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Zero Quantum Coherence

Minhaeng Cho
Parametric down-conversion is a second-order nonlinear optical process annihilating a pump photon and creating a pair of photons in the signal and idler modes. Then, by using two parametric down-converters and introducing a path indistinguishability for the two generated idler modes, a quantum coherence between two conjugate signal beams can be induced. Such a double spontaneous or stimulated parametric down-conversion scheme has been used to demonstrate quantum spectroscopy and imaging with undetected idler photons via measuring one-photon interference between their correlated signal beams...
May 14, 2018: Journal of Chemical Physics
Mangesh Bhattarai, Vineet Bharti, Vasant Natarajan
We demonstrate a technique for continuous tuning of the Hanle effect from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) by changing the polarization ellipticity of a control beam. In contrast to previous work in this field, we use spatially separated probe and control beams. The experiments are done using magnetic sublevels of the Fg  = 4 → Fe  = 5 closed hyperfine transition in the 852 nm D2 line of 133 Cs. The atoms are contained in a room temperature vapor cell with anti-relaxation (paraffin) coating on the walls...
May 14, 2018: Scientific Reports
Hyukjoon Kwon, Hyunseok Jeong, David Jennings, Benjamin Yadin, M S Kim
In thermodynamics, quantum coherences-superpositions between energy eigenstates-behave in distinctly nonclassical ways. Here we describe how thermodynamic coherence splits into two kinds-"internal" coherence that admits an energetic value in terms of thermodynamic work, and "external" coherence that does not have energetic value, but instead corresponds to the functioning of the system as a quantum clock. For the latter form of coherence, we provide dynamical constraints that relate to quantum metrology and macroscopicity, while for the former, we show that quantum states exist that have finite internal coherence yet with zero deterministic work value...
April 13, 2018: Physical Review Letters
Jakob Petersen, Eli Pollak
The time it takes a particle to tunnel through the asymmetric Eckart barrier potential is investigated using Gaussian wavepackets, where the barrier serves as a model for the potential along a chemical reaction coordinate. We have previously shown that the, in principle experimentally measurable, tunneling flight time, which determines the time taken by the transmitted particle to traverse the barrier, vanishes for symmetric potentials like the Eckart and square barrier [ Petersen , J. ; Pollak , E. J. Phys...
April 12, 2018: Journal of Physical Chemistry. A
Kosmas L Tsakmakidis, Pankaj K Jha, Yuan Wang, Xiang Zhang
Self-organized criticality emerges in dynamical complex systems driven out of equilibrium and characterizes a wide range of classical phenomena in physics, geology, and biology. We report on a quantum coherence-controlled self-organized critical transition observed in the light localization behavior of a coherence-driven nanophotonic configuration. Our system is composed of a gain-enhanced plasmonic heterostructure controlled by a coherent drive, in which photons close to the stopped-light regime interact in the presence of the active nonlinearities, eventually synchronizing their dynamics...
March 2018: Science Advances
Stefan T Jagsch, Noelia Vico Triviño, Frederik Lohof, Gordon Callsen, Stefan Kalinowski, Ian M Rousseau, Roy Barzel, Jean-François Carlin, Frank Jahnke, Raphaël Butté, Christopher Gies, Axel Hoffmann, Nicolas Grandjean, Stephan Reitzenstein
Exploring the limits of spontaneous emission coupling is not only one of the central goals in the development of nanolasers, it is also highly relevant regarding future large-scale photonic integration requiring energy-efficient coherent light sources with a small footprint. Recent studies in this field have triggered a vivid debate on how to prove and interpret lasing in the high-β regime. We investigate close-to-ideal spontaneous emission coupling in GaN nanobeam lasers grown on silicon. Such nanobeam cavities allow for efficient funneling of spontaneous emission from the quantum well gain material into the laser mode...
February 8, 2018: Nature Communications
Junwen Zeng, Erfu Liu, Yajun Fu, Zhuoyu Chen, Chen Pan, Chenyu Wang, Miao Wang, Yaojia Wang, Kang Xu, Songhua Cai, Xingxu Yan, Yu Wang, Xiaowei Liu, Peng Wang, Shi-Jun Liang, Yi Cui, Harold Y Hwang, Hongtao Yuan, Feng Miao
Layered metal chalcogenide materials provide a versatile platform to investigate emergent phenomena and two-dimensional (2D) superconductivity at/near the atomically thin limit. In particular, gate-induced interfacial superconductivity realized by the use of an electric-double-layer transistor (EDLT) has greatly extended the capability to electrically induce superconductivity in oxides, nitrides, and transition metal chalcogenides and enable one to explore new physics, such as the Ising pairing mechanism. Exploiting gate-induced superconductivity in various materials can provide us with additional platforms to understand emergent interfacial superconductivity...
