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Quantum coherence

Weiwei Xie, Wolfgang Domcke
Trajectory surface hopping (TSH) methods have been widely used for the study of nonadiabatic molecular dynamics. In the present work, the accuracy of two TSH algorithms, Tully's fewest switching algorithm and an algorithm based on the Landau-Zener formula, has been critically evaluated in comparison with exact nonadiabatic quantum dynamics calculations for a model of the photoinduced hydrogen-atom dissociation reaction in phenol. The model consists of three electronic states (S0, (1)ππ(*), (1)πσ(*)) and two nuclear degrees of freedom (the OH stretching coordinate and CCOH dihedral angle) and displays two successive conical intersections ((1)ππ(*)/(1)πσ(*) and (1)πσ(*)/S0)...
November 14, 2017: Journal of Chemical Physics
Fei Yao, Dechao Li, Haodi Liu, Libin Fu, Xiaoguang Wang
Majorana stars are visual representation for a quantum pure state. For some states, the corresponding majorana stars are located on one curve on the Block sphere. However, it is lack of exact curve equations for them. To find the exact equations, we consider a superposition of two bosonic coherent states with an arbitrary relative phase. We analytically give the curve equation and find that the curve always goes through the North pole on the Block sphere. Furthermore, for the superpositions of SU(1,1) coherent states, we find the same curve equation...
November 14, 2017: Scientific Reports
X N Feng, L F Wei
Quantum coherence is one of the old but always important concepts in quantum mechanics, and now it has been regarded as a necessary resource for quantum information processing and quantum metrology. However, the question of how to quantify the quantum coherence has just been paid the attention recently (see, e.g., Baumgratz et al. PRL, 113. 140401 (2014)). In this paper we verify that the well-known quantum Fisher information (QFI) can be utilized to quantify the quantum coherence, as it satisfies the monotonicity under the typical incoherent operations and the convexity under the mixing of the quantum states...
November 14, 2017: Scientific Reports
Taek Jeong, Jumi Park, Han Seb Moon
In quantum memory based on an atomic medium, we may have a question about whether all information on the stored light is preserved. In particular, the phase coherence between the stored and retrieval light pulses is very interesting, because it can indicate the relationship between the coherence time and storage time of the light. In this paper, we investigate the phase coherence time of light stored in a warm atomic vapor, by examining the beat-note interference between the retrieval light pulse and a reference light beam optically delayed using an optical fiber...
November 14, 2017: Scientific Reports
Li-Chi Kao, Bo-Jia Huang, Yu-En Jeng, Kai-Teng Tu, Shang-Jui Chiu, Ching-Shun Ku, Kuang-Yao Lo
Zn dots are potential solutions for metal contacts in future nanodevices. The metastable states that exist at the interface between Zn quantum dots and oxide-free Si(111) surfaces can suppress the development of the complete relaxation and increase the size of Zn dots. In this work, the actual heat consumption of the structural evolution of Zn dots resulting from extrinsic thermal effect was analyzed. Zn dots were coherently grown on oxide-free Si(111) through magnetron RF sputtering. A compensative optical method combined with reflective second harmonic generation (RSHG) and synchrotron X-ray diffraction (XRD) was developed to statistically analyze the thermal effect on the Zn dot system...
November 14, 2017: Nanotechnology
Nathan Andrew Neff-Mallon, John C Wright
Triply Resonant Sum Frequency (TRSF) and Doubly Vibrationally Enhanced (DOVE) spectroscopies are examples of a recently developed family of Coherent Multidimensional Spectroscopies (CMDS) that are analogous to current analytical spectroscopies. They are based on creating quantum mechanical superposition states that are fully coherent and lack intermediate quantum state populations that cause quenching or other relaxation effects. They provide multidimensional spectral fingerprints consisting of mixtures of vibrational and electronic states...
November 14, 2017: Analytical Chemistry
M Farhat, S Kais, F H Alharbi
In this work, we report modeling of non-Markovian open quantum systems, consisting of an excitonic dimer that displays memory effect due to time delayed interaction with its environment. We, indeed investigate the effect of these time delays on quantum coherence and excitation dynamical behavior in the time domain generally considered for photosynthetic experiments (few hundred femtoseconds). In particular, we show that the coherence is maintained for periods proportional to time delays. Additionally, if delay is taken into account, coupling to the environment can be tuned to lower values, unlike in previous studies...
