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Quantum coherence

Yonghui Chen, Chen Xu, Yibo Zhou, Khan Maaz, Huijun Yao, Dan Mo, Shuangbao Lyu, Jinglai Duan, Jie Liu
Parallel arrays of Ni nanotubes with an external diameter of 150 nm, a wall thickness of 15 nm, and a length of 1.2 ± 0.3 µm were successfully fabricated in ion-track etched polycarbonate (PC) templates by electrochemical deposition. The morphology and crystal structure of the nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Structural analyses indicate that Ni nanotubes have a polycrystalline structure with no preferred orientation...
December 1, 2016: Nanomaterials
Johannes Gooth, Mattias Borg, Heinz Schmid, Vanessa Schaller, Stephan Wirths, Kirsten E Moselund, Mathieu Luisier, Siegfried Karg, Heike Riel
Coherent interconnection of quantum bits remains an ongoing challenge in quantum information technology. Envisioned hardware to achieve this goal is based on semiconductor nanowire (NW) circuits, comprising individual NW devices that are linked through ballistic interconnects. However, maintaining the sensitive ballistic conduction and confinement conditions across NW intersections is a non-trivial problem. Here, we go beyond the characterization of a single NW device and demonstrate ballistic 1D quantum transport in InAs NW cross-junctions, monolithically integrated on Si...
March 23, 2017: Nano Letters
Carlos A Melo-Luna, Cristian E Susa, Andrés F Ducuara, Astrid Barreiro, John H Reina
Game theory is a well established branch of mathematics whose formalism has a vast range of applications from the social sciences, biology, to economics. Motivated by quantum information science, there has been a leap in the formulation of novel game strategies that lead to new (quantum Nash) equilibrium points whereby players in some classical games are always outperformed if sharing and processing joint information ruled by the laws of quantum physics is allowed. We show that, for a bipartite non zero-sum game, input local quantum correlations, and separable states in particular, suffice to achieve an advantage over any strategy that uses classical resources, thus dispensing with quantum nonlocality, entanglement, or even discord between the players' input states...
March 22, 2017: Scientific Reports
Shaoyin Fang, Ruidan Zhu, Tianshu Lai
Spin relaxation dynamics of holes in intrinsic GaAs quantum wells is studied using time-resolved circular dichromatic absorption spectroscopy at room temperature. It is found that ultrafast dynamics is dominated by the cooperative contributions of band filling and many-body effects. The relative contribution of the two effects is opposite in strength for electrons and holes. As a result, transient circular dichromatic differential transmission (TCD-DT) with co- and cross-circularly polarized pump and probe presents different strength at several picosecond delay time...
March 21, 2017: Scientific Reports
Guoyang Yu, Yangyang Zeng, Wencan Guo, Honglin Wu, Gangbei Zhu, Zhaoyang Zheng, Xianxu Zheng, Yunfei Song, Yanqiang Yang
The femtosecond time-resolved multiplex coherent anti-Stokes Raman scattering (CARS) technique has been performed to investigate the intramolecular vibrational redistribution (IVR) through vibrational couplings in RDX molecules. In the multiplex CARS experiment, the supercontinuum (SC) was used as broadband Stokes light to coherently and collectively excite multiple vibrational modes, and quantum beats arising from vibrational couplings among these modes were observed. The IVR of RDX is visualized by a topological graph of these vibrational couplings...
March 20, 2017: Journal of Physical Chemistry. A
Zahra Haghshenasfard, Michael G Cottam
A microscopic (Hamiltonian-based) method for the quantum statistics of bosonic excitations in a two-mode magnon system is developed. Both the exchange and the dipole-dipole interactions, as well as the Zeeman term for an external applied field, are included in the spin Hamiltonian, and the model also contains the nonlinear effects due to parallel pumping and four-magnon interactions. The quantization of spin operators is achieved through the Holstein-Primakoff formalism, and then a coherent magnon state representation is used to study the occupation magnon number and the quantum statistical behaviour of the system...
March 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Markus F Weber, Erwin Frey
This review provides a pedagogic and self-contained introduction to master equations and to their representation by path integrals. Since the 1930s, master equations have served as a fundamental tool to understand the role of fluctuations in complex biological, chemical, and physical systems. Despite their simple appearance, analyses of master equations most often rely on low-noise approximations such as the Kramers-Moyal or the system size expansion, or require ad-hoc closure schemes for the derivation of low-order moment equations...
