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Quantum physics

F D Parmentier, T Cazimajou, Y Sekine, H Hibino, H Irie, D C Glattli, N Kumada, P Roulleau
We have observed the well-kown quantum Hall effect (QHE) in epitaxial graphene grown on silicon carbide (SiC) by using, for the first time, only commercial NdFeB permanent magnets at low temperature. The relatively large and homogeneous magnetic field generated by the magnets, together with the high quality of the epitaxial graphene films, enables the formation of well-developed quantum Hall states at Landau level filling factors v = ±2, commonly observed with superconducting electro-magnets. Furthermore, the chirality of the QHE edge channels can be changed by a top gate...
December 6, 2016: Scientific Reports
Xiao Hu, Chenbo Dong, Rigu Su, Quan Xu, Cerasela Zoica Dinu
The next generation of nanowires that could advance the integration of functional nanosystems into synthetic applications from photocatalysis to optical devices need to demonstrate increased ability to promote electron transfer at their interfaces while ensuring optimum quantum confinement. Herein we used the biological recognition and the self-assembly properties of tubulin, a protein involved in building the filaments of cellular microtubules, to create stable, free standing and conductive sulfur-doped carbon nanodots-based conductive bio-hybrids...
December 6, 2016: Scientific Reports
B Silva, C Sánchez Muñoz, D Ballarini, A González-Tudela, M de Giorgi, G Gigli, K West, L Pfeiffer, E Del Valle, D Sanvitto, F P Laussy
The Hanbury Brown-Twiss effect is one of the celebrated phenomenologies of modern physics that accommodates equally well classical (interferences of waves) and quantum (correlations between indistinguishable particles) interpretations. The effect was discovered in the late thirties with a basic observation of Hanbury Brown that radio-pulses from two distinct antennas generate signals on the oscilloscope that wiggle similarly to the naked eye. When Hanbury Brown and his mathematician colleague Twiss took the obvious step to propose bringing the effect in the optical range, they met with considerable opposition as single-photon interferences were deemed impossible...
December 6, 2016: Scientific Reports
Stepan Stehlik, Marian Varga, Martin Ledinsky, Daria Miliaieva, Halyna Kozak, Viera Skakalova, Clemens Mangler, Timothy J Pennycook, Jannik C Meyer, Alexander Kromka, Bohuslav Rezek
Detonation nanodiamonds (DNDs) with a typical size of 5 nm have attracted broad interest in science and technology. Further size reduction of DNDs would bring these nanoparticles to the molecular-size level and open new prospects for research and applications in various fields, ranging from quantum physics to biomedicine. Here we show a controllable size reduction of the DND mean size down to 1.4 nm without significant particle loss and with additional disintegration of DND core agglutinates by air annealing, leading to a significantly narrowed size distribution (±0...
December 2, 2016: Scientific Reports
Jin-Jin Ding, Hou-Dao Zhang, Yao Wang, Rui-Xue Xu, Xiao Zheng, YiJing Yan
A unified theory for minimum exponential-term ansatzes on bath correlation functions is proposed for numerically efficient and physically insightful treatments of non-Markovian environment influence on quantum systems. For a general Brownian oscillator bath of frequency Ω and friction ζ, the minimum ansatz results in the correlation function a bi-exponential form, with the effective Ω¯ and friction ζ¯ being temperature dependent and satisfying Ω¯/Ω=(ζ¯/ζ)(1/2)=r¯BO/rBO≤ 1, where r¯BO=ζ¯/(2Ω¯) and rBO=ζ/(2Ω)...
November 28, 2016: Journal of Chemical Physics
Weijie Mai, Xiaokang Song, Ping Jiang, Wenzhong Wang, Li Yu, Jiasen Zhang
Plasmon-based fluorescence modulation has led to important advances in various fields and has paved the way toward promising scientific research aimed at enabling new applications. However, the modulation of fluorescence properties based on both localized surface plasmon (LSP) and cavity modes of propagating surface plasmon polaritons (SPPs) are rarely reported. Here, we raster scanned a hybrid nanowire (HNW) with quantum dots (QDs) adsorbed onto a Ag nanowire (NW) and obtained two-photon fluorescence (TPF) maps of the intensity and decay rate...
