Teleportation is necessary for faithful quantum state transfer through noisy channels of maximal rank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romano, Raffaele; Loock, Peter van

2010-07-15

Quantum teleportation enables deterministic and faithful transmission of quantum states, provided a maximally entangled state is preshared between sender and receiver, and a one-way classical channel is available. Here, we prove that these resources are not only sufficient, but also necessary, for deterministically and faithfully sending quantum states through any fixed noisy channel of maximal rank, when a single use of the cannel is admitted. In other words, for this family of channels, there are no other protocols, based on different (and possibly cheaper) sets of resources, capable of replacing quantum teleportation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vignat, C.; Bercher, J.-F.

The family of Tsallis entropies was introduced by Tsallis in 1988. The Shannon entropy belongs to this family as the limit case q{yields}1. The canonical distributions in R{sup n} that maximize this entropy under a covariance constraint are easily derived as Student-t (q<1) and Student-r (q>1) multivariate distributions. A nice geometrical result about these Student-r distributions is that they are marginal of uniform distributions on a sphere of larger dimension d with the relationship p = n+2+(2/q-1). As q{yields}1, we recover the famous Poincare's observation according to which a Gaussian vector can be viewed as the projection of a vectormore » uniformly distributed on the infinite dimensional sphere. A related property in the case q<1 is also available. Often associated to Renyi-Tsallis entropies is the notion of escort distributions. We provide here a geometric interpretation of these distributions. Another result concerns a universal system in physics, the harmonic oscillator: in the usual quantum context, the waveform of the n-th state of the harmonic oscillator is a Gaussian waveform multiplied by the degree n Hermite polynomial. We show, starting from recent results by Carinena et al., that the quantum harmonic oscillator on spaces with constant curvature is described by maximal Tsallis entropy waveforms multiplied by the extended Hermite polynomials derived from this measure. This gives a neat interpretation of the non-extensive parameter q in terms of the curvature of the space the oscillator evolves on; as q{yields}1, the curvature of the space goes to 0 and we recover the classical harmonic oscillator in R{sup 3}.« less

Magneto-transport of an electron bilayer system in an undoped Si/SiGe double-quantum-well heterostructure

DOE PAGES

Laroche, Dominique; Huang, ShiHsien; Nielsen, Erik; ...

2015-04-08

We report the design, the fabrication, and the magneto-transport study of an electron bilayer system embedded in an undoped Si/SiGe double-quantum-well heterostructure. Additionally, the combined Hall densities (n Hall ) ranging from 2.6 × 10 10 cm -2 to 2.7 × 10 11 cm -2 were achieved, yielding a maximal combined Hall mobility (μ Hall ) of 7.7 × 10 5 cm 2/(V • s) at the highest density. Simultaneous electron population of both quantum wells is clearly observed through a Hall mobility drop as the Hall density is increased to n Hall > 3.3 × 10 10 cm -2,more » consistent with Schrödinger-Poisson simulations. Furthermore, the integer and fractional quantum Hall effects are observed in the device, and single-layer behavior is observed when both layers have comparable densities, either due to spontaneous interlayer coherence or to the symmetric-antisymmetric gap.« less

Black hole firewalls require huge energy of measurement

NASA Astrophysics Data System (ADS)

Hotta, Masahiro; Matsumoto, Jiro; Funo, Ken

2014-06-01

The unitary moving mirror model is one of the best quantum systems for checking the reasoning of the original firewall paradox of Almheiri et al. [J. High Energy Phys. 02 (2013) 062] in quantum black holes. Though the late-time part of radiations emitted from the mirror is fully entangled with the early part, no firewall exists with a deadly, huge average energy flux in this model. This is because the high-energy entanglement structure of the discretized systems in almost maximally entangled states is modified so as to yield the correct description of low-energy effective field theory. Furthermore, the strong subadditivity paradox of firewalls is resolved using nonlocality of general one-particle states and zero-point fluctuation entanglement. Due to the Reeh-Schlieder theorem in quantum field theory, another firewall paradox is inevitably raised with quantum remote measurements in the model. We resolve this paradox from the viewpoint of the energy cost of measurements. No firewall appears, as long as the energy for the measurement is much smaller than the ultraviolet cutoff scale.

Versatile Gaussian probes for squeezing estimation

NASA Astrophysics Data System (ADS)

Rigovacca, Luca; Farace, Alessandro; Souza, Leonardo A. M.; De Pasquale, Antonella; Giovannetti, Vittorio; Adesso, Gerardo

2017-05-01

We consider an instance of "black-box" quantum metrology in the Gaussian framework, where we aim to estimate the amount of squeezing applied on an input probe, without previous knowledge on the phase of the applied squeezing. By taking the quantum Fisher information (QFI) as the figure of merit, we evaluate its average and variance with respect to this phase in order to identify probe states that yield good precision for many different squeezing directions. We first consider the case of single-mode Gaussian probes with the same energy, and find that pure squeezed states maximize the average quantum Fisher information (AvQFI) at the cost of a performance that oscillates strongly as the squeezing direction is changed. Although the variance can be brought to zero by correlating the probing system with a reference mode, the maximum AvQFI cannot be increased in the same way. A different scenario opens if one takes into account the effects of photon losses: coherent states represent the optimal single-mode choice when losses exceed a certain threshold and, moreover, correlated probes can now yield larger AvQFI values than all single-mode states, on top of having zero variance.

Growth of Nanosized Single Crystals for Efficient Perovskite Light-Emitting Diodes.

PubMed

Lee, Seungjin; Park, Jong Hyun; Nam, Yun Seok; Lee, Bo Ram; Zhao, Baodan; Di Nuzzo, Daniele; Jung, Eui Dae; Jeon, Hansol; Kim, Ju-Young; Jeong, Hu Young; Friend, Richard H; Song, Myoung Hoon

2018-04-24

Organic-inorganic hybrid perovskites are emerging as promising emitting materials due to their narrow full-width at half-maximum emissions, color tunability, and high photoluminescence quantum yields (PLQYs). However, the thermal generation of free charges at room temperature results in a low radiative recombination rate and an excitation-intensity-dependent PLQY, which is associated with the trap density. Here, we report perovskite films composed of uniform nanosized single crystals (average diameter = 31.7 nm) produced by introducing bulky amine ligands and performing the growth at a lower temperature. By effectively controlling the crystal growth, we maximized the radiative bimolecular recombination yield by reducing the trap density and spatially confining the charges. Finally, highly bright and efficient green emissive perovskite light-emitting diodes that do not suffer from electroluminescence blinking were achieved with a luminance of up to 55 400 cd m -2 , current efficiency of 55.2 cd A -1 , and external quantum efficiency of 12.1%.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lami, L.; Giovannetti, V.