April 2017: Reports on Progress in Physics
Forough Ebrahimi, Baharudin Ibrahim, Chin-Hoe Teh, Vikneswaran Murugaiyah, Kit-Lam Chan
Male infertility is one of the leading causes of infertility which affects many couples worldwide. Semen analysis is a routine examination of male fertility status which is usually performed on semen samples obtained through masturbation that may be inconvenient to patients. Eurycoma longifolia (Tongkat Ali, TA), native to Malaysia, has been traditionally used as a remedy to boost male fertility. In our recent studies in rats, upon the administration of high-quassinoid content extracts of TA including TA water (TAW), quassinoid-rich TA (TAQR) extracts, and a low-quassinoid content extract including quassinoid-poor TA (TAQP) extract, sperm count (SC) increased in TAW- and TAQR-treated rats when compared to the TAQP-treated and control groups...
March 17, 2017: Systems Biology in Reproductive Medicine
Uta Meyer, Géraldine Haack, Christoph Groth, Xavier Waintal
The oscillatory interlayer exchange interaction between two magnetic layers separated by a metallic spacer is one of the few coherent quantum phenomena that persists at room temperature. Here, we show that this interaction can be controlled dynamically by illuminating the sample (e.g., a spin valve) with radiation in the 10-100 THz range. We predict that the exchange interaction can be changed from ferromagnetic to antiferromagnetic (and vice versa) by tuning the amplitude and/or the frequency of the radiation...
March 3, 2017: Physical Review Letters
Stine T Olsen, Thorsten Hansen, Kurt V Mikkelsen
Electron transport through a molecule is often described in one of the two regimes: the coherent tunnelling regime or the Coulomb blockade regime. The twilight zone of the two regimes still possesses many unsolved questions. A theoretical analysis of the oligophenylenevinylene OPV3 experiments by Bjørnholm and co-workers is performed. The experiments showed how two OPV3 derivatives performed very differently despite the strong similarity of the molecular structure, hence the experimental data showed two different transport mechanisms...
March 14, 2017: Journal of Chemical Physics
K Mouloudakis, I K Kominis
Radical-ion-pair reactions, central for understanding the avian magnetic compass and spin transport in photosynthetic reaction centers, were recently shown to be a fruitful paradigm of the new synthesis of quantum information science with biological processes. We show here that the master equation so far constituting the theoretical foundation of spin chemistry violates fundamental bounds for the entropy of quantum systems, in particular the Ozawa bound. In contrast, a recently developed theory based on quantum measurements, quantum coherence measures, and quantum retrodiction, thus exemplifying the paradigm of quantum biology, satisfies the Ozawa bound as well as the Lanford-Robinson bound on information extraction...
February 2017: Physical Review. E
Y H Hsieh, Y T Yu, P H Tuan, J C Tung, K F Huang, Y F Chen
The trajectory equations for classical periodic orbits in the equilateral-triangular and circular billiards are systematically extracted from quantum stationary coherent states. The relationship between the phase factors of quantum stationary coherent states and the initial positions of classical periodic orbits is analytically derived. In addition, the stationary coherent states with noncoprime parametric numbers are shown to correspond to the multiple periodic orbits, which cannot be explicable in the one-particle picture...
February 2017: Physical Review. E
Yang Zhang, G Luca Celardo, Fausto Borgonovi, Lev Kaplan
We study quantum enhancement of transport in open systems in the presence of disorder and dephasing. Quantum coherence effects may significantly enhance transport in open systems even in the semiclassical regime (where the decoherence rate is greater than the intersite hopping amplitude), as long as the disorder is sufficiently strong. When the strengths of disorder and dephasing are fixed, there is an optimal opening strength at which the coherent transport enhancement is optimized. Analytic results are obtained in two simple paradigmatic tight-binding models of large systems: the linear chain and the fully connected network...