November 13, 2017: Scientific Reports
Harold W Mackenzie, D Flemming Hansen
Arginine side-chains are often key for enzyme catalysis, protein-ligand and protein-protein interactions. The importance of arginine stems from the ability of the terminal guanidinium group to form many key interactions, such as hydrogen bonds and salt bridges, as well as its perpetual positive charge. We present here an arginine (13)C(ζ)-detected NMR experiment in which a double-quantum coherence involving the two (15)N(η) nuclei is evolved during the indirect chemical shift evolution period. As the precession frequency of the double-quantum coherence is insensitive to exchange of the two (15)N(η); this new approach is shown to eliminate the previously deleterious line broadenings of (15)N(η) resonances caused by the partially restricted rotation about the C(ζ)-N(ε) bond...
November 10, 2017: Journal of Biomolecular NMR
He-Liang Huang, Han-Sen Zhong, Tan Li, Feng-Guang Li, Xiang-Qun Fu, Shuo Zhang, Xiang Wang, Wan-Su Bao
Boson sampling is strongly believed to be intractable for classical computers but solvable with photons in linear optics, which raises widespread concern as a rapid way to demonstrate the quantum supremacy. However, due to its solution is mathematically unverifiable, how to certify the experimental results becomes a major difficulty in the boson sampling experiment. Here, we develop a statistical analysis scheme to experimentally certify the collision-free boson sampling. Numerical simulations are performed to show the feasibility and practicability of our scheme, and the effects of realistic experimental conditions are also considered, demonstrating that our proposed scheme is experimentally friendly...
November 10, 2017: Scientific Reports
Gufei Zhang, Tomas Samuely, Hongchu Du, Zheng Xu, Liwang Liu, Oleksandr Onufriienko, Paul W May, Johan Vanacken, Pavol Szabó, Jozef Kačmarčík, Haifeng Yuan, Peter Samuely, Rafal E Dunin-Borkowski, Johan Hofkens, Victor V Moshchalkov
In the presence of disorder, superconductivity exhibits short-range characteristics linked to localized Cooper pairs which are responsible for anomalous phase transitions and the emergence of quantum states such as the bosonic insulating state. Complementary to well-studied homogeneously disordered superconductors, superconductor-normal hybrid arrays provide tunable realizations of the degree of granular disorder for studying anomalous quantum phase transitions. Here, we investigate the superconductor-bosonic dirty metal transition in disordered nanodiamond arrays as a function of the dispersion of intergrain spacing, which ranges from angstroms to micrometers...
November 13, 2017: ACS Nano
Darin James Ulness, Daniel B Turner
Two-quantum two-dimensional electronic spectroscopy (2Q 2D ES) may provide a measure of electron-correlation energies in molecules. Attempts to obtain this profound but elusive signal have relied on experimental implementations using femtosecond laser pulses, which induce an overwhelming background signal of nonresonant response. Here we explore theoretically the signatures of electron correlation in coherent 2Q 2D ES measurements that use spectrally incoherent light, I((4)) 2Q 2D ES. One can use such fields to suppress nonresonant response, and therefore this method may better isolate the desired signature of electron correlation...
November 9, 2017: Journal of Physical Chemistry. A
Colin J Lambert, Shi-Xia Liu
This overview will give a glimpse into chemical design principles for gating quantum interference (QI) effects in molecular-scale devices. Direct observation of room temperature QI in single-molecule junctions has stimulated growing interest in fabrication of tailor-made molecular electronic devices. Herein, we outline a new conceptual advance in the scientific understanding and technological know-how necessary to control QI effects in single molecules by chemical modification. We start by discussing QI from a chemical viewpoint and then describe a new magic ratio rule (MRR), which captures a minimal description of connectivity-driven charge transport and provides a useful starting point for chemists to design appropriate molecules for molecular electronics with desired functions...
November 9, 2017: Chemistry: a European Journal
Zhaosheng Zhang, Run Long, Marina V Tokina, Oleg V Prezhdo
Delayed high-energy fluorescence observed experimentally in methylammonium lead bromine CH3NH3PbBr3 (MAPbBr3) demonstrates long-lived energetic charge carriers with extremely high mobilities that can be used to enhance photon-to-electron conversion efficiency of perovskite solar cells. It has been suggested that hot fluorescence is associated with reorientational motions of the MA molecules. We support this hypothesis by time-domain ab initio quantum dynamics calculations showing that reorientation of the MA molecules can affect strongly the perovskite emission energy and lifetime...
