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Quantum coherence

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
Jesse D Marshall, Jin Zhong Li, Yanping Zhang, Yiyang Gong, François St-Pierre, Michael Z Lin, Mark J Schnitzer
Electrophysiological field potential dynamics are of fundamental interest in basic and clinical neuroscience, but how specific cell types shape these dynamics in the live brain is poorly understood. To empower mechanistic studies, we created an optical technique, TEMPO, that records the aggregate trans-membrane voltage dynamics of genetically specified neurons in freely behaving mice. TEMPO has >10-fold greater sensitivity than prior fiber-optic techniques and attains the noise minimum set by quantum mechanical photon shot noise...
December 1, 2016: Cell
Kosuke Kakuyanagi, Yuichiro Matsuzaki, Corentin Déprez, Hiraku Toida, Kouichi Semba, Hiroshi Yamaguchi, William J Munro, Shiro Saito
The hybridization of distinct quantum systems is now seen as an effective way to engineer the properties of an entire system leading to applications in quantum metamaterials, quantum simulation, and quantum metrology. Recent improvements in both fabrication techniques and qubit design have allowed the community to consider coupling large ensembles of artificial atoms, such as superconducting qubits, to a resonator. Here, we demonstrate the coherent coupling between a microwave resonator and a macroscopic ensemble composed of several thousand superconducting flux qubits, where we observe a large dispersive frequency shift in the spectrum of 250 MHz...
November 18, 2016: Physical Review Letters
Michael Förster, Timo Paschen, Michael Krüger, Christoph Lemell, Georg Wachter, Florian Libisch, Thomas Madlener, Joachim Burgdörfer, Peter Hommelhoff
We demonstrate coherent control of multiphoton and above-threshold photoemission from a single solid-state nanoemitter driven by a fundamental and a weak second harmonic laser pulse. Depending on the relative phase of the two pulses, electron emission is modulated with a contrast of the oscillating current signal of up to 94%. Electron spectra reveal that all observed photon orders are affected simultaneously and similarly. We confirm that photoemission takes place within 10 fs. Accompanying simulations indicate that the current modulation with its large contrast results from two interfering quantum pathways leading to electron emission...
November 18, 2016: Physical Review Letters
Kuniyoshi Shimizu, Yhiya M Amen, Satoru Kaifuchi
Ganoderma lingzhi is one of the most famous medicinal fungi in the world. It has been used in folk medicine, especially in East Asian countries. It is also a white-rot fungus with strong wood degradation ability, especially against lignin. Different classes of bioactive natural products have been reported in Ganoderma, including triterpenes, polysaccharides, sterols, and peptides. The triterpenes and polysaccharides are the primary bioactive compounds of Ganoderma. We report for the first time the presence of 3 methoxyflavones as minor constituents in G...
2016: International Journal of Medicinal Mushrooms
Hou-Dao Zhang, Qin Qiao, Rui-Xue Xu, YiJing Yan
In this work, we study the effects of non-Condon vibronic coupling on the quantum coherence of excitation energy transfer, via the exact dissipaton-equation-of-motion evaluations on excitonic model systems. Field-triggered excitation energy transfer dynamics and two dimensional coherent spectroscopy are simulated for both Condon and non-Condon vibronic couplings. Our results clearly demonstrate that the non-Condon vibronic coupling intensifies the dynamical electronic-vibrational energy transfer and enhances the total system-and-bath quantum coherence...
November 28, 2016: Journal of Chemical Physics
Yoon-Seok Lee, Sang Min Lee, Heonoh Kim, Han Seb Moon
We report a bright photon-pair source with a coincidence counting rate per input power (cps/mW) of tens of thousands, obtained via spontaneous four-wave mixing from a Doppler-broadened atomic ensemble of the 5S<sub>1/2</sub>-5P<sub>3/2</sub>-5D<sub>5/2</sub> transition of <sup>87</sup>Rb. The photon-pair generation rate is enhanced by the two-photon coherence contributions from almost all the atomic velocity groups in the Doppler-broadened ladder-type atomic system...
