Read by QxMD icon Read

Quantum physics

Xun Gao, Lu-Ming Duan
Part of the challenge for quantum many-body problems comes from the difficulty of representing large-scale quantum states, which in general requires an exponentially large number of parameters. Neural networks provide a powerful tool to represent quantum many-body states. An important open question is what characterizes the representational power of deep and shallow neural networks, which is of fundamental interest due to the popularity of deep learning methods. Here, we give a proof that, assuming a widely believed computational complexity conjecture, a deep neural network can efficiently represent most physical states, including the ground states of many-body Hamiltonians and states generated by quantum dynamics, while a shallow network representation with a restricted Boltzmann machine cannot efficiently represent some of those states...
September 22, 2017: Nature Communications
Tomohiro Otsuka, Takashi Nakajima, Matthieu R Delbecq, Shinichi Amaha, Jun Yoneda, Kenta Takeda, Giles Allison, Peter Stano, Akito Noiri, Takumi Ito, Daniel Loss, Arne Ludwig, Andreas D Wieck, Seigo Tarucha
Understanding the dynamics of open quantum systems is important and challenging in basic physics and applications for quantum devices and quantum computing. Semiconductor quantum dots offer a good platform to explore the physics of open quantum systems because we can tune parameters including the coupling to the environment or leads. Here, we apply the fast single-shot measurement techniques from spin qubit experiments to explore the spin and charge dynamics due to tunnel coupling to a lead in a quantum dot-lead hybrid system...
September 22, 2017: Scientific Reports
Søren Brier
Charles S. Peirce developed a process philosophy featuring a non-theistic agapistic evolution from nothingness. It is an Eastern inspired alternative to the Western mechanical ontology of classical science also by the American transcendentalists. Advaitism and Buddhism are the two most important Eastern philosophical traditions that encompass scientific knowledge and the idea of spontaneous evolutionary development. This article attempts to show how Peirce's non-mechanical triadic semiotic process theory can embrace the quantum field view better than the mechanical and information views in a theory of the emergence of consciousness...
September 19, 2017: Progress in Biophysics and Molecular Biology
Cyrille Lavigne, Paul Brumer
Control of molecular processes via adaptive feedback often yields highly structured laser pulses that have eluded physical explanation. By contrast, coherent control approaches propose physically transparent mechanisms but are not readily visible in experimental results. Here, an analysis of a condensed phase adaptive feedback control experiment on retinal isomerization shows that it manifests a quantum interference based coherent control mechanism: control via interfering resonances. The result promises deep insight into the physical basis for the adaptive feedback control of a broad class of bound state processes...
September 21, 2017: Journal of Chemical Physics
Marissa L Weichman, Jessalyn A DeVine, Mark C Babin, Jun Li, Lifen Guo, Jianyi Ma, Hua Guo, Daniel M Neumark
The transition state governs how chemical bonds form and cleave during a chemical reaction and its direct characterization is a long-standing challenge in physical chemistry. Transition state spectroscopy experiments based on negative-ion photodetachment provide a direct probe of the vibrational structure and metastable resonances that are characteristic of the reactive surface. Dynamical resonances are extremely sensitive to the topography of the reactive surface and provide an exceptional point of comparison with theory...
October 2017: Nature Chemistry
Phitsini Suvarnaphaet, Suejit Pechprasarn
The advantages conferred by the physical, optical and electrochemical properties of graphene-based nanomaterials have contributed to the current variety of ultrasensitive and selective biosensor devices. In this review, we present the points of view on the intrinsic properties of graphene and its surface engineering concerned with the transduction mechanisms in biosensing applications. We explain practical synthesis techniques along with prospective properties of the graphene-based materials, which include the pristine graphene and functionalized graphene (i...
September 21, 2017: Sensors
Zhen Wang, Zhiming Liu, Chengkang Su, Biwen Yang, Xixi Fei, Yi Li, Yuqing Hou, Henan Zhao, Yanxian Guo, Zhengfei Zhuang, Huiqing Zhong, Zhouyi Guo
Ascribe to the unique two-dimensional planar nanostructure with exceptional physical and chemical properties, black phosphorous (BP) as the emerging inorganic two-dimensional nanomaterial with high biocompatibility and degradability has been becoming one of the most promising materials of great potentials in biomedicine. The exfoliated BP sheets possess ultra-high surface area available for valid bio-conjugation and molecular loading for chemotherapy. Utilizing the intrinsic near-infrared optical absorbance, BP-based photothermal therapy in vivo, photodynamic therapy and biomedical imaging has been realized, achieving unprecedented anti-tumor therapeutic efficacy in animal experiments...
