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Zero Quantum Coherence

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https://www.readbyqxmd.com/read/28944791/coherent-evolution-of-singlet-spin-states-in-photo-phip-and-m2s-experiments
#1
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...
September 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28740187/dark-state-with-counter-rotating-dissipative-channels
#2
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
https://www.readbyqxmd.com/read/28717162/ultra-low-threshold-polariton-lasing-at-room-temperature-in-a-gan-membrane-microcavity-with-a-zero-dimensional-trap
#3
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
https://www.readbyqxmd.com/read/28713845/impact-of-phonons-on-dephasing-of-individual-excitons-in-deterministic-quantum-dot-microlenses
#4
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
https://www.readbyqxmd.com/read/28661144/redfield-treatment-of-multipathway-electron-transfer-in-artificial-photosynthetic-systems
#5
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
https://www.readbyqxmd.com/read/28656726/correlation-distance-dependence-of-the-resonance-frequency-of-intermolecular-zero-quantum-coherences-and-its-implication-for-mr-thermometry
#6
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...
June 27, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28644642/probing-electron-phonon-interaction-through-two-photon-interference-in-resonantly-driven-semiconductor-quantum-dots
#7
Antoine Reigue, Jake Iles-Smith, Fabian Lux, Léonard Monniello, Mathieu Bernard, Florent Margaillan, Aristide Lemaitre, Anthony Martinez, Dara P S McCutcheon, Jesper Mørk, Richard Hostein, Valia Voliotis
We investigate the temperature dependence of photon coherence properties through two-photon interference (TPI) measurements from a single quantum dot (QD) under resonant excitation. We show that the loss of indistinguishability is related only to the electron-phonon coupling and is not affected by spectral diffusion. Through these measurements and a complementary microscopic theory, we identify two independent separate decoherence processes, both of which are associated with phonons. Below 10 K, we find that the relaxation of the vibrational lattice is the dominant contribution to the loss of TPI visibility...
June 9, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28619939/coherent-imaging-of-an-attosecond-electron-wave-packet
#8
D M Villeneuve, Paul Hockett, M J J Vrakking, Hiromichi Niikura
Electrons detached from atoms or molecules by photoionization carry information about the quantum state from which they originate, as well as the continuum states into which they are released. Generally, the photoelectron momentum distribution is composed of a coherent sum of angular momentum components, each with an amplitude and phase. Here we show, by using photoionization of neon, that a train of attosecond pulses synchronized with an infrared laser field can be used to disentangle these angular momentum components...
June 16, 2017: Science
https://www.readbyqxmd.com/read/28560340/inducing-superconductivity-in-weyl-semimetal-microstructures-by-selective-ion-sputtering
#9
Maja D Bachmann, Nityan Nair, Felix Flicker, Roni Ilan, Tobias Meng, Nirmal J Ghimire, Eric D Bauer, Filip Ronning, James G Analytis, Philip J W Moll
By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed...
May 2017: Science Advances
https://www.readbyqxmd.com/read/28522530/high-harmonic-generation-in-graphene-enhanced-by-elliptically-polarized-light-excitation
#10
Naotaka Yoshikawa, Tomohiro Tamaya, Koichiro Tanaka
The electronic properties of graphene can give rise to a range of nonlinear optical responses. One of the most desirable nonlinear optical processes is high-harmonic generation (HHG) originating from coherent electron motion induced by an intense light field. Here, we report on the observation of up to ninth-order harmonics in graphene excited by mid-infrared laser pulses at room temperature. The HHG in graphene is enhanced by an elliptically polarized laser excitation, and the resultant harmonic radiation has a particular polarization...
May 19, 2017: Science
https://www.readbyqxmd.com/read/28401878/negative-and-positive-cross-correlations-of-current-noises-in-quantum-hall-edge-channels-at-bulk-filling-factor-formula-see-text
#11
T Ota, M Hashisaka, K Muraki, T Fujisawa
Cross-correlation noise in electrical currents generated from a series connection of two quantum point contacts (QPCs), the injector and the detector, is described for investigating energy relaxation in quantum Hall edge channels at bulk filling factor [Formula: see text]. We address the importance of tuning the energy bias across the detector for this purpose. For a long channel with a macroscopic floating ohmic contact that thermalizes the electrons, the cross-correlation turns from negative values to the maximally positive value (identical noise in the two currents) by tuning the effective energy bias to zero...
