Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

One fundamental requirement for quantum computation is to perform universal manipulations of quantum bits at rates much faster than the qubit's rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here we show that by subjecting each electron spin to a magnetic field of different magnitude we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic field gradient of several hundred milliTesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single and potentially multiple qubit operations with gate times that approach the threshold required for quantum error correction.Comment: 11 pages, 4 figures. Supplementary Material included as ancillary fil

Quantum control of proximal spins using nanoscale magnetic resonance imaging

Quantum control of individual spins in condensed matter systems is an emerging field with wide-ranging applications in spintronics, quantum computation, and sensitive magnetometry. Recent experiments have demonstrated the ability to address and manipulate single electron spins through either optical or electrical techniques. However, it is a challenge to extend individual spin control to nanoscale multi-electron systems, as individual spins are often irresolvable with existing methods. Here we demonstrate that coherent individual spin control can be achieved with few-nm resolution for proximal electron spins by performing single-spin magnetic resonance imaging (MRI), which is realized via a scanning magnetic field gradient that is both strong enough to achieve nanometric spatial resolution and sufficiently stable for coherent spin manipulations. We apply this scanning field-gradient MRI technique to electronic spins in nitrogen-vacancy (NV) centers in diamond and achieve nanometric resolution in imaging, characterization, and manipulation of individual spins. For NV centers, our results in individual spin control demonstrate an improvement of nearly two orders of magnitude in spatial resolution compared to conventional optical diffraction-limited techniques. This scanning-field-gradient microscope enables a wide range of applications including materials characterization, spin entanglement, and nanoscale magnetometry.Comment: 7 pages, 4 figure

High resolution nuclear magnetic resonance spectroscopy of highly-strained quantum dot nanostructures

Much new solid state technology for single-photon sources, detectors, photovoltaics and quantum computation relies on the fabrication of strained semiconductor nanostructures. Successful development of these devices depends strongly on techniques allowing structural analysis on the nanometer scale. However, commonly used microscopy methods are destructive, leading to the loss of the important link between the obtained structural information and the electronic and optical properties of the device. Alternative non-invasive techniques such as optically detected nuclear magnetic resonance (ODNMR) so far proved difficult in semiconductor nano-structures due to significant strain-induced quadrupole broadening of the NMR spectra. Here, we develop new high sensitivity techniques that move ODNMR to a new regime, allowing high resolution spectroscopy of as few as 100000 quadrupole nuclear spins. By applying these techniques to individual strained self-assembled quantum dots, we measure strain distribution and chemical composition in the volume occupied by the confined electron. Furthermore, strain-induced spectral broadening is found to lead to suppression of nuclear spin magnetization fluctuations thus extending spin coherence times. The new ODNMR methods have potential to be applied for non-invasive investigations of a wide range of materials beyond single nano-structures, as well as address the task of understanding and control of nuclear spins on the nanoscale, one of the central problems in quantum information processing

Spin Relaxation in Ge/Si Core-Shell Nanowire Qubits

Controlling decoherence is the most challenging task in realizing quantum information hardware. Single electron spins in gallium arsenide are a leading candidate among solid- state implementations, however strong coupling to nuclear spins in the substrate hinders this approach. To realize spin qubits in a nuclear-spin-free system, intensive studies based on group-IV semiconductor are being pursued. In this case, the challenge is primarily control of materials and interfaces, and device nanofabrication. We report important steps toward implementing spin qubits in a predominantly nuclear-spin-free system by demonstrating state preparation, pulsed gate control, and charge-sensing spin readout of confined hole spins in a one-dimensional Ge/Si nanowire. With fast gating, we measure T1 spin relaxation times in coupled quantum dots approaching 1 ms, increasing with lower magnetic field, consistent with a spin-orbit mechanism that is usually masked by hyperfine contributions

Intracellular Trafficking of the Amyloid β-Protein Precursor (APP) Regulated by Novel Function of X11-Like

Background: Amyloid beta (A beta), a causative peptide of Alzheimer's disease, is generated by intracellular metabolism of amyloid beta-protein precursor (APP). In general, mature APP (mAPP, N- and O-glycosylated form) is subject to successive cleavages by alpha- or beta-, and gamma-secretases in the late protein secretory pathway and/or at plasma membrane, while immature APP (imAPP, N-glycosylated form) locates in the early secretory pathway such as endoplasmic reticulum or cis-Golgi, in which imAPP is not subject to metabolic cleavages. X11-like (X11L) is a neural adaptor protein composed of a phosphotyrosine-binding (PTB) and two C-terminal PDZ domains. X11L suppresses amyloidogenic cleavage of mAPP by direct binding of X11L through its PTB domain, thereby generation of A beta lowers. X11L expresses another function in the regulation of intracellular APP trafficking. Methodology: In order to analyze novel function of X11L in intracellular trafficking of APP, we performed a functional dissection of X11L. Using cells expressing various domain-deleted X11L mutants, intracellular APP trafficking was examined along with analysis of APP metabolism including maturation (O-glycosylation), processing and localization of APP. Conclusions: X11L accumulates imAPP into the early secretory pathway by mediation of its C-terminal PDZ domains, without being bound to imAPP directly. With this novel function, X11L suppresses overall APP metabolism and results in further suppression of Ab generation. Interestingly some of the accumulated imAPP in the early secretory pathway are likely to appear on plasma membrane by unidentified mechanism. Trafficking of imAPP to plasma membrane is observed in other X11 family proteins, X11 and X11L2, but not in other APP-binding partners such as FE65 and JIP1. It is herein clear that respective functional domains of X11L regulate APP metabolism at multiple steps in intracellular protein secretory pathways

