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Quantum coherence

Gijs van Erven, Ries de Visser, Donny W H Merkx, Willem Strolenberg, Peter De Gijsel, Harry Gruppen, Mirjam A Kabel
Understanding mechanisms underlying plant biomass recalcitrance at molecular level can only be achieved by accurate analyses of both content and structural features of the molecules involved. Current quantification of lignin is, however, majorly based on unspecific gravimetric analysis after sulphuric acid hydrolysis. Hence, our research aimed at specific lignin quantification with concurrent characterization of its structural features. Hereto, for the first time, a polymeric (13)C lignin was used as internal standard (IS) for lignin quantification via analytical pyrolysis coupled to gas chromatography with mass-spectrometric detection in selected ion monitoring mode (py-GC-SIM-MS)...
September 19, 2017: Analytical Chemistry
Kai Hao, Lixiang Xu, Fengcheng Wu, Philipp Nagler, Kha Tran, Xin Ma, Christian Schüller, Tobias Korn, Allan H MacDonald, Galan Moody, Xiaoqin Li
The emerging field of valleytronics aims to exploit the valley pseudospin of electrons residing near Bloch band extrema as an information carrier. Recent experiments demonstrating optical generation and manipulation of exciton valley coherence (the superposition of electron-hole pairs at opposite valleys) in monolayer transition metal dichalcogenides (TMDs) provide a critical step towards control of this quantum degree of freedom. The charged exciton (trion) in TMDs is an intriguing alternative to the neutral exciton for control of valley pseudospin because of its long spontaneous recombination lifetime, its robust valley polarization, and its coupling to residual electronic spin...
June 2017: 2d Materials
Moritz Merklein, Birgit Stiller, Khu Vu, Stephen J Madden, Benjamin J Eggleton
Controlling and manipulating quanta of coherent acoustic vibrations-phonons-in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation...
September 18, 2017: Nature Communications
Alejandro D Somoza, Ke-Wei Sun, Rafael A Molina, Yang Zhao
Self-assembled supramolecular aggregates are excellent candidates for the design of efficient excitation transport devices. Both artificially prepared and natural photosynthetic aggregates in plants and bacteria present an important degree of disorder that is supposed to hinder excitation transport. Besides, molecular excitations couple to nuclear motion affecting excitation transport in a variety of ways. We present an exhaustive study of exciton dynamics in disordered nanorings with long-range interactions under the influence of a phonon bath taking the LH2 system of purple bacteria as a model...
September 18, 2017: Physical Chemistry Chemical Physics: PCCP
David Paleček, Petra Edlund, Sebastian Westenhoff, Donatas Zigmantas
Photosynthetic proteins have evolved over billions of years so as to undergo optimal energy transfer to the sites of charge separation. On the basis of spectroscopically detected quantum coherences, it has been suggested that this energy transfer is partially wavelike. This conclusion depends critically on the assignment of the coherences to the evolution of excitonic superpositions. We demonstrate that, for a bacterial reaction center protein, long-lived coherent spectroscopic oscillations, which bear canonical signatures of excitonic superpositions, are essentially vibrational excited-state coherences shifted to the ground state of the chromophores...
September 2017: Science Advances
Dmitry A Kalashnikov, Elizaveta V Melik-Gaykazyan, Alexey A Kalachev, Ye Feng Yu, Arseniy I Kuznetsov, Leonid A Krivitsky
Interaction of light with media often occurs with a femtosecond response time. Its measurement by conventional techniques requires the use of femtosecond lasers and sophisticated time-gated optical detection. Here we demonstrate that by exploiting quantum interference of entangled photons it is possible to measure the dephasing time of a resonant media on the femtosecond time scale (down to 100 fs) using accessible continuous wave laser and single-photon counting. We insert a sample in the Hong-Ou-Mandel interferometer and observe the modification of the two-photon interference pattern, which is driven by the coherent response of the medium, determined by the dephasing time...
September 13, 2017: Scientific Reports
Yu-Ming He, Jin Liu, Sebastian Maier, Monika Emmerling, Stefan Gerhardt, Marcelo Davanço, Kartik Srinivasan, Christian Schneider, Sven Höfling
Deterministic techniques enabling the implementation and engineering of bright and coherent solid-state quantum light sources are key for the reliable realization of a next generation of quantum devices. Such a technology, at best, should allow one to significantly scale up the number of implemented devices within a given processing time. In this work, we discuss a possible technology platform for such a scaling procedure, relying on the application of nanoscale quantum dot imaging to the pillar microcavity architecture, which promises to combine very high photon extraction efficiency and indistinguishability...