The set of Entanglement Saving (ES) quantum channels is introduced and characterized. These are completely positive, trace preserving transformations which when acting locally on a bipartite quantum system initially prepared into a maximally entangled configuration, preserve its entanglement even when applied an arbitrary number of times. In other words, a quantum channel ψ is said to be ES if its powers ψ{sup n} are not entanglement-breaking for all integers n. We also characterize the properties of the Asymptotic Entanglement Saving (AES) maps. These form a proper subset of the ES channels that is constituted by those maps that not onlymore » preserve entanglement for all finite n but which also sustain an explicitly not null level of entanglement in the asymptotic limit n → ∞. Structure theorems are provided for ES and for AES maps which yield an almost complete characterization of the former and a full characterization of the latter.« less

Quantum coherence generating power, maximally abelian subalgebras, and Grassmannian geometry

NASA Astrophysics Data System (ADS)

Zanardi, Paolo; Campos Venuti, Lorenzo

2018-01-01

We establish a direct connection between the power of a unitary map in d-dimensions (d < ∞) to generate quantum coherence and the geometry of the set Md of maximally abelian subalgebras (of the quantum system full operator algebra). This set can be seen as a topologically non-trivial subset of the Grassmannian over linear operators. The natural distance over the Grassmannian induces a metric structure on Md, which quantifies the lack of commutativity between the pairs of subalgebras. Given a maximally abelian subalgebra, one can define, on physical grounds, an associated measure of quantum coherence. We show that the average quantum coherence generated by a unitary map acting on a uniform ensemble of quantum states in the algebra (the so-called coherence generating power of the map) is proportional to the distance between a pair of maximally abelian subalgebras in Md connected by the unitary transformation itself. By embedding the Grassmannian into a projective space, one can pull-back the standard Fubini-Study metric on Md and define in this way novel geometrical measures of quantum coherence generating power. We also briefly discuss the associated differential metric structures.

Quantum-Inspired Maximizer

NASA Technical Reports Server (NTRS)

Zak, Michail

2008-01-01

A report discusses an algorithm for a new kind of dynamics based on a quantum- classical hybrid-quantum-inspired maximizer. The model is represented by a modified Madelung equation in which the quantum potential is replaced by different, specially chosen 'computational' potential. As a result, the dynamics attains both quantum and classical properties: it preserves superposition and entanglement of random solutions, while allowing one to measure its state variables, using classical methods. Such optimal combination of characteristics is a perfect match for quantum-inspired computing. As an application, an algorithm for global maximum of an arbitrary integrable function is proposed. The idea of the proposed algorithm is very simple: based upon the Quantum-inspired Maximizer (QIM), introduce a positive function to be maximized as the probability density to which the solution is attracted. Then the larger value of this function will have the higher probability to appear. Special attention is paid to simulation of integer programming and NP-complete problems. It is demonstrated that the problem of global maximum of an integrable function can be found in polynomial time by using the proposed quantum- classical hybrid. The result is extended to a constrained maximum with applications to integer programming and TSP (Traveling Salesman Problem).

Projection of two biphoton qutrits onto a maximally entangled state.

PubMed

Halevy, A; Megidish, E; Shacham, T; Dovrat, L; Eisenberg, H S

2011-04-01

Bell state measurements, in which two quantum bits are projected onto a maximally entangled state, are an essential component of quantum information science. We propose and experimentally demonstrate the projection of two quantum systems with three states (qutrits) onto a generalized maximally entangled state. Each qutrit is represented by the polarization of a pair of indistinguishable photons-a biphoton. The projection is a joint measurement on both biphotons using standard linear optics elements. This demonstration enables the realization of quantum information protocols with qutrits, such as teleportation and entanglement swapping. © 2011 American Physical Society

Deterministic generation of remote entanglement with active quantum feedback

DOE PAGES

Martin, Leigh; Motzoi, Felix; Li, Hanhan; ...

2015-12-10

We develop and study protocols for deterministic remote entanglement generation using quantum feedback, without relying on an entangling Hamiltonian. In order to formulate the most effective experimentally feasible protocol, we introduce the notion of average-sense locally optimal feedback protocols, which do not require real-time quantum state estimation, a difficult component of real-time quantum feedback control. We use this notion of optimality to construct two protocols that can deterministically create maximal entanglement: a semiclassical feedback protocol for low-efficiency measurements and a quantum feedback protocol for high-efficiency measurements. The latter reduces to direct feedback in the continuous-time limit, whose dynamics can bemore » modeled by a Wiseman-Milburn feedback master equation, which yields an analytic solution in the limit of unit measurement efficiency. Our formalism can smoothly interpolate between continuous-time and discrete-time descriptions of feedback dynamics and we exploit this feature to derive a superior hybrid protocol for arbitrary nonunit measurement efficiency that switches between quantum and semiclassical protocols. Lastly, we show using simulations incorporating experimental imperfections that deterministic entanglement of remote superconducting qubits may be achieved with current technology using the continuous-time feedback protocol alone.« less

Quantum speedup in solving the maximal-clique problem

NASA Astrophysics Data System (ADS)

Chang, Weng-Long; Yu, Qi; Li, Zhaokai; Chen, Jiahui; Peng, Xinhua; Feng, Mang

2018-03-01

The maximal-clique problem, to find the maximally sized clique in a given graph, is classically an NP-complete computational problem, which has potential applications ranging from electrical engineering, computational chemistry, and bioinformatics to social networks. Here we develop a quantum algorithm to solve the maximal-clique problem for any graph G with n vertices with quadratic speedup over its classical counterparts, where the time and spatial complexities are reduced to, respectively, O (√{2n}) and O (n2) . With respect to oracle-related quantum algorithms for the NP-complete problems, we identify our algorithm as optimal. To justify the feasibility of the proposed quantum algorithm, we successfully solve a typical clique problem for a graph G with two vertices and one edge by carrying out a nuclear magnetic resonance experiment involving four qubits.

One-Shot Coherence Dilution.