Severe distortion of an orbital titanium mesh implant after recurrent facial trauma: a potential threat to the orbital contents?

Titanium mesh implants have proved their effectiveness in the reconstruction of fractures of the orbital wall, and their compromise between stiffness and elasticity allows for optimal support of the orbital contents. However, after recurrent orbital trauma, these implants (even when properly positioned) can become a potential "penetrating object" that threatens the critical adjacent anatomical structures. We report the case of a patient with recurrent facial trauma whose orbit had previously been reconstructed with a titanium implant, and which resulted in severe deformation

Reconstitution bicorticale de grande taille de l’os calvarial par ciment ostéoconducteur Hydroset® associé à une grille en titane. Étude préliminaire

International audienceSummaryIntroductionBi-cortical calvarial bone loss is a very frequent issue for neurosurgery and craniofacial surgery. Several techniques can be used to reconstruct the skull, with variable difficulty and costs. The purpose of our study was to assess the use of Hydroset® osteoconductive cement for large size bicortical cranioplasties.Materials and methodsThree patients presented with extensive loss of calvarial bone bi-cortical substance (> 25 cm2), between 2010 and 2012. The 3 patients underwent cranioplasty with Hydroset® osteoconductive cement and titanium mesh.ResultsThe esthetic results were very satisfactory, especially for the skull dome, with a completely invisible and non-palpable cement/native skull junction. Scalp adherence to the cement was natural with maintenance of skin mobility.DiscussionBicortical calvarial bone reconstruction with Hydroset® cement is technically easy to perform, gives very good results, with an uneventful outcome, and induces lower costs.IntroductionLes pertes de substance bicorticales de l’os calvarial sont un problème fréquemment rencontré en neurochirurgie et en chirurgie craniofaciale. Plusieurs techniques existent afin de reconstruire le crâne, avec des difficultés de réalisation et des coûts variables. Le but de cette étude préliminaire est de voir si le ciment ostéoconducteur Hydroset® peut être utilisé pour des cranioplasties bicorticales de grandes tailles.Patients et méthodeEntre 2010 et 2012, trois patients ont présenté des pertes de substance bicorticales de grandes tailles (> 25 cm2) de l’os calvarial. Les 3 patients ont eu une cranioplastie par ciment ostéoconducteur Hydroset® associé à une grille en titane.RésultatsLes résultats esthétiques étaient très satisfaisants, en particulier sur le bombé du crâne et avec une jonction ciment/crâne natif parfaitement invisible et non palpable. L’adhérence du scalp à la cranioplastie en ciment était naturelle avec préservation d’un plan de glissement.DiscussionLa reconstruction bicorticale de l’os calvarial par ciment Hydroset® offre certains avantages sur le plan technique (facilité d’utilisation, très bons résultats, suites simples) et sur le plan économique

Mucoceles of the anterior ventral surface of the tongue and the glands of Blandin Nuhn: 5 cases

International audienceINTRODUCTION: Mucoceles are cystic diseases of the oral mucosa. The most common are ranula and mococeles of the lower lip. Blandin and Nuhn mucoceles, which develop at the ventral side of the tongue, are rare benign lesions. They are often misdiagnosed and sometimes confused with ranula. The recommended treatment is a complete surgical excision of the gland.PATIENTS AND METHODS: We describe 5 clinical cases managed in service between 2009 and 2016. Clinical cases are presented in order to detail their clinical history, paraclinical and treatment.RESULTS: The clinical appearance is a longitudinal swelling of the ventral surface of the tongue, parallel to the frenulum. The volume of the swelling is variable; it is normally around 30 x 10 mm. The paraclinical (ultrasound, CT, MRI, or ponction) could be performed. CT showed an cyst located on the ventral surface of the tongue, with liquid density. Blandin and Nunh mucocele were strictly anechogenic. MRI confirms the liquid content of this cyst (low T1signal, high T2signal and no postcontrast enhanced). The resection of Blandin and Nuhn glands should respect the sublingual gland, the lingual nerve and the lingual veins in the mouth floor.CONCLUSION: This study demonstrates that Blandin and Nuhn mucoceles must be understood and recognised to propose complete excision of the Blandin and Nuhn gland and avoid recurrence.Copyright © 2019. Published by Elsevier Masson SAS