September 20, 2017: Current Medicinal Chemistry
Pier Mario Biava, Fabio Burigana, Roberto Germano, Philip Kurian, Claudio Verzegnassi, Giuseppe Vitiello
A long history of research has pursued the use of embryonic factors isolated during cell differentiation processes for the express purpose of transforming cancer cells back to healthy phenotypes. Recent results have clarified that the substances present at different stages of cell differentiation-which we call stem cell differentiation stage factors (SCDSFs)-are proteins with low molecular weight and nucleic acids that regulate genomic expression. The present review summarizes how these substances, taken at different stages of cellular maturation, are able to retard proliferation of many human tumor cell lines and thereby reprogram cancer cells to healthy phenotypes...
September 20, 2017: Current Medicinal Chemistry
Chao Lei, Shijie Peng, Chenyong Ju, Man-Hong Yung, Jiangfeng Du
Quantum mechanical systems lose coherence through interacting with external environments-a process known as decoherence. Although decoherence is detrimental for most of the tasks in quantum information processing, a substantial degree of decoherence is crucial for boosting the efficiency of quantum processes, for example, in quantum biology and other open systems. The key to the success in simulating those open quantum systems is therefore the ability of controlling decoherence, instead of eliminating it. Motivated by simulating quantum open systems with Nitrogen-Vacancy centers, which has become an increasingly important platform for quantum information processing tasks, we developed a new set of steering pulse sequences for controlling various coherence times of Nitrogen-Vacancy centers; our method is based on a hybrid approach that exploits ingredients in both digital and analog quantum simulations to dynamically couple or decouple the system with the physical environment...
September 20, 2017: Scientific Reports
Richard H W Funk
This overview addresses phenomena in cell- and molecular biology which are puzzling by their fast and highly coordinated way of organization. Generally, it appears that informative processes probably involved are more on the biophysical than on the classical biochemical side. The coordination problem is explained within the first part of the review by the topic of endogenous electrical phenomena. These are found e.g. in fast tissue organization and reorganization processes like development, wound healing and regeneration...
January 1, 2018: Frontiers in Bioscience (Landmark Edition)
Khagendra Baral, Aize Li, Wai-Yim Ching
A density functional theory (DFT) based ab initio molecular dynamics (AIMD) has been applied to simulate models of single and mixed alkali silicate glasses with two different molar concentrations of alkali oxides. The structural environments and spatial distributions of alkali ions in the 10 simulated models with 20% and 30% of Li, Na, K and equal proportions of Li-Na and Na-K are studied in detail for subtle variations among the models. Quantum mechanical calculations of electronic structures, interatomic bonding, mechanical and optical properties are carried out for each of the models and the results are compared with available experimental observation and other simulations...
September 20, 2017: Journal of Physical Chemistry. A
Audrey Cottet, Matthieu C Dartiailh, Matthieu M Desjardins, Tino Cubaynes, Lauriane C Contamin, Matthieu Delbecq, Jérémie J Viennot, Laure E Bruhat, Benoit Douçot, Takis Kontos
Circuit QED techniques have been instrumental in manipulating and probing with exquisite sensitivity the quantum state of superconducting quantum bits coupled to microwave cavities. Recently, it has become possible to fabricate new devices in which the superconducting quantum bits are replaced by hybrid mesoscopic circuits combining nanoconductors and metallic reservoirs. This mesoscopic QED provides a new experimental playground to study the light-matter interaction in electronic circuits. Here, we present the experimental state of the art of mesoscopic QED and its theoretical description...
September 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Dario Ghersi, Abhishek Parakh, Mihaly Mezei
Four pseudorandom number generators were compared with a physical, quantum-based random number generator using the NIST suite of statistical tests, which only the quantum-based random number generator could successfully pass. We then measured the effect of the five random number generators on various calculated properties in different Markov-chain Monte Carlo simulations. Two types of systems were tested: conformational sampling of a small molecule in aqueous solution and liquid methanol under constant temperature and pressure...
September 18, 2017: Journal of Computational Chemistry
Wenyuan Liu, Andrea Nanetti, Siew Ann Cheong
Even as we advance the frontiers of physics knowledge, our understanding of how this knowledge evolves remains at the descriptive levels of Popper and Kuhn. Using the American Physical Society (APS) publications data sets, we ask in this paper how new knowledge is built upon old knowledge. We do so by constructing year-to-year bibliographic coupling networks, and identify in them validated communities that represent different research fields. We then visualize their evolutionary relationships in the form of alluvial diagrams, and show how they remain intact through APS journal splits...