PubMed

Zhao, Qi; Liu, Yunchao; Yuan, Xiao; Chitambar, Eric; Ma, Xiongfeng

2018-02-16

Manipulation and quantification of quantum resources are fundamental problems in quantum physics. In the asymptotic limit, coherence distillation and dilution have been proposed by manipulating infinite identical copies of states. In the nonasymptotic setting, finite data-size effects emerge, and the practically relevant problem of coherence manipulation using finite resources has been left open. This Letter establishes the one-shot theory of coherence dilution, which involves converting maximally coherent states into an arbitrary quantum state using maximally incoherent operations, dephasing-covariant incoherent operations, incoherent operations, or strictly incoherent operations. We introduce several coherence monotones with concrete operational interpretations that estimate the one-shot coherence cost-the minimum amount of maximally coherent states needed for faithful coherence dilution. Furthermore, we derive the asymptotic coherence dilution results with maximally incoherent operations, incoherent operations, and strictly incoherent operations as special cases. Our result can be applied in the analyses of quantum information processing tasks that exploit coherence as resources, such as quantum key distribution and random number generation.

One-Shot Coherence Dilution

NASA Astrophysics Data System (ADS)

Zhao, Qi; Liu, Yunchao; Yuan, Xiao; Chitambar, Eric; Ma, Xiongfeng

2018-02-01

Manipulation and quantification of quantum resources are fundamental problems in quantum physics. In the asymptotic limit, coherence distillation and dilution have been proposed by manipulating infinite identical copies of states. In the nonasymptotic setting, finite data-size effects emerge, and the practically relevant problem of coherence manipulation using finite resources has been left open. This Letter establishes the one-shot theory of coherence dilution, which involves converting maximally coherent states into an arbitrary quantum state using maximally incoherent operations, dephasing-covariant incoherent operations, incoherent operations, or strictly incoherent operations. We introduce several coherence monotones with concrete operational interpretations that estimate the one-shot coherence cost—the minimum amount of maximally coherent states needed for faithful coherence dilution. Furthermore, we derive the asymptotic coherence dilution results with maximally incoherent operations, incoherent operations, and strictly incoherent operations as special cases. Our result can be applied in the analyses of quantum information processing tasks that exploit coherence as resources, such as quantum key distribution and random number generation.

One-way quantum computing in superconducting circuits

NASA Astrophysics Data System (ADS)

Albarrán-Arriagada, F.; Alvarado Barrios, G.; Sanz, M.; Romero, G.; Lamata, L.; Retamal, J. C.; Solano, E.

2018-03-01

We propose a method for the implementation of one-way quantum computing in superconducting circuits. Measurement-based quantum computing is a universal quantum computation paradigm in which an initial cluster state provides the quantum resource, while the iteration of sequential measurements and local rotations encodes the quantum algorithm. Up to now, technical constraints have limited a scalable approach to this quantum computing alternative. The initial cluster state can be generated with available controlled-phase gates, while the quantum algorithm makes use of high-fidelity readout and coherent feedforward. With current technology, we estimate that quantum algorithms with above 20 qubits may be implemented in the path toward quantum supremacy. Moreover, we propose an alternative initial state with properties of maximal persistence and maximal connectedness, reducing the required resources of one-way quantum computing protocols.

Deterministic quantum annealing expectation-maximization algorithm

NASA Astrophysics Data System (ADS)

Miyahara, Hideyuki; Tsumura, Koji; Sughiyama, Yuki

2017-11-01

Maximum likelihood estimation (MLE) is one of the most important methods in machine learning, and the expectation-maximization (EM) algorithm is often used to obtain maximum likelihood estimates. However, EM heavily depends on initial configurations and fails to find the global optimum. On the other hand, in the field of physics, quantum annealing (QA) was proposed as a novel optimization approach. Motivated by QA, we propose a quantum annealing extension of EM, which we call the deterministic quantum annealing expectation-maximization (DQAEM) algorithm. We also discuss its advantage in terms of the path integral formulation. Furthermore, by employing numerical simulations, we illustrate how DQAEM works in MLE and show that DQAEM moderate the problem of local optima in EM.

Braid group representation on quantum computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aziz, Ryan Kasyfil, E-mail: kasyfilryan@gmail.com; Muchtadi-Alamsyah, Intan, E-mail: ntan@math.itb.ac.id

2015-09-30

There are many studies about topological representation of quantum computation recently. One of diagram representation of quantum computation is by using ZX-Calculus. In this paper we will make a diagrammatical scheme of Dense Coding. We also proved that ZX-Calculus diagram of maximally entangle state satisfies Yang-Baxter Equation and therefore, we can construct a Braid Group representation of set of maximally entangle state.

Operational quantification of continuous-variable correlations.

PubMed

Rodó, Carles; Adesso, Gerardo; Sanpera, Anna

2008-03-21

We quantify correlations (quantum and/or classical) between two continuous-variable modes as the maximal number of correlated bits extracted via local quadrature measurements. On Gaussian states, such "bit quadrature correlations" majorize entanglement, reducing to an entanglement monotone for pure states. For non-Gaussian states, such as photonic Bell states, photon-subtracted states, and mixtures of Gaussian states, the bit correlations are shown to be a monotonic function of the negativity. This quantification yields a feasible, operational way to measure non-Gaussian entanglement in current experiments by means of direct homodyne detection, without a complete state tomography.

Tight upper bound for the maximal quantum value of the Svetlichny operators

NASA Astrophysics Data System (ADS)

Li, Ming; Shen, Shuqian; Jing, Naihuan; Fei, Shao-Ming; Li-Jost, Xianqing

2017-10-01

It is a challenging task to detect genuine multipartite nonlocality (GMNL). In this paper, the problem is considered via computing the maximal quantum value of Svetlichny operators for three-qubit systems and a tight upper bound is obtained. The constraints on the quantum states for the tightness of the bound are also presented. The approach enables us to give the necessary and sufficient conditions of violating the Svetlichny inequality (SI) for several quantum states, including the white and color noised Greenberger-Horne-Zeilinger (GHZ) states. The relation between the genuine multipartite entanglement concurrence and the maximal quantum value of the Svetlichny operators for mixed GHZ class states is also discussed. As the SI is useful for the investigation of GMNL, our results give an effective and operational method to detect the GMNL for three-qubit mixed states.