July 20, 2017: Optica
Galan Moody, Steven T Cundiff
Multi-dimensional coherent spectroscopy (MDCS) has become an extremely versatile and sensitive technique for elucidating the structure, composition, and dynamics of condensed matter, atomic, and molecular systems. The appeal of MDCS lies in its ability to resolve both individual-emitter and ensemble-averaged dynamics of optically created excitations in disordered systems. When applied to semiconductors, MDCS enables unambiguous separation of homogeneous and inhomogeneous contributions to the optical linewidth, pinpoints the nature of coupling between resonances, and reveals signatures of many-body interactions...
2017: Adv Phys X
H Flentje, P-A Mortemousque, R Thalineau, A Ludwig, A D Wieck, C Bäuerle, T Meunier
Controlling nanocircuits at the single electron spin level is a possible route for large-scale quantum information processing. In this context, individual electron spins have been identified as versatile quantum information carriers to interconnect different nodes of a spin-based semiconductor quantum circuit. Despite extensive experimental efforts to control the electron displacement over long distances, maintaining electron spin coherence after transfer remained elusive up to now. Here we demonstrate that individual electron spins can be displaced coherently over a distance of 5 µm...
September 11, 2017: Nature Communications
Geon-Hyoung Park, Minsoo Kim, Kenji Watanabe, Takashi Taniguchi, Hu-Jong Lee
Recently, there has been significant interest in superconducting coherence via chiral quantum-Hall (QH) edge channels at an interface between a two-dimensional normal conductor and a superconductor (N-S) in a strong transverse magnetic field. In the field range where the superconductivity and the QH state coexist, the coherent confinement of electron- and hole-like quasiparticles by the interplay of Andreev reflection and the QH effect leads to the formation of Andreev edge states (AES) along the N-S interface...
September 8, 2017: Scientific Reports
Hélène Seiler, Samuel Palato, Patanjali Kambhampati
Ultrafast coherent multi-dimensional spectroscopies form a powerful set of techniques to unravel complex processes, ranging from light-harvesting, chemical exchange in biological systems to many-body interactions in quantum-confined materials. Yet these spectroscopies remain complex to implement at the high frequencies of vibrational and electronic transitions, thereby limiting their widespread use. Here we demonstrate the feasibility of two-dimensional spectroscopy at optical frequencies in a single beam. Femtosecond optical pulses are spectrally broadened to a relevant bandwidth and subsequently shaped into phase coherent pulse trains...
September 7, 2017: Journal of Chemical Physics
Chao Liu, Jinhong Liu, Junxiang Zhang, Shiyao Zhu
We present an interaction-free measurement with quantum Zeno effect and a high efficiency η = 74.6% ± 0.15%. As a proof-of-principle demonstration, this measurement can be used to implement a quantum counterfactual-like communication protocol. Instead of a single photon state, we use a coherent light as the input source and show that the output agrees with the proposed quantum counterfactual communication protocol according to Salih et al. Although the counterfactuality is not achieved due to the presence of a few photons in the public channel, we show that the signal light is nearly absent in the public channel, which exhibits a proof-of-principle quantum counterfactual-like property of communication...
September 7, 2017: Scientific Reports
Gabriele Barrera, Gabriele Alberto, Paola Tiberto, Gianmario Martra, Paolo Allia
Ultra-small magnetic particles containing Ni(2+) ions were grown at the surface of SiO2 spheroidal nanoparticles (typical diameter: 50 nm) starting from NiCl2 solutions. Depending on preparation details, two samples characterized by magnetic sub-nanostructures or lamellar sub-nanoparticles at the SiO2 nanosphere surface were obtained. The decorated SiO2 nanospheres were submitted to physico-chemical and magnetic characterization. In both samples, a magnetically blocked phase is observed at low temperature...
September 7, 2017: Scientific Reports
Christopher D M Hutchison, Violeta Cordon-Preciado, Rhodri M L Morgan, Takanori Nakane, Josie Ferreira, Gabriel Dorlhiac, Alvaro Sanchez-Gonzalez, Allan S Johnson, Ann Fitzpatrick, Clyde Fare, Jon P Marangos, Chun Hong Yoon, Mark S Hunter, Daniel P DePonte, Sébastien Boutet, Shigeki Owada, Rie Tanaka, Kensuke Tono, So Iwata, Jasper J van Thor
The photochromic fluorescent protein Skylan-NS (Nonlinear Structured illumination variant mEos3.1H62L) is a reversibly photoswitchable fluorescent protein which has an unilluminated/ground state with an anionic and cis chromophore conformation and high fluorescence quantum yield. Photo-conversion with illumination at 515 nm generates a meta-stable intermediate with neutral trans-chromophore structure that has a 4 h lifetime. We present X-ray crystal structures of the cis (on) state at 1.9 Angstrom resolution and the trans (off) state at a limiting resolution of 1...