February 14, 2018: Nano Letters
Frederico Martins, Filip K Malinowski, Peter D Nissen, Saeed Fallahi, Geoffrey C Gardner, Michael J Manfra, Charles M Marcus, Ferdinand Kuemmeth
We use a one-electron quantum dot as a spectroscopic probe to study the spin properties of a gate-controlled multielectron GaAs quantum dot at the transition between odd and even occupation numbers. We observe that the multielectron ground-state transitions from spin-1/2-like to singletlike to tripletlike as we increase the detuning towards the next higher charge state. The sign reversal in the inferred exchange energy persists at zero magnetic field, and the exchange strength is tunable by gate voltages and in-plane magnetic fields...
December 1, 2017: Physical Review Letters
Sutirtha N Chowdhury, Pengfei Huo
We introduce the coherent-state mapping ring polymer molecular dynamics (CS-RPMD), a new method that accurately describes electronic non-adiabatic dynamics with explicit nuclear quantization. This new approach is derived by using coherent-state mapping representation for the electronic degrees of freedom (DOF) and the ring-polymer path-integral representation for the nuclear DOF. The CS-RPMD Hamiltonian does not contain any inter-bead coupling term in the state-dependent potential and correctly describes electronic Rabi oscillations...
December 7, 2017: Journal of Chemical Physics
Yahya Alavirad, David Clarke, Amit Nag, Jay D Sau
Parafermionic zero modes are a novel set of excitations displaying non-Abelian statistics somewhat richer than that of Majorana modes. These modes are predicted to occur when nearby fractional quantum Hall edge states are gapped by an interposed superconductor. Despite substantial experimental progress, we argue that the necessary crossed Andreev reflection in this arrangement is a challenging milestone to reach. We propose a superconducting quantum dot array structure on a fractional quantum Hall edge that can lead to parafermionic zero modes from coherent superconducting forward scattering on a quantum Hall edge...
November 24, 2017: Physical Review Letters
Chandrashekar Radhakrishnan, Manikandan Parthasarathy, Segar Jambulingam, Tim Byrnes
We study quantum coherence in a spin chain with both symmetric exchange and antisymmetric Dzyaloshinsky-Moriya couplings. Quantum coherence is quantified using the recently introduced quantum Jensen-Shannon divergence, which has the property that it is easily calculable and has several desirable mathematical properties. We calculate exactly the coherence for arbitrary number of spins at zero temperature in various limiting cases. The σz σz interaction tunes the amount of coherence in the system, and the antisymmetric coupling changes the nature of the coherence...
October 24, 2017: Scientific Reports
Alberto Cappellaro, Tommaso Macrì, Giovanni F Bertacco, Luca Salasnich
Laser induced transitions between internal states of atoms have been playing a fundamental role to manipulate atomic clouds for many decades. In absence of interactions each atom behaves independently and their coherent quantum dynamics is described by the Rabi model. Since the experimental observation of Bose condensation in dilute gases, static and dynamical properties of multicomponent quantum gases have been extensively investigated. Moreover, at very low temperatures quantum fluctuations crucially affect the equation of state of many-body systems...
October 17, 2017: Scientific Reports
Sergej Markmann, Hanond Nong, Shovon Pal, Tobias Fobbe, Negar Hekmat, Reshma A Mohandas, Paul Dean, Lianhe Li, Edmund H Linfield, A Giles Davies, Andreas D Wieck, Nathan Jukam
Two-dimensional spectroscopy is performed on a terahertz (THz) frequency quantum cascade laser (QCL) with two broadband THz pulses. Gain switching is used to amplify the first THz pulse and the second THz pulse is used to probe the system. Fourier transforms are taken with respect to the delay time between the two THz pulses and the sampling time of the THz probe pulse. The two-dimensional spectrum consists of three peaks at (ωτ = 0, ωt = ω0 ), (ωτ = ω0 , ωt = ω0 ), and (ωτ = 2ω0 , ωt = ω0 ) where ω0 denotes the lasing frequency...
September 4, 2017: Optics Express
B L Green, S Mottishaw, B G Breeze, A M Edmonds, U F S D'Haenens-Johansson, M W Doherty, S D Williams, D J Twitchen, M E Newton
We demonstrate optical spin polarization of the neutrally charged silicon-vacancy defect in diamond (SiV^{0}), an S=1 defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but nonzero at below-resonant energies. We measure an ensemble spin coherence time T_{2}>100  μs at low-temperature, and a spin relaxation limit of T_{1}>25  s. Optical spin-state initialization around 946 nm allows independent initialization of SiV^{0} and NV^{-} within the same optically addressed volume, and SiV^{0} emits within the telecoms down-conversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that SiV^{0} is a promising candidate for a long-range quantum communication technology...