November 28, 2016: Optics Express
Wen-Jing Chu, Ming Yang, Guo-Zhu Pan, Qing Yang, Zhuo-Liang Cao
An optical scheme for simulating nonlocality distillation is proposed in post-quantum regime. The nonlocal boxes are simulated by measurements on appropriately pre- and post-selected polarization entangled photon pairs, i.e. post-quantum nonlocality is simulated by exploiting fair-sampling loophole in a Bell test. Mod 2 addition on the outputs of two nonlocal boxes combined with pre- and post-selection operations constitutes the key operation of simulating nonlocality distillation. This scheme provides a possible tool for the experimental study on the nonlocality in post-quantum regime and the exact physical principle precisely distinguishing physically realizable correlations from nonphysical ones...
November 28, 2016: Optics Express
Yong Siah Teo, Dmitri Mogilevtsev, Alexander Mikhalychev, Jaroslav Řeháček, Zdeněk Hradil
In continuous-variable tomography, with finite data and limited computation resources, reconstruction of a quantum state of light is performed on a finite-dimensional subspace. In principle, the data themselves encode all information about the relevant subspace that physically contains the state. We provide a straightforward and numerically feasible procedure to uniquely determine the appropriate reconstruction subspace by extracting this information directly from the data for any given unknown quantum state of light and measurement scheme...
December 1, 2016: Scientific Reports
(no author information available yet)
No abstract text is available yet for this article.
November 30, 2016: Nature
Jun Jing, Lian-Ao Wu, Adolfo Del Campo
Quantum physics dictates fundamental speed limits during time evolution. We present a quantum speed limit governing the generation of nonclassicality and the mutual incompatibility of two states connected by time evolution. This result is used to characterize the timescale required to generate a given amount of quantumness under an arbitrary physical process. The bound is found to be tight under pure dephasing dynamics. More generally, our analysis reveals the dependence on the initial and final states and non-Markovian effects...
November 30, 2016: Scientific Reports
Clemens Schäfermeier, Hugo Kerdoncuff, Ulrich B Hoff, Hao Fu, Alexander Huck, Jan Bilek, Glen I Harris, Warwick P Bowen, Tobias Gehring, Ulrik L Andersen
Laser cooling is a fundamental technique used in primary atomic frequency standards, quantum computers, quantum condensed matter physics and tests of fundamental physics, among other areas. It has been known since the early 1990s that laser cooling can, in principle, be improved by using squeezed light as an electromagnetic reservoir; while quantum feedback control using a squeezed light probe is also predicted to allow improved cooling. Here we show the implementation of quantum feedback control of a micro-mechanical oscillator using squeezed probe light...
November 29, 2016: Nature Communications
Li-Xian Wang, Shuo Wang, Jin-Guang Li, Cai-Zhen Li, Jun Xu, Dapeng Yu, Zhi-Min Liao
Three-dimensional (3D) Dirac semimetals are featured by 3D linear energy-momentum dispersion relation, which have been proposed to be a desirable system to study Dirac fermions in 3D space and Weyl fermions in solid-state materials. Significantly, to reveal exotic transport properties of Dirac semimetals, the Fermi level should be close to the Dirac point, around which the linear dispersion is retained. Here we report the magnetotransport properties near the Dirac point in Cd3As2 nanowires, manifesting the evolution of band structure under magnetic field...
November 29, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Leonid I Perlovsky
Is it possible to turn psychology into "hard science"? Physics of the mind follows the fundamental methodology of physics in all areas where physics have been developed. What is common among Newtonian mechanics, statistical physics, quantum physics, thermodynamics, theory of relativity, astrophysics… and a theory of superstrings? The common among all areas of physics is a methodology of physics discussed in the first few lines of the paper. Is physics of the mind possible? Is it possible to describe the mind based on the few first principles as physics does? The mind with its variabilities and uncertainties, the mind from perception and elementary cognition to emotions and abstract ideas, to high cognition...
