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Quantum physics

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https://www.readbyqxmd.com/read/28079081/sideband-cooling-beyond-the-quantum-backaction-limit-with-squeezed-light
#1
Jeremy B Clark, Florent Lecocq, Raymond W Simmonds, José Aumentado, John D Teufel
Quantum fluctuations of the electromagnetic vacuum produce measurable physical effects such as Casimir forces and the Lamb shift. They also impose an observable limit-known as the quantum backaction limit-on the lowest temperatures that can be reached using conventional laser cooling techniques. As laser cooling experiments continue to bring massive mechanical systems to unprecedentedly low temperatures, this seemingly fundamental limit is increasingly important in the laboratory. Fortunately, vacuum fluctuations are not immutable and can be 'squeezed', reducing amplitude fluctuations at the expense of phase fluctuations...
January 11, 2017: Nature
https://www.readbyqxmd.com/read/28079064/lasing-action-from-photonic-bound-states-in-continuum
#2
Ashok Kodigala, Thomas Lepetit, Qing Gu, Babak Bahari, Yeshaiahu Fainman, Boubacar Kanté
In 1929, only three years after the advent of quantum mechanics, von Neumann and Wigner showed that Schrödinger's equation can have bound states above the continuum threshold. These peculiar states, called bound states in the continuum (BICs), manifest themselves as resonances that do not decay. For several decades afterwards the idea lay dormant, regarded primarily as a mathematical curiosity. In 1977, Herrick and Stillinger revived interest in BICs when they suggested that BICs could be observed in semiconductor superlattices...
January 11, 2017: Nature
https://www.readbyqxmd.com/read/28078631/investigation-of-solvent-effects-on-photophysical-properties-of-new-aminophthalimide-derivatives-based-on-methanesulfonate
#3
Ayse Tan, Ebru Bozkurt, Yunus Kara
Novel aminophthalimide derivatives were synthesized starting from (3aR,7aS)-2-(2-hydroxypropyl)-3a,4,7,7a-tetrahydro-1H-isoindole-1,3(2H)-dione (9) , and solvent effects on the photo-physical properties of these newly synthesized aminophthalimide derivatives (compounds 14 and 15) were investigated using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence measurements. Both absorption and fluorescence spectra exhibited bathochromic shift with the increased polarity of the solvents for both molecules...
January 11, 2017: Journal of Fluorescence
https://www.readbyqxmd.com/read/28071920/side-gate-tunable-josephson-junctions-at-the-laalo3-srtio3-interface
#4
Ana Mafalda R V L Monteiro, Dirk Jan Groenendijk, Nicola Manca, Emre Mulazimoglu, Srijit Goswami, Yaroslav Blanter, Lieven M K Vandersypen, Andrea D Caviglia
Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO3/SrTiO3 interface as a model system, we employ a single-step lithographic process to realize gate tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale...
January 10, 2017: Nano Letters
https://www.readbyqxmd.com/read/28059531/majorana-time-reversal-symmetries-a-fundamental-principle-for-sign-problem-free-quantum-monte%C3%A2-carlo-simulations
#5
Zi-Xiang Li, Yi-Fan Jiang, Hong Yao
A fundamental open issue in physics is whether and how the fermion sign problem in quantum Monte Carlo (QMC) simulations can be solved generically. Here, we show that Majorana-time-reversal (MTR) symmetries can provide a unifying principle to solve the fermion sign problem in interacting fermionic models. By systematically classifying Majorana-bilinear operators according to the anticommuting MTR symmetries they respect, we rigorously prove that there are two and only two fundamental symmetry classes which are sign-problem-free and which we call the "Majorana class" and "Kramers class," respectively...
December 23, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/28059528/estimating-the-coherence-of-noise-in-quantum-control-of-a-solid-state-qubit
#6
Guanru Feng, Joel J Wallman, Brandon Buonacorsi, Franklin H Cho, Daniel K Park, Tao Xin, Dawei Lu, Jonathan Baugh, Raymond Laflamme
To exploit a given physical system for quantum information processing, it is critical to understand the different types of noise affecting quantum control. Distinguishing coherent and incoherent errors is extremely useful as they can be reduced in different ways. Coherent errors are generally easier to reduce at the hardware level, e.g., by improving calibration, whereas some sources of incoherent errors, e.g., T_{2}^{*} processes, can be reduced by engineering robust pulses. In this work, we illustrate how purity benchmarking and randomized benchmarking can be used together to distinguish between coherent and incoherent errors and to quantify the reduction in both of them due to using optimal control pulses and accounting for the transfer function in an electron spin resonance system...