Linear maps preserving maximal deviation and the Jordan structure of quantum systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamhalter, Jan

2012-12-15

In the algebraic approach to quantum theory, a quantum observable is given by an element of a Jordan algebra and a state of the system is modelled by a normalized positive functional on the underlying algebra. Maximal deviation of a quantum observable is the largest statistical deviation one can obtain in a particular state of the system. The main result of the paper shows that each linear bijective transformation between JBW algebras preserving maximal deviations is formed by a Jordan isomorphism or a minus Jordan isomorphism perturbed by a linear functional multiple of an identity. It shows that only onemore » numerical statistical characteristic has the power to determine the Jordan algebraic structure completely. As a consequence, we obtain that only very special maps can preserve the diameter of the spectra of elements. Nonlinear maps preserving the pseudometric given by maximal deviation are also described. The results generalize hitherto known theorems on preservers of maximal deviation in the case of self-adjoint parts of von Neumann algebras proved by Molnar.« less

Quasideterministic generation of maximally entangled states of two mesoscopic atomic ensembles by adiabatic quantum feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Lisi, Antonio; De Siena, Silvio; Illuminati, Fabrizio

2005-09-15

We introduce an efficient, quasideterministic scheme to generate maximally entangled states of two atomic ensembles. The scheme is based on quantum nondemolition measurements of total atomic populations and on adiabatic quantum feedback conditioned by the measurements outputs. The high efficiency of the scheme is tested and confirmed numerically for ideal photodetection as well as in the presence of losses.

Base norms and discrimination of generalized quantum channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jenčová, A.

2014-02-15

We introduce and study norms in the space of hermitian matrices, obtained from base norms in positively generated subspaces. These norms are closely related to discrimination of so-called generalized quantum channels, including quantum states, channels, and networks. We further introduce generalized quantum decision problems and show that the maximal average payoffs of decision procedures are again given by these norms. We also study optimality of decision procedures, in particular, we obtain a necessary and sufficient condition under which an optimal 1-tester for discrimination of quantum channels exists, such that the input state is maximally entangled.

Minimal universal quantum heat machine.

PubMed

Gelbwaser-Klimovsky, D; Alicki, R; Kurizki, G

2013-01-01

In traditional thermodynamics the Carnot cycle yields the ideal performance bound of heat engines and refrigerators. We propose and analyze a minimal model of a heat machine that can play a similar role in quantum regimes. The minimal model consists of a single two-level system with periodically modulated energy splitting that is permanently, weakly, coupled to two spectrally separated heat baths at different temperatures. The equation of motion allows us to compute the stationary power and heat currents in the machine consistent with the second law of thermodynamics. This dual-purpose machine can act as either an engine or a refrigerator (heat pump) depending on the modulation rate. In both modes of operation, the maximal Carnot efficiency is reached at zero power. We study the conditions for finite-time optimal performance for several variants of the model. Possible realizations of the model are discussed.

Quantum teleportation via quantum channels with non-maximal Schmidt rank

NASA Astrophysics Data System (ADS)

Solís-Prosser, M. A.; Jiménez, O.; Neves, L.; Delgado, A.

2013-03-01

We study the problem of teleporting unknown pure states of a single qudit via a pure quantum channel with non-maximal Schmidt rank. We relate this process to the discrimination of linearly dependent symmetric states with the help of the maximum-confidence discrimination strategy. We show that with a certain probability, it is possible to teleport with a fidelity larger than the fidelity optimal deterministic teleportation.

Exploring constrained quantum control landscapes

NASA Astrophysics Data System (ADS)

Moore, Katharine W.; Rabitz, Herschel

2012-10-01

The broad success of optimally controlling quantum systems with external fields has been attributed to the favorable topology of the underlying control landscape, where the landscape is the physical observable as a function of the controls. The control landscape can be shown to contain no suboptimal trapping extrema upon satisfaction of reasonable physical assumptions, but this topological analysis does not hold when significant constraints are placed on the control resources. This work employs simulations to explore the topology and features of the control landscape for pure-state population transfer with a constrained class of control fields. The fields are parameterized in terms of a set of uniformly spaced spectral frequencies, with the associated phases acting as the controls. This restricted family of fields provides a simple illustration for assessing the impact of constraints upon seeking optimal control. Optimization results reveal that the minimum number of phase controls necessary to assure a high yield in the target state has a special dependence on the number of accessible energy levels in the quantum system, revealed from an analysis of the first- and second-order variation of the yield with respect to the controls. When an insufficient number of controls and/or a weak control fluence are employed, trapping extrema and saddle points are observed on the landscape. When the control resources are sufficiently flexible, solutions producing the globally maximal yield are found to form connected "level sets" of continuously variable control fields that preserve the yield. These optimal yield level sets are found to shrink to isolated points on the top of the landscape as the control field fluence is decreased, and further reduction of the fluence turns these points into suboptimal trapping extrema on the landscape. Although constrained control fields can come in many forms beyond the cases explored here, the behavior found in this paper is illustrative of the impacts that constraints can introduce.

SU-E-T-191: First Principle Calculation of Quantum Yield in Photodynamic Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abolfath, R; Guo, F; Chen, Z

Purpose: We present a first-principle method to calculate the spin transfer efficiency in oxygen induced by any photon fields especially in MeV energy range. The optical pumping is mediated through photosensitizers, e.g., porphyrin and/or ensemble of quantum dots. Methods: Under normal conditions, oxygen molecules are in the relatively non-reactive triplet state. In the presence of certain photosensitizer compounds such as porphyrins, electromagnetic radiation of specific wavelengths can excite oxygen to highly reactive singlet state. With selective uptake of photosensitizers by certain malignant cells, photon irradiation of phosensitized tumors can lead to selective killing of cancer cells. This is the basismore » of photodynamic therapy (PDT). Despite several attempts, PDT has not been clinically successful except in limited superficial cancers. Many parameters such as photon energy, conjugation with quantum dots etc. can be potentially combined with PDT in order to extend the role of PDT in cancer management. The key quantity for this optimization is the spin transfer efficiency in oxygen by any photon field. The first principle calculation model presented here, is an attempt to fill this need. We employ stochastic density matrix description of the quantum jumps and the rate equation methods in quantum optics based on Markov/Poisson processes and calculate time evolution of the population of the optically pumped singlet oxygen. Results: The results demonstrate the feasibility of our model in showing the dependence of the optical yield in generating spin-singlet oxygen on the experimental conditions. The adjustable variables can be tuned to maximize the population of the singlet oxygen hence the efficacy of the photodynamic therapy. Conclusion: The present model can be employed to fit and analyze the experimental data and possibly to assist researchers in optimizing the experimental conditions in photodynamic therapy.« less

Analysis of entanglement measures and LOCC maximized quantum Fisher information of general two qubit systems.