November 8, 2017: Journal of the American Chemical Society
Dengke Zhang, Xiao-Qing Luo, Yi-Pu Wang, Tie-Fu Li, J Q You
Magnon-polaritons are hybrid light-matter quasiparticles originating from the strong coupling between magnons and photons. They have emerged as a potential candidate for implementing quantum transducers and memories. Owing to the dampings of both photons and magnons, the polaritons have limited lifetimes. However, stationary magnon-polariton states can be reached by a dynamical balance between pumping and losses, so the intrinsically nonequilibrium system may be described by a non-Hermitian Hamiltonian. Here we design a tunable cavity quantum electrodynamics system with a small ferromagnetic sphere in a microwave cavity and engineer the dissipations of photons and magnons to create cavity magnon-polaritons which have non-Hermitian spectral degeneracies...
November 8, 2017: Nature Communications
A Yu Dmitriev, R Shaikhaidarov, V N Antonov, T Hönigl-Decrinis, O V Astafiev
Superconducting quantum systems (artificial atoms) have been recently successfully used to demonstrate on-chip effects of quantum optics with single atoms in the microwave range. In particular, a well-known effect of four wave mixing could reveal a series of features beyond classical physics, when a non-linear medium is scaled down to a single quantum scatterer. Here we demonstrate the phenomenon of quantum wave mixing (QWM) on a single superconducting artificial atom. In the QWM, the spectrum of elastically scattered radiation is a direct map of the interacting superposed and coherent photonic states...
November 7, 2017: Nature Communications
Siwen Zhao, Yiming Wu, Kaixuan Zhang, Huaiyi Ding, Dongxue Du, Jiyin Zhao, Nan Pan, Xiaoping Wang
We carefully prepared interfacial Al-doped (IAD) and interfacial natively-doped (IND) ZnO nanowires (NWs) by introducing atomic-layer interfacial Δ-doping between the two steps of CVD growth. Variable-temperature electron transport as well as magnetotransport behaviours of these NWs were systematically investigated. By virtue of the unique architecture and the quality-guaranteed growth technique, a series of quantum interference effects were clearly observed in the IAD ZnO NWs, including weak localization, universal conductance fluctuation and Altshuler-Aronov-Spivak oscillations...
November 16, 2017: Nanoscale
Victor Nadtochenko, Nikolay Denisov, Arseniy Aybush, Fedor Gostev, Ivan Shelaev, Andrey Titov, Stanislav Umanskiy, And Dmitry Cherepanov
The main goal of the present work is to study the coherent phonon in strongly confined CdSe quantum dots (QDs) under varied pump fluences. The main characteristics of coherent phonons (amplitude, frequency, phase, spectrogram) of CdSe QDs under the red-edge pump of the excitonic band [1S(e)-1S3/2(h)] are reported. We demonstrate for the first time that the amplitude of the coherent optical longitudinal-optical (LO) phonon at 6.16 THz excited in CdSe nanoparticles by a femtosecond unchirped pulse shows a non-monotone dependence on the pump fluence...
November 4, 2017: Nanomaterials
Ramya Billur, David Ban, T Michael Sabo, Muriel Christine Maurer
Thrombin participates in procoagulation, anticoagulation, and platelet activation. This enzyme contains anion binding exosites, ABE I and ABE II, which attract regulatory biomolecules. As prothrombin is activated to thrombin, pro-ABE I is converted into mature ABE I. Unexpectedly, certain ligands can bind to pro-ABE I specifically. Moreover, knowledge is lacking on changes in conformation and affinity that occur at the individual residue level as pro-ABE I is converted to ABE I. Such changes are transient and failed to be captured by crystallography...
November 7, 2017: Biochemistry
Stéphanie Valleau, Romain A Studer, Florian Häse, Christoph Kreisbeck, Rafael G Saer, Robert E Blankenship, Eugene I Shakhnovich, Alán Aspuru-Guzik
We present a study on the evolution of the Fenna-Matthews-Olson bacterial photosynthetic pigment-protein complex. This protein complex functions as an antenna. It transports absorbed photons-excitons-to a reaction center where photosynthetic reactions initiate. The efficiency of exciton transport is therefore fundamental for the photosynthetic bacterium's survival. We have reconstructed an ancestor of the complex to establish whether coherence in the exciton transport was selected for or optimized over time...
October 25, 2017: ACS Central Science
Joaquín Barroso-Flores
No abstract text is available yet for this article.
October 25, 2017: ACS Central Science
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