September 1, 2017: Physical Review Letters
A N Pravdivtsev, A V Yurkovskaya, P A Petrov, H-M Vieth
A consistent theoretical description of the spin dynamics underlying photo-PHIP (para-hydrogen induced polarization) experiments is given and validated experimentally: spectra from zero-quantum coherence (ZQC) "in-phase" and "out-of-phase" were obtained and evolution of ZQCs and the population of singlet spin state was tracked and modeled. Data from recent literature [O. Torres et al., J. Am. Chem. Soc., 2014] are reinterpreted. Advantages of using M2S sequences such as APSOC for detecting photo-PHIP are demonstrated...
October 4, 2017: Physical Chemistry Chemical Physics: PCCP
Zheng-Yang Zhou, Mi Chen, Lian-Ao Wu, Ting Yu, J Q You
Dark state as a consequence of interference between different quantum states has great importance in the fields of chip-scale atomic clock and quantum information. For the Λ-type three-level system, this dark state is generally regarded as being dissipation-free because it is a superposition of two lowest states without dipole transition between them. However, previous studies are based on the rotating-wave approximation (RWA) by neglecting the counter-rotating terms in the system-environment interaction. In this work, we study non-Markovian quantum dynamics of the dark state in a Λ-type three-level system coupled to two bosonic baths and reveal the effect of counter-rotating terms on the dark state...
July 24, 2017: Scientific Reports
R Jayaprakash, F G Kalaitzakis, G Christmann, K Tsagaraki, M Hocevar, B Gayral, E Monroy, N T Pelekanos
Polariton lasers are coherent light sources based on the condensation of exciton-polaritons in semiconductor microcavities, which occurs either in the kinetic or thermodynamic (Bose-Einstein) regime. Besides their fundamental interest, polariton lasers have the potential of extremely low operating thresholds. Here, we demonstrate ultra-low threshold polariton lasing at room temperature, using an all-dielectric, GaN membrane-based microcavity, with a spontaneously-formed zero-dimensional trap. The microcavity is fabricated using an innovative method, which involves photo-electrochemical etching of an InGaN sacrificial layer and allows for the incorporation of optimally-grown GaN active quantum wells inside a cavity with atomically-smooth surfaces...
July 17, 2017: Scientific Reports
Tomasz Jakubczyk, Valentin Delmonte, Sarah Fischbach, Daniel Wigger, Doris E Reiter, Quentin Mermillod, Peter Schnauber, Arsenty Kaganskiy, Jan-Hindrik Schulze, André Strittmatter, Sven Rodt, Wolfgang Langbein, Tilmann Kuhn, Stephan Reitzenstein, Jacek Kasprzak
Optimized light-matter coupling in semiconductor nanostructures is a key to understand their optical properties and can be enabled by advanced fabrication techniques. Using in situ electron beam lithography combined with a low-temperature cathodoluminescence imaging, we deterministically fabricate microlenses above selected InAs quantum dots (QDs), achieving their efficient coupling to the external light field. This enables performing four-wave mixing microspectroscopy of single QD excitons, revealing the exciton population and coherence dynamics...
December 21, 2016: ACS Photonics
Daniel D Powell, Michael R Wasielewski, Mark A Ratner
Coherence effects on electron transfer in a series of symmetric and asymmetric two-, three-, four-, and five-site molecular model systems for photosystem I in cyanobacteria and green plants were studied. The total site energies of the electronic Hamiltonian were calculated using the density functional theory (DFT) formalism and included the zero point vibrational energies of the electron donors and acceptors. Site energies and couplings were calculated using a polarizable continuum model to represent various solvent environments, and the site-to-site couplings were calculated using fragment charge difference methods at the DFT level of theory...
July 27, 2017: Journal of Physical Chemistry. B
Le Zhang, Andrew McCallister, Karl M Koshlap, Rosa Tamara Branca
PURPOSE: Because the resonance frequency of water-fat intermolecular zero-quantum coherences (iZQCs) reflects the water-fat frequency separation at the microscopic scale, these frequencies have been proposed and used as a mean to obtain more accurate temperature information. The purpose of this work was to investigate the dependence of the water-fat iZQC resonance frequency on sample microstructure and on the specific choice of the correlation distance. METHODS: The effect of water-fat susceptibility gradients on the water-methylene iZQC resonance frequency was first computed and then measured for different water-fat emulsions and for a mixture of porcine muscle and fat...
March 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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