ABSTRACT
The integration of semiconductor Josephson junctions (JJs) in superconducting quantum circuits provides a versatile platform for hybrid qubits and offers a powerful way to probe exotic quasiparticle excitations. Recent proposals for using circuit quantum electrodynamics (cQED) to detect topological superconductivity motivate the integration of novel topological materials in such circuits. Here, we report on the realization of superconducting transmon qubits implemented with (Bi0.06Sb0.94)2Te3 topological insulator (TI) JJs using ultrahigh vacuum fabrication techniques. Microwave losses on our substrates, which host monolithically integrated hardmasks used for the selective area growth of TI nanostructures, imply microsecond limits to relaxation times and, thus, their compatibility with strong-coupling cQED. We use the cavity-qubit interaction to show that the Josephson energy of TI-based transmons scales with their JJ dimensions and demonstrate qubit control as well as temporal quantum coherence. Our results pave the way for advanced investigations of topological materials in both novel Josephson and topological qubits.
ABSTRACT
We establish a testbed system for the development of high-sensitivity Electron Spin Resonance (ESR) techniques for small samples at cryogenic temperatures. Our system consists of a NbN thin-film planar superconducting microresonator designed to have a concentrated mode volume to couple to a small amount of paramagnetic material, and to be resilient to magnetic fields of up to 400mT. At 65mK we measure high-cooperativity coupling (C≈19) to an organic radical microcrystal containing 1012 spins in a pico-litre volume. We detect the spin-lattice decoherence rate via the dispersive frequency shift of the resonator. Techniques such as these could be suitable for applications in quantum information as well as for pulsed ESR interrogation of very few spins to provide insights into the surface chemistry of, for example, the material defects in superconducting quantum processors.
ABSTRACT
Neuroscience, including research on Alzheimer's disease, is hampered by the lack of suitable in vitro models to study the human nervous system. To counteract this, many attempts to differentiate cell lines into more neuron-like cells have been performed, resulting in partial expression of neuronal features. Furthermore, it has been reported that neuroblastoma cell lines lack mature isoforms of tau. Our aim was to develop an improved in vitro model, generating sustainable cells with morphology and biochemistry of human, mature neurons. To obtain cells with neuronal differentiation and function, we investigated the effect of combining three-dimensional culturing of SH-SY5Y cells in extracellular matrix (ECM) gel with several factors reported to have neuro-differentiating effects. This resulted in cells with apparent neuronal morphology with long, extensively branched neurites. Further investigation revealed expression of several neurospecific markers including synapse protein Sv2 and nuclear marker NeuN, as well as the presence of synapses and axonal vesicle transport. In addition, these cells expressed mature tau isoforms, and tau protein expression was significantly increased compared to undifferentiated cells, reaching levels found in adult human brain. In conclusion, we found that pre-treatment with retinoic acid followed by ECM gel culturing in combination with brain derived neurotrophic factor, neuregulin beta1, nerve growth factor, and vitamin D3 treatment generated sustainable cells with unambiguous resemblance to adult neurons. These cells also expresses adult splicing forms of tau with neuronal localization, making this cellular in vitro model useful in many areas of neuroscience research, particularly the Alzheimer's disease field.
Subject(s)
Cell Differentiation/physiology , Neurons/physiology , Neurosciences/methods , Alzheimer Disease/pathology , Antigens, Nuclear/metabolism , Blotting, Western , Cell Line, Tumor , Cholecalciferol/pharmacology , Extracellular Matrix/metabolism , Humans , Immunohistochemistry , Microscopy, Fluorescence , Models, Neurological , Nerve Growth Factors/pharmacology , Nerve Tissue Proteins/biosynthesis , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Neurons/ultrastructure , Phosphorylation , Reverse Transcriptase Polymerase Chain Reaction , Synapses/metabolism , Synapses/ultrastructure , Vitamins/pharmacology , tau Proteins/biosynthesisABSTRACT
Here we present the direct observation of macroscopic quantum properties in an all high-critical-temperature superconductor d-wave Josephson junction. Although dissipation caused by low-energy excitations is expected to strongly suppress macroscopic quantum effects, we demonstrate energy level quantization in our d-wave Josephson junction. The result indicates that the role of dissipation mechanisms in high-temperature superconductors has to be revised, and it may also have consequences for the class of solid-state "quiet" quantum bits with superior coherence time.