PubMed

Erol, Volkan; Ozaydin, Fatih; Altintas, Azmi Ali

2014-06-24

Entanglement has been studied extensively for unveiling the mysteries of non-classical correlations between quantum systems. In the bipartite case, there are well known measures for quantifying entanglement such as concurrence, relative entropy of entanglement (REE) and negativity, which cannot be increased via local operations. It was found that for sets of non-maximally entangled states of two qubits, comparing these entanglement measures may lead to different entanglement orderings of the states. On the other hand, although it is not an entanglement measure and not monotonic under local operations, due to its ability of detecting multipartite entanglement, quantum Fisher information (QFI) has recently received an intense attraction generally with entanglement in the focus. In this work, we revisit the state ordering problem of general two qubit states. Generating a thousand random quantum states and performing an optimization based on local general rotations of each qubit, we calculate the maximal QFI for each state. We analyze the maximized QFI in comparison with concurrence, REE and negativity and obtain new state orderings. We show that there are pairs of states having equal maximized QFI but different values for concurrence, REE and negativity and vice versa.

Analysis of Entanglement Measures and LOCC Maximized Quantum Fisher Information of General Two Qubit Systems

PubMed Central

Erol, Volkan; Ozaydin, Fatih; Altintas, Azmi Ali

2014-01-01

Entanglement has been studied extensively for unveiling the mysteries of non-classical correlations between quantum systems. In the bipartite case, there are well known measures for quantifying entanglement such as concurrence, relative entropy of entanglement (REE) and negativity, which cannot be increased via local operations. It was found that for sets of non-maximally entangled states of two qubits, comparing these entanglement measures may lead to different entanglement orderings of the states. On the other hand, although it is not an entanglement measure and not monotonic under local operations, due to its ability of detecting multipartite entanglement, quantum Fisher information (QFI) has recently received an intense attraction generally with entanglement in the focus. In this work, we revisit the state ordering problem of general two qubit states. Generating a thousand random quantum states and performing an optimization based on local general rotations of each qubit, we calculate the maximal QFI for each state. We analyze the maximized QFI in comparison with concurrence, REE and negativity and obtain new state orderings. We show that there are pairs of states having equal maximized QFI but different values for concurrence, REE and negativity and vice versa. PMID:24957694

Mathematical problems of quantum teleportation

NASA Astrophysics Data System (ADS)

Tanaka, Yoshiharu; Asano, Masanari; Ohya, Masanori

2011-03-01

It has been considered that a maximal entangled state is needed for complete quantum teleportation. However, Kossakowski and Ohya proposed a scheme of complete teleportation for nonmaximal entangled state [1]. Basing on their scheme, we proposed a teleportation model of 2-level state with a non-maximal entangled state [2]. In the present study, we construct its expanded model, in which Alice can teleport m-level state even if non-maximal entangled state is used.

Quantum correlations of two-qubit states with one maximally mixed marginal

NASA Astrophysics Data System (ADS)

Milne, Antony; Jennings, David; Jevtic, Sania; Rudolph, Terry

2014-08-01

We investigate the entanglement, CHSH nonlocality, fully entangled fraction, and symmetric extendibility of two-qubit states that have a single maximally mixed marginal. Within this set of states, the steering ellipsoid formalism has recently highlighted an interesting family of so-called maximally obese states. These are found to have extremal quantum correlation properties that are significant in the steering ellipsoid picture and for the study of two-qubit states in general.

Entanglement Entropy of Eigenstates of Quantum Chaotic Hamiltonians.

PubMed

Vidmar, Lev; Rigol, Marcos

2017-12-01

In quantum statistical mechanics, it is of fundamental interest to understand how close the bipartite entanglement entropy of eigenstates of quantum chaotic Hamiltonians is to maximal. For random pure states in the Hilbert space, the average entanglement entropy is known to be nearly maximal, with a deviation that is, at most, a constant. Here we prove that, in a system that is away from half filling and divided in two equal halves, an upper bound for the average entanglement entropy of random pure states with a fixed particle number and normally distributed real coefficients exhibits a deviation from the maximal value that grows with the square root of the volume of the system. Exact numerical results for highly excited eigenstates of a particle number conserving quantum chaotic model indicate that the bound is saturated with increasing system size.

Continuous-variable quantum teleportation with non-Gaussian resources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dell'Anno, F.; Dipartimento di Fisica, Universita degli Studi di Salerno, Via S. Allende, I-84081 Baronissi; CNR-INFM Coherentia, Napoli, Italy and CNISM Unita di Salerno and INFN Sezione di Napoli, Gruppo Collegato di Salerno, Baronissi

2007-08-15

We investigate continuous variable quantum teleportation using non-Gaussian states of the radiation field as entangled resources. We compare the performance of different classes of degaussified resources, including two-mode photon-added and two-mode photon-subtracted squeezed states. We then introduce a class of two-mode squeezed Bell-like states with one-parameter dependence for optimization. These states interpolate between and include as subcases different classes of degaussified resources. We show that optimized squeezed Bell-like resources yield a remarkable improvement in the fidelity of teleportation both for coherent and nonclassical input states. The investigation reveals that the optimal non-Gaussian resources for continuous variable teleportation are those thatmore » most closely realize the simultaneous maximization of the content of entanglement, the degree of affinity with the two-mode squeezed vacuum, and the, suitably measured, amount of non-Gaussianity.« less

Flexible White Light Emitting Diodes Based on Nitride Nanowires and Nanophosphors

PubMed Central

2016-01-01

We report the first demonstration of flexible white phosphor-converted light emitting diodes (LEDs) based on p–n junction core/shell nitride nanowires. GaN nanowires containing seven radial In0.2Ga0.8N/GaN quantum wells were grown by metal–organic chemical vapor deposition on a sapphire substrate by a catalyst-free approach. To fabricate the flexible LED, the nanowires are embedded into a phosphor-doped polymer matrix, peeled off from the growth substrate, and contacted using a flexible and transparent silver nanowire mesh. The electroluminescence of a flexible device presents a cool-white color with a spectral distribution covering a broad spectral range from 400 to 700 nm. Mechanical bending stress down to a curvature radius of 5 mm does not yield any degradation of the LED performance. The maximal measured external quantum efficiency of the white LED is 9.3%, and the wall plug efficiency is 2.4%. PMID:27331079

Current fluctuations in quantum absorption refrigerators

NASA Astrophysics Data System (ADS)

Segal, Dvira

2018-05-01

Absorption refrigerators transfer thermal energy from a cold bath to a hot bath without input power by utilizing heat from an additional "work" reservoir. Particularly interesting is a three-level design for a quantum absorption refrigerator, which can be optimized to reach the maximal (Carnot) cooling efficiency. Previous studies of three-level chillers focused on the behavior of the averaged cooling current. Here, we go beyond that and study the full counting statistics of heat exchange in a three-level chiller model. We explain how to obtain the complete cumulant generating function of the refrigerator in a steady state, then derive a partial cumulant generating function, which yields closed-form expressions for both the averaged cooling current and its noise. Our analytical results and simulations are beneficial for the design of nanoscale engines and cooling systems far from equilibrium, with their performance optimized according to different criteria, efficiency, power, fluctuations, and dissipation.