2016: Frontiers in Systems Neuroscience
R W Bouwman, R E van Engen, M J M Broeders, G J den Heeten, D R Dance, K C Young, W J H Veldkamp
PURPOSE: In mammography, images are processed prior to display. Current methodologies based on physical image quality measurements are however not designed for the evaluation of processed images. Model observers (MO) might be suitable for this evaluation. The aim of this study was to investigate whether the non-pre-whitening (NPW) MO can be used to predict human observer performance in mammography-like images by including different aspects of the human visual system (HVS). METHODS: The correlation between human and NPW MO performance has been investigated for the detection of disk shaped objects in simulated white noise (WN) and clustered lumpy backgrounds (CLB), representing quantum noise limited and mammography-like images respectively...
November 23, 2016: Physica Medica: PM
Jose Luis Rosales, Vicente Martin
Feynman's prescription for a quantum simulator was to find a Hamitonian for a system that could serve as a computer. The Pólya-Hilbert conjecture proposed the demonstration of Riemann's hypothesis through the spectral decomposition of Hermitian operators. Here we study the problem of decomposing a number into its prime factors, N=xy, using such a simulator. First, we derive the Hamiltonian of the physical system that simulates a new arithmetic function formulated for the factorization problem that represents the energy of the computer...
November 11, 2016: Physical Review Letters
Yue Chang, Alejandro González-Tudela, Carlos Sánchez Muñoz, Carlos Navarrete-Benlloch, Tao Shi
The development, characterization, and control of N-photon sources are instrumental for quantum technological applications. This work constitutes a step forward in this direction, where we propose a cavity quantum electrodynamics setup designed for the generation of photon pairs. We identify both the regime where our system works as a deterministic down-converter of a single input photon and as an optimal two-photon source under weak continuous driving. We use both the scattering and master equation formalisms to characterize the system, and from their connection naturally arises a physical criterion characterizing when weakly driven systems behave as continuous antibunched two-photon sources...
November 11, 2016: Physical Review Letters
Lei Wang, Jian Yang
At the beginning of the twentieth century, Japan and China, each for its own reasons, invited the famous physicist Niels Bohr to visit and give lectures. Bohr accepted their invitations and made the trip in 1937; however, the topics of his lectures in the two countries differed. In Japan, he mainly discussed quantum mechanics and philosophy, whereas in China, he focused more on atomic physics. This paper begins with a detailed review of Bohr's trip to Japan and China in 1937, followed by a discussion of the impact of each trip from the perspective of the social context...
November 21, 2016: Endeavour
Sandeep K Reddy, Shelby C Straight, Pushp Bajaj, C Huy Pham, Marc Riera, Daniel R Moberg, Miguel A Morales, Chris Knight, Andreas W Götz, Francesco Paesani
The MB-pol many-body potential has recently emerged as an accurate molecular model for water simulations from the gas to the condensed phase. In this study, the accuracy of MB-pol is systematically assessed across the three phases of water through extensive comparisons with experimental data and high-level ab initio calculations. Individual many-body contributions to the interaction energies as well as vibrational spectra of water clusters calculated with MB-pol are in excellent agreement with reference data obtained at the coupled cluster level...
November 21, 2016: Journal of Chemical Physics
Hong Hee Kim, Joon-Suh Park, Il Ki Han, Sung Ok Won, Cheolmin Park, Do Kyung Hwang, Won Kook Choi
Colloidal quantum dots (QDs) have been extensively studied for optoelectronic and biological applications due to their unique physical and optical properties. In particular, among the optoelectronics applications, the white light emitting diode (WLED) has great potential in flat panel displays and solid-state lighting. Herein, we demonstrate a novel, facile, and efficient technique for the synthesis of CdTe/ZnO/GO quasi-core-shell-shell hybrid quantum dots containing the CdTe core with multi shells of ZnO and graphene oxide (GO) and fabrication of WQDLEDs...
December 1, 2016: Nanoscale
Mattias T Johnsson, Gavin K Brennen, Jason Twamley
Precision measurements of gravity can provide tests of fundamental physics and are of broad practical interest for metrology. We propose a scheme for absolute gravimetry using a quantum magnetomechanical system consisting of a magnetically trapped superconducting resonator whose motion is controlled and measured by a nearby RF-SQUID or flux qubit. By driving the mechanical massive resonator to be in a macroscopic superposition of two different heights our we predict that our interferometry protocol could, subject to systematic errors, achieve a gravimetric sensitivity of Δg/g ~ 2...
November 21, 2016: Scientific Reports
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