2017: PloS One
Stephanie M Barbon, Jasmine V Buddingh, Ryan R Maar, Joe B Gilroy
The synthesis and characterization of a flexidentate pyridine-substituted formazanate ligand and its boron difluoride adducts, formed via two different coordination modes of the title ligand, are described. The first adduct adopted a structure that was typical of other boron difluoride adducts of triarylformazanate ligands and contained a free pyridine subsituent, while the second was formed via the chelation of nitrogen atoms from the formazanate backbone and the pyridine substituent. Stepwise protonation of the pydridine-functionalized adduct, which is essentially nonemissive, resulted in a significant increase in the fluorescence quantum yield up to a maximum of 18%, prompting the study of this adduct as a pH sensor...
September 18, 2017: Inorganic Chemistry
Bruno Marchal
After reviewing the basic of theology of Universal Numbers/Machines, as detailed in (Marchal, 2007), I illustrate how that body of thought might be used to shed some light upon the apparent dichotomy in Eastern/Western spirituality. This paper relies entirely on my previous inter-disciplinary work in mathematical logic, computer science and machine's theology, where "theology" is used here in the sense of Plato: it is the truth, or the "truth-theory" (in the sense of logicians) about a machine that the machine can either deduce from some of its primitive beliefs, or can be intuited in some sense that eventually is made clear through the modal logic of machine self-reference...
September 14, 2017: Progress in Biophysics and Molecular Biology
Henrik G Bohr, Irene Shim, Cy Stein, Henrik Ørum, Henrik F Hansen, Troels Koch
Important oligonucleotides in anti-sense research have been investigated in silico and experimentally. This involves quantum mechanical (QM) calculations and chromatography experiments on locked nucleic acid (LNA) phosphorothioate (PS) oligonucleotides. iso-potential electrostatic surfaces are essential in this study and have been calculated from the wave functions derived from the QM calculations that provide binding information and other properties of these molecules. The QM calculations give details of the electronic structures in terms of e...
September 15, 2017: Molecular Therapy. Nucleic Acids
Fabio Sterpone, Sébastien Doutreligne, Thanh Thuy Tran, Simone Melchionna, Marc Baaden, Phuong H Nguyen, Philippe Derreumaux
Biomolecules are complex machines that are optimized by evolution to properly fulfill or contribute to a variety of biochemical tasks in the cellular environment. Computer simulations based on quantum mechanics and atomistic force fields have been proven to be a powerful microscope for obtaining valuable insights into many biological, physical, and chemical processes. Many interesting phenomena involve, however, a time scale and a number of degrees of freedom, notably if crowding is considered, that cannot be explored at an atomistic resolution...
September 13, 2017: Biochemical and Biophysical Research Communications
L Dudy, J Aulbach, T Wagner, J Schäfer, R Claessen
Interacting electrons confined to only one spatial dimension display a wide range of unusual many-body quantum phenomena, ranging from Peierls instabilities to the breakdown of the canonical Fermi liquid paradigm to even unusual spin phenomena. The underlying physics is not only of tremendous fundamental interest, but may also have bearing on device functionality in future micro- and nanoelectronics with lateral extensions reaching the atomic limit. Metallic adatoms deposited on semiconductor surfaces may form self-assembled atomic nanowires, thus representing highly interesting and well-controlled solid-state realizations of such 1D quantum systems...
September 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Kimberly H Hartstein, Christian S Erickson, Emily Y Tsui, Arianna Marchioro, Daniel R Gamelin
We examine the effects of CdS shell growth on photochemical reduction of colloidal CdSe quantum dots (QDs) and describe the spectroscopic properties of the resulting n-type CdSe/CdS QDs. CdS shell growth greatly slows electron trapping. Because of this improvement, complete two-electron occupancy of the 1Se conduction-band orbital is achieved in CdSe/CdS QDs and found to be much more stable than in past experiments. Simultaneous photoluminescence at two different energies is now observed from QDs possessing two excess conduction-band electrons, reflecting competing recombination of discretized 1Se and 1Pe conduction-band electrons within photogenerated four-carrier negative tetrons (three electrons and one hole)...
September 20, 2017: ACS Nano
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"