Ultimate Data Hiding in Quantum Mechanics and Beyond

NASA Astrophysics Data System (ADS)

Lami, Ludovico; Palazuelos, Carlos; Winter, Andreas

2018-06-01

The phenomenon of data hiding, i.e. the existence of pairs of states of a bipartite system that are perfectly distinguishable via general entangled measurements yet almost indistinguishable under LOCC, is a distinctive signature of nonclassicality. The relevant figure of merit is the maximal ratio (called data hiding ratio) between the distinguishability norms associated with the two sets of measurements we are comparing, typically all measurements vs LOCC protocols. For a bipartite {n× n} quantum system, it is known that the data hiding ratio scales as n, i.e. the square root of the real dimension of the local state space of density matrices. We show that for bipartite {n_A× n_B} systems the maximum data hiding ratio against LOCC protocols is Θ(\\min{n_A,n_B}) . This scaling is better than the previously obtained upper bounds O(√{n_A n_B}) and \\min{n_A^2, n_B^2} , and moreover our intuitive argument yields constants close to optimal. In this paper, we investigate data hiding in the more general context of general probabilistic theories (GPTs), an axiomatic framework for physical theories encompassing only the most basic requirements about the predictive power of the theory. The main result of the paper is the determination of the maximal data hiding ratio obtainable in an arbitrary GPT, which is shown to scale linearly in the minimum of the local dimensions. We exhibit an explicit model achieving this bound up to additive constants, finding that quantum mechanical data hiding ratio is only of the order of the square root of the maximal one. Our proof rests crucially on an unexpected link between data hiding and the theory of projective and injective tensor products of Banach spaces. Finally, we develop a body of techniques to compute data hiding ratios for a variety of restricted classes of GPTs that support further symmetries.

Combined low temperature-high light effects on gas exchange properties of jojoba leaves.

PubMed

Loreto, F; Bongi, G

1989-12-01

Jojoba (Simmondsia chinensis [Link] Schneider) is an important crop in desert climates. A relatively high frequency of periods of chilling and high photon flux density (PFD) in this environment makes photoinhibition likely, resulting in a reduction of assimilation capacity in overwintering leaves. This could explain the low net photosynthesis found in shoots from the field (4-6 micromoles per square meter per second) when compared to greenhouse grown plants (12-15 micromoles per square meter per second). The responses of photosynthesis and stomatal conductance to changes in absorbed PFD and in substomatal partial pressure of CO(2) were measured on jojoba leaves recovering from chilling temperature (4 degrees C) in high or low PFD. No measurable gas exchange was found immediately after chilling in either high or low PFD. For leaves chilled in low PFD, the original quantum yield was restored after 24 hours. The time course of recovery from chilling in high PFD was much longer. Quantum yield recovered to 60% of its original value in 72 hours but failed to recover fully after 1 week. Measurements of PSII chlorophyll fluorescence at 77 K showed that the reduced quantum yield was caused by photoinhibition. The ratio of variable to maximal fluorescence fell from a control level of 0.82 to 0.41 after the photoinhibitory treatment and recovery was slow. We also found a large increase in net assimilation rate and little closure of stomata as CO(2) was increased from ambient partial pressure of 35 to 85 pascals. For plants grown in full light, the increase in net assimilation rate was 100%. The photosynthetic response at high CO(2) concentration may constitute an ecological advantage of jojoba as a crop in the future.

Combined Low Temperature-High Light Effects on Gas Exchange Properties of Jojoba Leaves 1

PubMed Central

Loreto, Francesco; Bongi, Guido

1989-01-01

Jojoba (Simmondsia chinensis [Link] Schneider) is an important crop in desert climates. A relatively high frequency of periods of chilling and high photon flux density (PFD) in this environment makes photoinhibition likely, resulting in a reduction of assimilation capacity in overwintering leaves. This could explain the low net photosynthesis found in shoots from the field (4-6 micromoles per square meter per second) when compared to greenhouse grown plants (12-15 micromoles per square meter per second). The responses of photosynthesis and stomatal conductance to changes in absorbed PFD and in substomatal partial pressure of CO2 were measured on jojoba leaves recovering from chilling temperature (4°C) in high or low PFD. No measurable gas exchange was found immediately after chilling in either high or low PFD. For leaves chilled in low PFD, the original quantum yield was restored after 24 hours. The time course of recovery from chilling in high PFD was much longer. Quantum yield recovered to 60% of its original value in 72 hours but failed to recover fully after 1 week. Measurements of PSII chlorophyll fluorescence at 77 K showed that the reduced quantum yield was caused by photoinhibition. The ratio of variable to maximal fluorescence fell from a control level of 0.82 to 0.41 after the photoinhibitory treatment and recovery was slow. We also found a large increase in net assimilation rate and little closure of stomata as CO2 was increased from ambient partial pressure of 35 to 85 pascals. For plants grown in full light, the increase in net assimilation rate was 100%. The photosynthetic response at high CO2 concentration may constitute an ecological advantage of jojoba as a crop in the future. PMID:16667220

The Effect of Copper and Selenium Nanocarboxylates on Biomass Accumulation and Photosynthetic Energy Transduction Efficiency of the Green Algae Chlorella Vulgaris

NASA Astrophysics Data System (ADS)

Mykhaylenko, Natalia F.; Zolotareva, Elena K.