November 28, 2016: Optics Express
Lukáš Lachman, Radim Filip
Quantum attributes of light have been related to non-classicality so far, i. e. to incompatibility with mixtures of coherent states. The progress in quantum optics indicates that this feature does not suffice to witness exotic behavior of light. Contrary, quantum non-Gaussianity is starting to appear as a promising and applicable property reflecting interesting states of light that are suitable for quantum protocols. We investigate a newly introduced hierarchy of criteria of quantum non-Gaussianity and predict this attribute can be observed on light emitted from many single photon emitters, even if the light undergoes realistic optical losses...
November 28, 2016: Optics Express
Ari T Friberg, Tero Setälä
The coherence theory of random, vector-valued optical fields has been of great research interest in recent years. In this work we formulate the foundations of electromagnetic coherence theory both in the space-time and space-frequency domains, with particular emphasis on various types of optical interferometry. Analyzing statistically stationary, two-component (paraxial) electric fields in the classical and quantum-optical contexts we show fundamental connections between the conventional (polarization) Stokes parameters and the associated two-point (coherence) Stokes parameters...
December 1, 2016: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Yun Zhu, Minyu Chen, Yixin Zhang, Ye Li
This study investigates the effect of the anisotropic non-Kolmogorov turbulence of the marine atmosphere on propagation of orbital angular momentum (OAM) modes carried by partially coherent modified Bessel-Gaussian (PCMBG) beams. The analytic formula of the probability density of OAM modes is derived and used to explore the evolution of the received power of the OAM mode. PCMBG beams with long wavelength, low quantum number of the OAM mode, and a high spectral degree of coherence of the source are robust for the OAM mode propagation in turbulence...
December 1, 2016: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Zhen Qu, Ivan B Djordjevic, Mark A Neifeld
We theoretically investigate and experimentally demonstrate a RF-assisted four-state continuous-variable quantum key distribution (CV-QKD) system. Classical coherent detection is implemented with a simple digital phase noise cancelation scheme. In the proposed system, there is no need for frequency and phase locking between the quantum signals and the local oscillator laser. Moreover, in principle, there is no residual phase noise, and a mean excess noise of 0.0115 (in shot-noise units) can be acquired experimentally...
December 1, 2016: Optics Letters
J Brus, J Czernek, M Urbanova, L Kobera, A Jegorov
The difficulty in the prediction of the complicated solid-state structure of boronic acid derivatives, resulting from the complex pathway of reversible covalent interactions, represents a significant obstacle to the development of a new generation of advanced supramolecular systems such as covalent organic frameworks of efficient anticancer drugs. In this contribution, various 2D (11)B-(11)B solid-state NMR correlation techniques supported by DFT calculations were explored to formulate a reliable tool for monitoring the covalent assembly of boronic acid residues in the solid state...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
Moumita Dutta, Soutik Betal, Xomalin G Peralta, Amar S Bhalla, Ruyan Guo
Phase modulators are one of the key components of many applications in electromagnetic and opto-electric wave propagations. Phase-shifters play an integral role in communications, imaging and in coherent material excitations. In order to realize the terahertz (THz) electromagnetic spectrum as a fully-functional bandwidth, the development of a family of efficient THz phase modulators is needed. Although there have been quite a few attempts to implement THz phase modulators based on quantum-well structures, liquid crystals, or meta-materials, significantly improved sensitivity and dynamic control for phase modulation, as we believe can be enabled by piezoelectric-resonance devices, is yet to be investigated...
November 30, 2016: Scientific Reports
Zahra Haghshenasfard, Michael G Cottam
Theoretical studies are reported for the statistical properties of a microwave-driven interacting magnon system. Both the magnetic dipole-dipole and the exchange interactions are included and the theory is developed for the case of parallel pumping allowing for the inclusion of the nonlinear processes due to the four-magnon interactions. The method of second quantization is used to transform the total Hamiltonian from spin operators to boson creation and annihilation operators. By using the coherent magnon state representation we have studied the magnon occupation number and the statistical behavior of the system...