December 23, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/28059385/investigation-of-hollow-cylindrical-metal-terahertz-waveguides-suitable-for-cryogenic-environments
#7
R Wallis, R Degl Innocenti, D S Jessop, O Mitrofanov, C M Bledt, J E Melzer, J A Harrington, H E Beere, D A Ritchie
The field of terahertz (THz) waveguides continues to grow rapidly, with many being tailored to suit the specific demands of a particular final application. Here, we explore waveguides capable of enabling efficient and accurate power delivery within cryogenic environments (< 4 K). The performance of extruded hollow cylindrical metal waveguides made of un-annealed and annealed copper, as well as stainless steel, have been investigated for bore diameters between 1.75 - 4.6 mm, and at frequencies of 2.0, 2.85 and 3...
December 26, 2016: Optics Express
https://www.readbyqxmd.com/read/28054936/silicon-and-germanium-nanowire-electronics-physics-of-conventional-and-unconventional-transistors
#8
Walter M Weber, Thomas Mikolajick
Research in the field of electronics of one-dimensional group-IV semiconductor structures has attracted increasing attention over the past 15 years. The exceptional combination of the unique one-dimensional electronic transport properties with the mature material know-how of highly integrated silicon and germanium technology holds the promise of enhancing state-of-the-art electronics. In addition of providing conduction channels that can bring conventional field effect transistors to the uttermost scaling limits, the physics of 1-D group IV nanowires endows new device principles...
January 5, 2017: Reports on Progress in Physics
https://www.readbyqxmd.com/read/28053232/directional-emission-from-dye-functionalized-plasmonic-dna-superlattice-microcavities
#9
Daniel J Park, Jessie C Ku, Lin Sun, Clotilde M Lethiec, Nathaniel P Stern, George C Schatz, Chad A Mirkin
Three-dimensional plasmonic superlattice microcavities, made from programmable atom equivalents comprising gold nanoparticles functionalized with DNA, are used as a testbed to study directional light emission. DNA-guided nanoparticle colloidal crystallization allows for the formation of micrometer-scale single-crystal body-centered cubic gold nanoparticle superlattices, with dye molecules coupled to the DNA strands that link the particles together, in the form of a rhombic dodecahedron. Encapsulation in silica allows one to create robust architectures with the plasmonically active particles and dye molecules fixed in space...
January 4, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28051866/photochromic-mechanism-of-a-bridged-diarylethene-combined-electronic-structure-calculations-and-nonadiabatic-dynamics-simulations
#10
Yating Wang, Yuan-Jun Gao, Qian Wang, Ganglong Cui
Intramolecularly bridged diarylethenes exhibit improved photocyclization quantum yields because the anti-syn isomerization that originally suppresses photocyclization in classical diarylethenes is blocked. Experimentally, three possible channels have been proposed to interpret experimental observation, but many details of photochromic mechanism remain ambiguous. In this work we have employed a series of electronic structure methods (OM2/MRCI, DFT, TDDFT, RI-CC2, DFT/MRCI, and CASPT2) to comprehensively research excited state properties, photocyclization, and photoreversion dynamics of 1,2-dicyano[2,2]metacyclophan-1-ene...
January 4, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28051145/enhancement-effect-of-mass-imbalance-on-fulde-ferrell-larkin-ovchinnikov-type-of-pairing-in-fermi-fermi-mixtures-of-ultracold-quantum-gases
#11
Jibiao Wang, Yanming Che, Leifeng Zhang, Qijin Chen
Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a (6)Li-(40)K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level...
January 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28051060/experimental-observation-of-anomalous-topological-edge-modes-in-a-slowly-driven-photonic-lattice
#12
Sebabrata Mukherjee, Alexander Spracklen, Manuel Valiente, Erika Andersson, Patrik Öhberg, Nathan Goldman, Robert R Thomson
Topological quantum matter can be realized by subjecting engineered systems to time-periodic modulations. In analogy with static systems, periodically driven quantum matter can be topologically classified by topological invariants, whose non-zero value guarantees the presence of robust edge modes. In the high-frequency limit of the drive, topology is described by standard topological invariants, such as Chern numbers. Away from this limit, these topological numbers become irrelevant, and novel topological invariants must be introduced to capture topological edge transport...
