Through the combination of three different, complementary techniques (optical microscopy, x-ray diffraction and atomic force microscopy), we reveal the deformations inside thin smectic films frustrated between two interfaces imposing antagonistic anchorings. We study the model system, 4-n-octyl-4'-cyanobiphenyl (8CB) between MoS2 and air, which is characterized by the competition between homeotropic anchoring at air and planar unidirectional anchoring on the substrate, with thicknesses varying around 0.3 microm. Optical microscopy and x-ray diffraction demonstrate the continuous topology of smectic layers between the interfaces, which are stacked into periodic flattened hemicylinders. These latter are one-dimensional (1D) focal conic domains which form an optical grating in the smectic film, of a period ranging from 1 to 2.5 microm. The interpretation of our results through an energetic model, associated with the atomic force microscopy (AFM) measurements, shows the presence below a critical thickness of a new type of curvature wall between neighboring hemicylinders.
Molecular spin qubits have been shown to reach sufficiently long quantum coherence times to envision their use as hardware in quantum processors. These will however require their implementation in hybrid solid-state devices for which the controlled localization and homogeneous orientation of the molecular qubits will be necessary. An alternative to isolated molecules that can ensure these key aspects is 2D framework in which the qubit would act as node. In this work, it is demonstrated that the isolated metalloporphyrin [Cu(H 4 TCPP)] molecule is a potential spin qubit, and maintains similar quantum coherence as node in a 2D [{CuTCPP}Zn 2 (H 2 O) 2 ] metal-organic framework. Mono-and multilayer deposits of nanosheets of a similar 2D framework are then successfully formed following a modular method based on Langmuir-Schaefer conditions. The orientation of the {CuTCPP} qubit nodes in these nanosheets is homogeneous parallel to the substrate. These nanosheets are also formed with a control over the qubit concentration, i.e., by dilution with the unmetallated porphyrin. Eventually, 2D nanosheets are formed in situ directly on a substrate, through a simple protocol devised to reproduce the Langmuir-Schaefer conditions locally. Altogether these studies show that 2D spin qubit frameworks are ideal components to develop a hybrid quantum computing architecture. and gates first arose in the form of purely organic systems, using either the multiple nuclear spins of rationally selected molecules or the electronic spin(s) of open shell organic molecules bearing one or multiple radicals. The careful design and selection of such organic molecules coupled to sophisticated experiments have allowed implementing realistic quantum operations using ensembles of these. [2] Paramagnetic coordination complexes were later proposed as alternative molecular spin qubits, after it was argued and shown that the molecule electronic spin orientation and quantum superpositions allow to encode quantum bit (qubit) states. [3] Recent improvements in the coherence times of these molecular spin qubits [4] and the unique ability to design molecules with multiple qubits as prototypes of quantum gates [5] have brought this scheme to a point where it becomes reasonable to envision the design of a magnetic quantum processor. A magnetic molecule has even recently been used to implement Grover's quantum algorithm, albeit using its metal ion nuclear spin. [6] One of the advantages of the molecular scheme is that macroscopic numbers of identical qubits are obtained in one sole reaction. While this is appealing for the daunting challenge of scaling to a usable size, common to all proposed schemes, [7] the technology to build a scalable quantum architecture based on molecular qubits is
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