Search

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)

Four novel bis(heterocyclic) sequences, which incorporate a 2,2′-bipyridine system with the 2,2′-bithiazole, 4,4′-bithiazole, 2,2′-bipyrazine or 4,4′-bipyrimidine units, have been synthesized. In the presence of stoichiometric amounts of CuI, AgI or ZnII cations, fully oriented discrete head-to-head (H-H) or head-to-tail (H-T) species have been observed by NMR and X-ray crystallography. The orientation of the ligands in the AgI, CuI or Zn II dinuclear complexes during the self-assembly process appears to be under the control of electronic factors relating to the electronic configuration of the different bis(heterocyclic) sequences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Les noms de Pierre Schaeffer ou Pierre Boulez evoquent la vie musicale de l'apres 1945 en France. Mais la facon dont s'affirme cette « avant-garde atonale » dans les annees 1950 constitue l'un des aspects les plus obscurs de la vie culturelle de la Quatrieme Republique. Ce coin du voile est leve ici. Depassant une lecture exclusivement musicologique, l'analyse croise les domaines politique et musical pour interroger les strategies d'affirmation et de rupture de ces jeunes musiciens dans leur champ de competences.

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.

In this paper new aspects on the self-assembly processes of didentate coordinating ligands leading to a double-stranded helicate are described. It was reported, that directionality in the self-recognition of CuI ions could be driven by factors relating to the electronic configuration of heterocycles in carefully designed heterotopic ligands. If the sequential bipyrazine−bipyridine ligand strand 4 reacts with 1 equiv. of CuI the dimetallic complex [Cu2(L4)2][PF6]2 is formed in a cooperative process. In this coordination compound the two strands are oriented in opposite directions (HT) as illustrated by the X-ray structure of [Cu2(L4)2][PF6]2. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Various heterocycles have been introduced on the 3-picoline nucleus via a regioselective BuLi-Me2N(CH2)2OLi (BuLi-LiDMAE) mediated para-lithiation. Useful methyl-polyheterocycles were efficiently prepared by a one-pot lithiation–stannylation-Stille coupling sequence.

Various heterocycles have been introduced on the 3-picoline nucleus via a regioselective BuLi-Me2N(CH2)2OLi (BuLi-LiDMAE) mediated para-lithiation. Useful methyl-polyheterocycles were efficiently prepared by a one-pot lithiation–stannylation-Stille coupling sequence.

The Stille-type cross-coupling reaction on mesylate, tosylate, and triflate allowed synthesis of symmetrical but also interesting unsymmetrical monofunctionalized 2′2′-bipyridines in possible multigram scales.

The determination of the initial deprotonation site of 2-chloro- and 2-methoxypyridine during reaction with BuLi-LiDMAE has been investigated. A series of experiments on deuterated regioisomers revealed a direct lithiation at C-6 excluding a potential first classical ortholithiation and lithium equilibration in the reaction medium. These results suggested that the formation of lithium aggregates at the neighboring of the pyridinic nitrogen atom favored BuLi delivery at C-6 as well as 6-lithio intermediate stabilization.

Julien MATHIEU Un mythe fondateur de la musique contemporaine: le «scandale» provoque par la creation de Desertsd’Edgar Varese, le 2 decembre 1954 Le deux decembre 1954 a Paris, au Theâtre des Champs-Elysees, etait creee, dans le cadre de la programmation musicale de la R.T.F., une œuvre d’un compositeur alors tres peu connu en France,Deserts d’Edgar Varese.Le compositeur y developpait une esthetique marquee par la volonte d’inte~grer a la musique occidentale des sons jus~qu’alors refoules (percussions,bruits d’usines, etc...). Or, la presence de tels sons dans un cadre tres institutionnalise et codifie, provo~qua des reactions violentes de la part du public present. A partir de sources variees, issues notamment des fonds de la R.T.F. (archives ecrites,fonds sonores et televisuels), on cherchera a mieux saisir ce scandale, en privilegiant une approche micro-historique nous permettant d’analyser les raisons qui pousserent certains a faire comprendre au compositeur que sa musique, par son carac~tere d’etrangete, n’etait pas «a sa place». Ceci nous permettra d’eclairer la posterite du scan~dale qui, si elle fut peu importante dans l’opi~nion, fut plus determinante pour les compositeurs contemporains, qui firent de l’evenement une sorte de «bataille heroique» de la creation artistique moderne, instrumen~talisant ainsi la transgression, erigee en norme.

International audience

BuLi–Me2N(CH2)2OLi (BuLi–LiDMAE) promoted the clean C-6 functionalisation of 3-picoline via a methyl to C-6 lithium shift.