2017-02-01

Nanoaquachelates, the nanoparticles with the molecules of water and/or carboxylic acids as ligands, are used in many fields of biotechnology. Ultra-pure nanocarboxylates of microelements are the materials of spatial perspective. In the present work, the effects of copper and selenium nanoaquachelates carboxylated with citric acid on biomass accumulation of the green algae Chlorella vulgaris were examined. Besides, the efficiency of the reactions of the light stage of photosynthesis was estimated by measuring chlorophyll a fluorescence. The addition of 0.67-4 mg L-1 of Cu nanocarboxylates resulted in the increase in Chlorella biomass by ca. 20%; however, their concentrations ranging from 20 to 40 mg L-1 strongly inhibited algal growth after the 12th day of cultivation. Se nanocarboxylates at 0.4-4 mg L-1 concentrations also stimulated the growth of C. vulgaris, and the increase in biomass came up to 40-45%. The addition of Se nanocarboxylates at smaller concentrations (0.07 or 0.2 mg L-1) at first caused the retardation of culture growth, but that effect disappeared after 18-24 days of cultivation. The addition of 2-4 mg L-1 of Cu nanocarboxylates or 0.4-4 mg L-1 of Se nanocarboxylates caused the evident initial increase in such chlorophyll a fluorescence parameters as maximal quantum yield of photosystem II photochemistry ( F v/ F m) and the quantum yield of photosystem II photochemistry in the light-adapted state ( F v'/ F m'). Photochemical fluorescence quenching coefficients declined after 24 days of growth with Cu nanocarboxylates, but they increased after 6 days of the addition of 2 or 4 mg L-1 Se nanocarboxylates. Those alterations affected the overall quantum yield of the photosynthetic electron transport in photosystem II.

Maximal coherence and the resource theory of purity

NASA Astrophysics Data System (ADS)

Streltsov, Alexander; Kampermann, Hermann; Wölk, Sabine; Gessner, Manuel; Bruß, Dagmar

2018-05-01

The resource theory of quantum coherence studies the off-diagonal elements of a density matrix in a distinguished basis, whereas the resource theory of purity studies all deviations from the maximally mixed state. We establish a direct connection between the two resource theories, by identifying purity as the maximal coherence which is achievable by unitary operations. The states that saturate this maximum identify a universal family of maximally coherent mixed states. These states are optimal resources under maximally incoherent operations, and thus independent of the way coherence is quantified. For all distance-based coherence quantifiers the maximal coherence can be evaluated exactly, and is shown to coincide with the corresponding distance-based purity quantifier. We further show that purity bounds the maximal amount of entanglement and discord that can be generated by unitary operations, thus demonstrating that purity is the most elementary resource for quantum information processing.

Probing structure and dynamics of DNA with 2-aminopurine: effects of local environment on fluorescence.

PubMed

Rachofsky, E L; Osman, R; Ross, J B

2001-01-30

2-Aminopurine (2AP) is an analogue of adenine that has been utilized widely as a fluorescence probe of protein-induced local conformational changes in DNA. Within a DNA strand, this fluorophore demonstrates characteristic decreases in quantum yield and emission decay lifetime that vary sensitively with base sequence, temperature, and helix conformation but that are accompanied by only small changes in emission wavelength. However, the molecular interactions that give rise to these spectroscopic changes have not been established. To develop a molecular model for interpreting the fluorescence measurements, we have investigated the effects of environmental polarity, hydrogen bonding, and the purine and pyrimidine bases of DNA on the emission energy, quantum yield, and intensity decay kinetics of 2AP in simple model systems. The effects of environmental polarity were examined in a series of solvents of varying dielectric constant, and hydrogen bonding was investigated in binary mixtures of water with 1,4-dioxane or N,N-dimethylformamide (DMF). The effects of the purine and pyrimidine bases were studied by titrating 2AP deoxyriboside (d2AP) with the nucleosides adenosine (rA), cytidine (rC), guanosine (rG), and deoxythymidine (dT), and the nucleoside triphosphates ATP and GTP in neutral aqueous solution. The nucleosides and NTPs each quench the fluorescence of d2AP by a combination of static (affecting only the quantum yield) and dynamic (affecting both the quantum yield and the lifetime, proportionately) mechanisms. The peak wavelength and shape of the emission spectrum are not altered by either of these effects. The static quenching is saturable and has half-maximal effect at approximately 20 mM nucleoside or NTP, consistent with an aromatic stacking interaction. The rate constant for dynamic quenching is near the diffusion limit for collisional interaction (k(q) approximately 2 x 10(9) M(-1) s(-1)). Neither of these effects varies significantly between the various nucleosides and NTPs studied. In contrast, hydrogen bonding with water was observed to have a negligible effect on the emission wavelength, fluorescence quantum yield, or lifetime of 2AP in either dioxane or DMF. In nonpolar solvents, the fluorescence lifetime and quantum yield decrease dramatically, accompanied by significant shifts in the emission spectrum to shorter wavelengths. However, these effects of polarity do not coincide with the observed emission wavelength-independent quenching of 2AP fluorescence in DNA. Therefore, we conclude that the fluorescence quenching of 2AP in DNA arises from base stacking and collisions with neighboring bases only but is insensitive to base-pairing or other hydrogen bonding interactions. These results implicate both structural and dynamic properties of DNA in quenching of 2AP and constitute a simple model within which the fluorescence changes induced by protein-DNA binding or other perturbations may be interpreted.

Quantum Tasks with Non-maximally Quantum Channels via Positive Operator-Valued Measurement

NASA Astrophysics Data System (ADS)

Peng, Jia-Yin; Luo, Ming-Xing; Mo, Zhi-Wen

2013-01-01

By using a proper positive operator-valued measure (POVM), we present two new schemes for probabilistic transmission with non-maximally four-particle cluster states. In the first scheme, we demonstrate that two non-maximally four-particle cluster states can be used to realize probabilistically sharing an unknown three-particle GHZ-type state within either distant agent's place. In the second protocol, we demonstrate that a non-maximally four-particle cluster state can be used to teleport an arbitrary unknown multi-particle state in a probabilistic manner with appropriate unitary operations and POVM. Moreover the total success probability of these two schemes are also worked out.

Optimal quantum error correcting codes from absolutely maximally entangled states

NASA Astrophysics Data System (ADS)

Raissi, Zahra; Gogolin, Christian; Riera, Arnau; Acín, Antonio

2018-02-01

Absolutely maximally entangled (AME) states are pure multi-partite generalizations of the bipartite maximally entangled states with the property that all reduced states of at most half the system size are in the maximally mixed state. AME states are of interest for multipartite teleportation and quantum secret sharing and have recently found new applications in the context of high-energy physics in toy models realizing the AdS/CFT-correspondence. We work out in detail the connection between AME states of minimal support and classical maximum distance separable (MDS) error correcting codes and, in particular, provide explicit closed form expressions for AME states of n parties with local dimension \

The dissociative recombination of O2(+) - The quantum yield of O(1S) and O(1D)

NASA Technical Reports Server (NTRS)

Abreu, V. J.; Solomon, S. C.; Sharp, W. E.; Hays, P. B.

