile et paléoenvironnements au Pléistocène supérieur sur la bordure méridionale atlantique de l'Anti-Atlas (Oued Assaka, S-O marocain). In: Quaternaire, vol. 13, n°3-4, 2002. Événements rapides, instabilités, changements culturels au Quaternaire. pp. 179-192.