122 research outputs found

    Molecular prototypes for spin-based CNOT quantum gates

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    We show that a chemically engineered structural asymmetry in [Tb2] molecular clusters renders the two weakly coupled Tb3+ spin qubits magnetically inequivalent. The magnetic energy level spectrum of these molecules meets then all conditions needed to realize a universal CNOT quantum gate.Comment: 4 pages, 4 figure

    Photoactivation of the cytotoxic properties of platinum(II) complexes through ligand photoswitching

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    The development of photoactivatable metal complexes with potential anticancer properties is a topical area of current investigation. Photoactivated chemotherapy using coordination compounds is typically based on photochemical processes occurring at the metal center. In the present study, an innovative approach is applied that takes advantage of the remarkable photochemical properties of diarylethenes. Following a proof-of-concept study with two complexes, namely, C1 and C2, a series of additional platinum(II) complexes from dithienylcyclopentene-based ligands was designed and prepared. Like C1 and C2, these new coordination compounds exhibit two thermally stable, interconvertible photoisomers that display distinct properties. The photochemical behavior of ligands L3-L7 has been analyzed by 1H NMR and UV-vis spectroscopies. Subsequently, the corresponding platinum(II) complexes C3-C7 were synthesized and fully characterized, including by single-crystal X-ray diffraction for some of them. Next, the interaction of each photoisomer (i.e., containing the open or closed ligand) of the metal complexes with DNA was examined thoroughly using various techniques, revealing their distinct DNA-binding modes and affinities, as observed for the earlier compounds C1 and C2. The antiproliferative activity of the two forms of the complexes was then assessed with five cancer cell lines and compared with that of C1 and C2, which supported the use of such diarylethene-based systems for the generation of a new class of potential photochemotherapeutic metallodrugs

    A heterometallic [LnLn′Ln] lanthanide complex as a qubit with embedded quantum error correction

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    We show that a [Er-Ce-Er] molecular trinuclear coordination compound is a promising platform to implement the three-qubit quantum error correction code protecting against pure dephasing, the most important error in magnetic molecules. We characterize it by preparing the [Lu-Ce-Lu] and [Er-La-Er] analogues, which contain only one of the two types of qubit, and by combining magnetometry, low-temperature specific heat and electron paramagnetic resonance measurements on both the elementary constituents and the trimer. Using the resulting parameters, we demonstrate by numerical simulations that the proposed molecular device can efficiently suppress pure dephasing of the spin qubits

    NMR Experiments on Rotating Superfluid 3He-A : Evidence for Vorticity

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    Experiments on rotating superfluid 3He-A in an open cylindrical geometry show a change in the NMR line shape as a result of rotation: The amplitude of the peak decreases in proportion to f(T)g(Ω), where Ω is the angular velocity of rotation; at the same time the line broadens. Near Tc, f(T) is a linear function of 1−T/Tc. At small velocities g(Ω)∝Ω. These observations are consistent with the existence of vortices in rotating 3He-A.Peer reviewe

    Control of Pressurized Superfluid Helium-II: Application to Loss Analysis

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    Dispositif cryogénique pour mesures magnétiques entre 4 et 300°K

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    The sample is cooled by a flow of helium gas from a liquid helium container.L'échantillon est refroidi par un courant d'hélium gazeux obtenu par pompage sur une bouteille d'hélium liquide

    Nuclear antiferromagnetism in lithium hydride

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    A nuclear antiferromagnetic structure has been produced in lithium hydride (LiH) by the usual method : 1) Dynamic nuclear polarization in high field (5.5 T); 2) Adiabatic demagnetization in the rotating frame. A dilution refrigerator of special design has been built for the particular features of the experiment. The ordered state persists for more than one hour after the demagnetization. Three types of evidence have been obtained experimentally by NMR on the ordered structures : 1) Shape of the dipolar absorption line of the 7Li nuclear spins; 2) Behaviour of the perpendicular susceptibility of these spins as a function of dipolar energy; 3) Splitting of the Zeeman absorption line of the 6Li nuclear spins. Following these results, a neutron diffraction study of LiH has been undertaken and has already yielded some results.L'antiferromagnétisme nucléaire a été créé dans l'hydrure de lithium (LiH) par la méthode désormais usuelle : 1) Polarisation dynamique nucléaire, dans un champ de 5,5 T ; 2) Désaimantation adiabatique dans le référentiel tournant. Un réfrigérateur à dilution d'un type spécial a été construit, pour obéir aux contraintes particulières de l'expérience. L'état ordonné subsiste plus d'une heure après la désaimantation. On a obtenu par RMN trois types d'évidences expérimentales de la structure ordonnée : 1) Forme de la raie d'absorption dipolaire des spins nucléaires de 7Li; 2) Comportement de la susceptibilité perpendiculaire de ces spins en fonction de l'énergie dipolaire; 3) Dédoublement de la raie d'absorption Zeeman des spins nucléaires de 6Li. A la lumière de ces résultats a été entreprise une étude de LiH par diffraction de neutrons, qui a porté ses premiers résultats

    Cryostat à température réglable entre 4° et 300 °K et mesure de la conductibilité thermique

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    We describe a cryostat the temperature of which can be continuously varied from 4° to 300 °K and working by forced circulation of helium gas. The higher the temperature, the less is the consumption. This apparatus is used for measuring the thermal conductivity of germanium and silicon single crystals. The measuring technique is described in detail.On décrit un cryostat à température ajustable entre 4° et 300 °K fonctionnant par circulation forcée d'hélium gazeux et dont la consommation est d'autant plus faible que la température est plus élevée. L'appareil est utilisé à la mesure de la conductibilité thermique K de monocristaux de germanium et de silicium. La technique de mesure est décrite en détail
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