September 7, 2017: International Journal of Molecular Sciences
Guilherme Tosi, Fahd A Mohiyaddin, Vivien Schmitt, Stefanie Tenberg, Rajib Rahman, Gerhard Klimeck, Andrea Morello
Practical quantum computers require a large network of highly coherent qubits, interconnected in a design robust against errors. Donor spins in silicon provide state-of-the-art coherence and quantum gate fidelities, in a platform adapted from industrial semiconductor processing. Here we present a scalable design for a silicon quantum processor that does not require precise donor placement and leaves ample space for the routing of interconnects and readout devices. We introduce the flip-flop qubit, a combination of the electron-nuclear spin states of a phosphorus donor that can be controlled by microwave electric fields...
September 6, 2017: Nature Communications
Jr-Shin Li, Justin Ruths, Steffen J Glaser
Designing accurate and high-fidelity broadband pulses is an essential component in conducting quantum experiments across fields from protein spectroscopy to quantum optics. However, constructing exact and analytic broadband pulses remains unsolved due to the nonlinearity and complexity of the underlying spin system dynamics. Here, we present a nontrivial dynamic connection between nonlinear spin and linear spring systems and show the surprising result that such nonlinear and complex pulse design problems are equivalent to designing controls to steer linear harmonic oscillators under optimal forcing...
September 5, 2017: Nature Communications
Qing Hu, Dafei Jin, Jun Xiao, Sang Hoon Nam, Xiaoze Liu, Yongmin Liu, Xiang Zhang, Nicholas X Fang
Two-dimensional molecular aggregate (2DMA), a thin sheet of strongly interacting dipole molecules self-assembled at close distance on an ordered lattice, is a fascinating fluorescent material. It is distinctively different from the conventional (single or colloidal) dye molecules and quantum dots. In this paper, we verify that when a 2DMA is placed at a nanometric distance from a metallic substrate, the strong and coherent interaction between the dipoles inside the 2DMA dominates its fluorescent decay at a picosecond timescale...
September 5, 2017: Proceedings of the National Academy of Sciences of the United States of America
Matthias Pfender, Nabeel Aslam, Patrick Simon, Denis Antonov, Gergö Thiering, Sina Burk, Felipe Fávaro de Oliveira, Andrej Denisenko, Helmut Fedder, Jan Meijer, José Antonio Garrido, Adam Gali, Tokuyuki Teraji, Junichi Isoya, Marcus W Doherty, Audrius Alkauskas, Alejandro Gallo, Andreas Grüneis, Philipp Neumann, Jörg Wrachtrup
In recent years, solid-state spin systems have emerged as promising candidates for quantum information processing. Prominent examples are the nitrogen-vacancy (NV) center in diamond, phosphorous dopants in silicon (Si:P), rare-earth ions in solids and VSi-centers in silicon-carbide. The Si:P system has demonstrated that its nuclear spins can yield exceedingly long spin coherence times by eliminating the electron spin of the dopant. For NV centers, however, a proper charge state for storage of nuclear spin qubit coherence has not been identified yet...
September 5, 2017: Nano Letters
Seokjun Hong, Minjae Lee, Yeong-Dae Kwon, Dong-Il Dan Cho, Taehyun Kim
Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 µm-thick dielectric layer and metal overhang structures atop the dielectric layer...
August 17, 2017: Journal of Visualized Experiments: JoVE
Takafumi Miyanaga, Takashi Azuhata, Kiyofumi Nitta, Shigefusa F Chichibu
The local structure around In atoms in an m-plane In0.06Ga0.94N film coherently grown on a freestanding m-plane GaN substrate was investigated by polarization-dependent X-ray absorption fine-structure. A step-by-step fitting procedure was proposed for the m-plane wurtzite structure. The interatomic distance for the first nearest neighbour In-N atomic pairs was almost isotropic. For the second nearest In-Ga pairs, the interatomic distances along the m- and a-axes were longer and shorter, respectively, than that in strain-free virtual crystals as expected for the m-plane compressive strain...
September 1, 2017: Journal of Synchrotron Radiation
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