June 7, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28327567/quantum-locality-in-game-strategy
#12
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
https://www.readbyqxmd.com/read/28294106/coherent-and-incoherent-charge-transport-in-linear-triple-quantum-dots
#13
L D Contreras-Pulido, M 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
https://www.readbyqxmd.com/read/28291363/-13-c-decoupled-j-coupling-spectroscopy-using-two-dimensional-nuclear-magnetic-resonance-at-zero-field
#14
Tobias F 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, thus potentially simplifying spectra and thereby improving the analytical capabilities of zero-field NMR...
March 21, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28272546/control-quantum-evolution-speed-of-a-single-dephasing-qubit-for-arbitrary-initial-states-via-periodic-dynamical-decoupling-pulses
#15
Ya-Ju Song, Qing-Shou Tan, Le-Man Kuang
We investigate the possibility to control quantum evolution speed of a single dephasing qubit for arbitrary initial states by the use of periodic dynamical decoupling (PDD) pulses. It is indicated that the quantum speed limit time (QSLT) is determined by initial and final quantum coherence of the qubit, as well as the non-Markovianity of the system under consideration during the evolution when the qubit is subjected to a zero-temperature Ohmic-like dephasing reservoir. It is shown that final quantum coherence of the qubit and the non-Markovianity of the system can be modulated by PDD pulses...
March 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28257610/zero-quantum-coherence-in-a-series-of-covalent-spin-correlated-radical-pairs
#16
Jordan N Nelson, Matthew D Krzyaniak, Noah E Horwitz, Brandon K Rugg, Brian T Phelan, Michael R Wasielewski
Photoinitiated subnanosecond electron transfer within covalently linked electron donor-acceptor molecules can result in the formation of a spin-correlated radical pair (SCRP) with a well-defined initial singlet spin configuration. Subsequent coherent mixing between the SCRP singlet and triplet ms = 0 spin states, the so-called zero quantum coherence (ZQC), is of potential interest in quantum information processing applications because the ZQC can be probed using pulse electron paramagnetic resonance (pulse-EPR) techniques...
March 14, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28134333/discorrelated-quantum-states
#17
Evan Meyer-Scott, Johannes Tiedau, Georg Harder, Lynden K Shalm, Tim J Bartley
The statistical properties of photons are fundamental to investigating quantum mechanical phenomena using light. In multiphoton, two-mode systems, correlations may exist between outcomes of measurements made on each mode which exhibit useful properties. Correlation in this sense can be thought of as increasing the probability of a particular outcome of a measurement on one subsystem given a measurement on a correlated subsystem. Here, we show a statistical property we call "discorrelation", in which the probability of a particular outcome of one subsystem is reduced to zero, given a measurement on a discorrelated subsystem...
January 30, 2017: Scientific Reports
https://www.readbyqxmd.com/read/27982128/microwave-control-of-the-superconducting-proximity-effect-and-minigap-in-magnetic-and-normal-metals
#18
Jacob Linder, Morten Amundsen, Jabir Ali Ouassou
We demonstrate theoretically that microwave radiation applied to superconducting proximity structures controls the minigap and other spectral features in the density of states of normal and magnetic metals, respectively. Considering both a bilayer and Josephson junction geometry, we show that microwaves with frequency ω qualitatively alters the spectral properties of the system: inducing a series of resonances, controlling the minigap size Emg, and even replacing the minigap with a strong peak of quasiparticle accumulation at zero energy when ω = Emg...
December 16, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27892567/high-resolution-two-field-nuclear-magnetic-resonance-spectroscopy
#19
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...
December 7, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27886234/expedited-holonomic-quantum-computation-via-net-zero-energy-cost-control-in-decoherence-free-subspace
#20
P V Pyshkin, Da-Wei Luo, Jun Jing, J Q You, Lian-Ao Wu
Holonomic quantum computation (HQC) may not show its full potential in quantum speedup due to the prerequisite of a long coherent runtime imposed by the adiabatic condition. Here we show that the conventional HQC can be dramatically accelerated by using external control fields, of which the effectiveness is exclusively determined by the integral of the control fields in the time domain. This control scheme can be realized with net zero energy cost and it is fault-tolerant against fluctuation and noise, significantly relaxing the experimental constraints...
November 25, 2016: Scientific Reports
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