January 4, 2017: Nature Communications
https://www.readbyqxmd.com/read/28048923/su-f-i-69-absorbed-dose-estimation-for-a-commercially-available-microct-scanner-with-various-filtration-techniques
#13
A Lau, H Liu, L Ren, S Ahmad, Y Chen
PURPOSE: To quantify the simulated mean absorbed dose per technique (cGy/mAs) from a commercially available microCT scanner using various filtration techniques. METHODS: Monte Carlo simulations using the Geant4 toolkit (version 10) was used utilizing the standard electromagnetic physics model. The Quantum FX microCT scanner (PerkinElmer, Waltham, MA) was modeled incorporating measured energy spectra and spatial dimensions of nominal source-to-object (SOD) distances...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047794/su-g-iep3-09-investigating-the-interplay-of-antiscatter-grids-with-modern-detectors-and-image-processing-in-digital-radiography
#14
A Sanchez, K Little, M Baad, I Reiser, Z F Lu, K Feinstein
PURPOSE: To use phantom and simulation experiments to relate technique factors, patient size and antiscatter grid use to image quality in portable digital radiography (DR), in light of advancements in detector design and image processing. METHODS: Image contrast-to-noise ratio (CNR) on a portable DR system (MobileDaRt Evolution, Shimadzu) was measured by imaging four aluminum inserts of varying thickness, superimposed on a Lucite slab phantom using a pediatric abdominal protocol...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047608/su-d-brb-05-quantum-learning-for-knowledge-based-response-adaptive-radiotherapy
#15
I El Naqa, R Ten
PURPOSE: There is tremendous excitement in radiotherapy about applying data-driven methods to develop personalized clinical decisions for real-time response-based adaptation. However, classical statistical learning methods lack in terms of efficiency and ability to predict outcomes under conditions of uncertainty and incomplete information. Therefore, we are investigating physics-inspired machine learning approaches by utilizing quantum principles for developing a robust framework to dynamically adapt treatments to individual patient's characteristics and optimize outcomes...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28045146/synthesis-driven-structure-dependent-optical-behavior-in-phase-tunable-nayf4-yb-er-based-motifs-and-associated-heterostructures
#16
Haiqing Liu, Jinkyu Han, Coray McBean, Crystal S Lewis, Prahlad Kumar Routh, Mircea Cotlet, Stanislaus S Wong
Understanding the key parameters necessary for generating uniform Er,Yb co-activated NaYF4 possessing various selected phases (i.e. cubic or hexagonal) represents an important chemical strategy towards tailoring optical behavior in these systems. Herein, we report on a straightforward hydrothermal synthesis in which the separate effects of reaction temperature, reaction time, and precursor stoichiometry in the absence of any surfactant were independently investigated. Interestingly, the presence and the concentration of NH4OH appear to be the most critical determinants of the phase and morphology...
January 3, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28045059/how-a-single-particle-simultaneously-modifies-the-physical-reality-of-two-distant-others-a-quantum-nonlocality-and-weak-value-study
#17
Bertúlio de Lima Bernardo, Askery Canabarro, Sérgio Azevedo
The concept of wave-particle duality, which is a key element of quantum theory, has been remarkably found to manifest itself in several experimental realizations as in the famous double-slit experiment. In this specific case, a single particle seems to travel through two separated slits simultaneously. Nevertheless, it is never possible to measure it in both slits, which naturally appears as a manifestation of the collapse postulate. In this respect, one could as well ask if it is possible to "perceive" the presence of the particle at the two slits simultaneously, once its collapse could be avoided...
January 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28044312/optimization-of-contrast-enhanced-breast-imaging-analysis-using-a-cascaded-linear-system-model
#18
Yue-Houng Hu, David A Scaduto, Wei Zhao
PURPOSE: Contrast-enhanced (CE) breast imaging involves the injection contrast agents (i.e., iodine) to increase conspicuity of malignant lesions. CE imaging may be used in conjunction with digital mammography (DM) or digital breast tomosynthesis (DBT) and has shown promise in improving diagnostic specificity. Both CE-DM and CE-DBT techniques require optimization as clinical diagnostic tools. Physical factors including x-ray spectra, subtraction technique, and the signal from iodine contrast, must be considered to provide the greatest object detectability and image quality...
November 21, 2016: Medical Physics
https://www.readbyqxmd.com/read/28041845/inverse-bayesian-inference-as-a-key-of-consciousness-featuring-a-macroscopic-quantum-logical-structure
#19
Yukio-Pegio Gunji, Shuji Shinohara, Taichi Haruna, Vasileios Basios
To overcome the dualism between mind and matter and to implement consciousness in science, a physical entity has to be embedded with a measurement process. Although quantum mechanics has been regarded as a candidate for implementing consciousness, nature at its macroscopic level is inconsistent with quantum mechanics. We propose a measurement-oriented inference system comprising Bayesian and inverse Bayesian inferences. While Bayesian inference contracts probability space, the newly defined inverse one relaxes the space...
December 29, 2016: Bio Systems
https://www.readbyqxmd.com/read/28040579/cathodoluminescence-in-the-scanning-transmission-electron-microscope
#20
M Kociak, L F Zagonel
Cathodoluminescence (CL) is a powerful tool for the investigation of optical properties of materials. In recent years, its combination with scanning transmission electron microscopy (STEM) has demonstrated great success in unveiling new physics in the field of plasmonics and quantum emitters. Most of these results were not imaginable even twenty years ago, due to conceptual and technical limitations. The purpose of this review is to present the recent advances that broke these limitations, and the new possibilities offered by the modern STEM-CL technique...
December 19, 2016: Ultramicroscopy
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