February 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yulan Lin, Pieter E S Smith, Zhiyong Zhang, Lucio Frydman
Multidimensional Nuclear Magnetic Resonance (NMR) provides a unique window into structure and dynamics at an atomic level. Traditionally, given the scan-by-scan time modulation involved in these experiments, the duration of nD NMR increases exponentially with spectral dimensionality. In addition, acquisition times increase as the number of spectral elements being sought in each indirect domain - given by the ratio between the spectral bandwidth being targeted and the resolution desired. These long sampling times can be substantially reduced by exploiting information that is often available from lower-dimensionality acquisitions...
November 21, 2016: Journal of Magnetic Resonance
Po-Chen Kuo, Guang-Yin Chen, Yueh-Nan Chen
Coherent scatterings of surface plasmons coupled to quantun dots have attracted great attention in plasmonics. Recently, an experiment has shown that the quantum dots located nearby a nanowire can be separated not only in distance, but also an angle ϕ along the cylindrical direction. Here, by using the real-space Hamiltonian and the transfer matrix method, we analytically obtain the transmission/reflection spectra of nanowire surface plasmons coupled to quantum dots with an azimuthal angle difference. We find that the scattering spectra can show completely different features due to different positions and azimuthal angles of the quantum dots...
November 28, 2016: Scientific Reports
Samuel F Cousin, Cyril Charlier, Pavel Kadeřávek, Thorsten Marquardsen, Jean-Max Tyburn, Pierre-Alain Bovier, Simone Ulzega, Thomas Speck, Dirk Wilhelm, Frank Engelke, Werner Maas, Dimitrios Sakellariou, Geoffrey Bodenhausen, Philippe Pelupessy, Fabien Ferrage
Nuclear magnetic resonance (NMR) is a ubiquitous branch of spectroscopy that can explore matter at the scale of an atom. Significant improvements in sensitivity and resolution have been driven by a steady increase of static magnetic field strengths. However, some properties of nuclei may be more favourable at low magnetic fields. For example, transverse relaxation due to chemical shift anisotropy increases sharply at higher magnetic fields leading to line-broadening and inefficient coherence transfers. Here, we present a two-field NMR spectrometer that permits the application of rf-pulses and acquisition of NMR signals in two magnetic centres...
November 28, 2016: Physical Chemistry Chemical Physics: PCCP
Zhong-Xiao Wang, Shuhao Wang, Teng Ma, Tie-Jun Wang, Chuan Wang
The generation and quantification of quantum entanglement is crucial for quantum information processing. Here we study the transition of Gaussian correlation under the effect of linear optical beam-splitters. We find the single-mode Gaussian coherence acts as the resource in generating Gaussian entanglement for two squeezed states as the input states. With the help of consecutive beam-splitters, single-mode coherence and quantum entanglement can be converted to each other. Our results reveal that by using finite number of beam-splitters, it is possible to extract all the entanglement from the single-mode coherence even if the entanglement is wiped out before each beam-splitter...
November 28, 2016: Scientific Reports
S Abend, M Gebbe, M Gersemann, H Ahlers, H Müntinga, E Giese, N Gaaloul, C Schubert, C Lämmerzahl, W Ertmer, W P Schleich, E M Rasel
We demonstrate a quantum gravimeter by combining the advantages of an atom chip for the generation, delta-kick collimation, and coherent manipulation of freely falling Bose-Einstein condensates (BECs) with an innovative launch mechanism based on Bloch oscillations and double Bragg diffraction. Our high-contrast BEC interferometer realizes tens of milliseconds of free fall in a volume as little as a one centimeter cube and paves the way for measurements with sub-μGal accuracies in miniaturized, robust devices...
November 11, 2016: Physical Review Letters
Qi Zhang, Yongrui Wang, Weilu Gao, Zhongqu Long, John D Watson, Michael J Manfra, Alexey Belyanin, Junichiro Kono
We have performed time-resolved terahertz absorption measurements on photoexcited electron-hole pairs in undoped GaAs quantum wells in magnetic fields. We probed both unbound- and bound-carrier responses via cyclotron resonance and intraexciton resonance, respectively. The stability of excitons, monitored as the pair density was systematically increased, was found to dramatically increase with increasing magnetic field. Specifically, the 1s-2p_{-} intraexciton transition at 9 T persisted up to the highest density, whereas the 1s-2p feature at 0 T was quickly replaced by a free-carrier Drude response...
November 11, 2016: Physical Review Letters
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