February 2017: Physical Review. E
Tatsuro Yuge, Makoto Yamaguchi, Tetsuo Ogawa
We investigate energy transfer by the radiation from a cavity quantum electrodynamics system in the context of quantum thermodynamics. We propose a method of decomposing it into work and heat within the framework of quantum master equations. We find that the work and heat correspond, respectively, to the coherent and incoherent parts of the radiation. In the derivation of the method, it is crucial to investigate the dynamics of the system that receives the radiation from the cavity.
February 2017: Physical Review. E
Tatsuhiko N Ikeda, Takashi Mori, Eriko Kaminishi, Masahito Ueda
Entanglement prethermalization (EP) refers to a quasi-stationary nonequilibrium state of a composite system in which each individual subsystem looks thermal but the entire system remains nonthermal due to quantum entanglement between subsystems. We theoretically study the dynamics of EP following a coherent split of a one-dimensional harmonic potential in which two interacting bosons are confined. This problem is equivalent to that of an interaction quench between two harmonic oscillators. We show that this simple model captures the bare essentials of EP; that is, each subsystem relaxes to an approximate thermal equilibrium, whereas the total system remains entangled...
February 2017: Physical Review. E
Xiaoqing Tu, Guangai Sun, Jian Gong, Lijuan Liu, Yong Ren, Penglin Gao, Wenzhao Wang, H Yan
Due to quantum coherence, nanoparticles have very large cross sections when scattering with very cold or Ultracold Neutrons (UCN). By calculating the scattering cross section quantum mechanically at first, then treating the nanoparticles as classical objects when including the rotational effects, we can derive the associated energy transfer. We find that rotational effects could play an important role in slowing down UCN. In consequence, the slowing down efficiency can be improved by as much as ~40%. Since thermalization of neutrons with the moderator requires typically hundreds of collisions between them, a ~40% increase of the efficiency per collision could have a significant effect...
March 15, 2017: Scientific Reports
L Debora Contreras-Pulido, Martin Bruderer
One of the fundamental questions in quantum transport is how charge transfer through complex nanostructures is influenced by quantum coherence. We address this issue for linear triple quantum dots by comparing a Lindblad density matrix description with a Pauli rate equation approach and analyze the corresponding zero-frequency counting statistics of charge transfer. The impact of decaying coherences of the density matrix due to dephasing is also studied. Our findings reveal that the sensitivity to coherence shown by shot noise and skewness, in particular in the limit of large coupling to the drain reservoir, can be used to unambiguously evidence coherent processes involved in charge transport across triple quantum dots...
March 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Tobias Fredrik Sjolander, Michael C D Tayler, Arne Kentner, Dmitry Budker, Alexander Pines
We present a two-dimensional method for obtaining (13)C-decoupled, (1)H-coupled Nuclear Magnetic Resonance (NMR) spectra in zero magnetic field using coherent spin-decoupling. The result is a spectrum determined only by the proton-proton J-coupling network. Detection of NMR signals in zero magnetic field requires at least two different nuclear spin species but the proton J-spectrum is independent of isotopomer, potentially simplifying spectra and thereby improving the analytical capabilities of zero-field NMR...
March 14, 2017: Journal of Physical Chemistry Letters
Tao Li, Qiang Zeng, Xinbing Song, Xiangdong Zhang
The Klyachko, Can, Binicioglu, and Shumovsky (KCBS) inequality is an important contextuality inequality in three-level system, which has been demonstrated experimentally by using quantum states. Using the path and polarization degrees of freedom of classical optics fields, we have constructed the classical trit (cetrit), tested the KCBS inequality and its geometrical form (Wright's inequality) in this work. The projection measurement has been implemented, the clear violations of the KCBS inequality and its geometrical form have been observed...
March 14, 2017: Scientific Reports
Qi Gao, Gordon R Chalmers, Kelley W Moremen, James H Prestegard
Sparse isotopic labeling of proteins for NMR studies using single types of amino acid ((15)N or (13)C enriched) has several advantages. Resolution is enhanced by reducing numbers of resonances for large proteins, and isotopic labeling becomes economically feasible for glycoproteins that must be expressed in mammalian cells. However, without access to the traditional triple resonance strategies that require uniform isotopic labeling, NMR assignment of crosspeaks in heteronuclear single quantum coherence (HSQC) spectra is challenging...
March 13, 2017: Journal of Biomolecular NMR
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