1983-01-01

Data from the visible airglow experiment on the Atmosphere Explorer-E satellite have been used to determine the quantum yield of O(1S) and O(1D) from the dissociative recombination of O2(+). A range of values between 0.09 and 0.23 has been obtained for the quantum yield of O(1S). It is shown that the quantum yield of O(1S) depends on the ratio of electron density to atomic oxygen density. This suggests that the quantum yield of O(1S) may depend on the degree of vibrational excitation of the recombining O2(+). The quantum yield of O(1D) has been measured to be 1.23 + or - 0.42, with no dependence on the electron-oxygen ratio.

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

PubMed

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M; Alsari, Mejd; Booker, Edward P; Hutter, Eline M; Pearson, Andrew J; Lilliu, Samuele; Savenije, Tom J; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H; Stranks, Samuel D

2018-03-21

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

Weak value amplification considered harmful

NASA Astrophysics Data System (ADS)

Ferrie, Christopher; Combes, Joshua

2014-03-01

We show using statistically rigorous arguments that the technique of weak value amplification does not perform better than standard statistical techniques for the tasks of parameter estimation and signal detection. We show that using all data and considering the joint distribution of all measurement outcomes yields the optimal estimator. Moreover, we show estimation using the maximum likelihood technique with weak values as small as possible produces better performance for quantum metrology. In doing so, we identify the optimal experimental arrangement to be the one which reveals the maximal eigenvalue of the square of system observables. We also show these conclusions do not change in the presence of technical noise.

Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire.

PubMed

Li, Qiang; Wei, Hong; Xu, Hongxing

2015-12-09

The interactions between surface plasmons (SPs) in metal nanostructures and excitons in quantum emitters (QEs) lead to many interesting phenomena and potential applications that are strongly dependent on the quantum yield of SPs. The difficulty in distinguishing all the possible exciton recombination channels hinders the experimental determination of SP quantum yield. Here, we experimentally measured for the first time the quantum yield of single SPs generated by the exciton-plasmon coupling in a system composed of a single quantum dot and a silver nanowire (NW). By utilizing the SP guiding property of the NW, the decay rates of all the exciton recombination channels, i.e., direct free space radiation channel, SP generation channel, and nonradiative damping channel, are quantitatively obtained. It is determined that the optimum emitter-NW coupling distance for the largest SP quantum yield is about 10 nm, resulting from the different distance-dependent decay rates of the three channels. These results are important for manipulating the coupling between plasmonic nanostructures and QEs and developing on-chip quantum plasmonic devices for potential nanophotonic and quantum information applications.

Absolute quantum yield measurement of powder samples.

PubMed

Moreno, Luis A

2012-05-12

Measurement of fluorescence quantum yield has become an important tool in the search for new solutions in the development, evaluation, quality control and research of illumination, AV equipment, organic EL material, films, filters and fluorescent probes for bio-industry. Quantum yield is calculated as the ratio of the number of photons absorbed, to the number of photons emitted by a material. The higher the quantum yield, the better the efficiency of the fluorescent material. For the measurements featured in this video, we will use the Hitachi F-7000 fluorescence spectrophotometer equipped with the Quantum Yield measuring accessory and Report Generator program. All the information provided applies to this system. Measurement of quantum yield in powder samples is performed following these steps: 1. Generation of instrument correction factors for the excitation and emission monochromators. This is an important requirement for the correct measurement of quantum yield. It has been performed in advance for the full measurement range of the instrument and will not be shown in this video due to time limitations. 2. Measurement of integrating sphere correction factors. The purpose of this step is to take into consideration reflectivity characteristics of the integrating sphere used for the measurements. 3. Reference and Sample measurement using direct excitation and indirect excitation. 4. Quantum Yield calculation using Direct and Indirect excitation. Direct excitation is when the sample is facing directly the excitation beam, which would be the normal measurement setup. However, because we use an integrating sphere, a portion of the emitted photons resulting from the sample fluorescence are reflected by the integrating sphere and will re-excite the sample, so we need to take into consideration indirect excitation. This is accomplished by measuring the sample placed in the port facing the emission monochromator, calculating indirect quantum yield and correcting the direct quantum yield calculation. 5. Corrected quantum yield calculation. 6. Chromaticity coordinates calculation using Report Generator program. The Hitachi F-7000 Quantum Yield Measurement System offer advantages for this application, as follows: High sensitivity (S/N ratio 800 or better RMS). Signal is the Raman band of water measured under the following conditions: Ex wavelength 350 nm, band pass Ex and Em 5 nm, response 2 sec), noise is measured at the maximum of the Raman peak. High sensitivity allows measurement of samples even with low quantum yield. Using this system we have measured quantum yields as low as 0.1 for a sample of salicylic acid and as high as 0.8 for a sample of magnesium tungstate. Highly accurate measurement with a dynamic range of 6 orders of magnitude allows for measurements of both sharp scattering peaks with high intensity, as well as broad fluorescence peaks of low intensity under the same conditions. High measuring throughput and reduced light exposure to the sample, due to a high scanning speed of up to 60,000 nm/minute and automatic shutter function. Measurement of quantum yield over a wide wavelength range from 240 to 800 nm. Accurate quantum yield measurements are the result of collecting instrument spectral response and integrating sphere correction factors before measuring the sample. Large selection of calculated parameters provided by dedicated and easy to use software. During this video we will measure sodium salicylate in powder form which is known to have a quantum yield value of 0.4 to 0.5.

Optimal single-shot strategies for discrimination of quantum measurements

NASA Astrophysics Data System (ADS)

Sedlák, Michal; Ziman, Mário

2014-11-01

We study discrimination of m quantum measurements in the scenario when the unknown measurement with n outcomes can be used only once. We show that ancilla-assisted discrimination procedures provide a nontrivial advantage over simple (ancilla-free) schemes for perfect distinguishability and we prove that inevitably m ≤n . We derive necessary and sufficient conditions of perfect distinguishability of general binary measurements. We show that the optimization of the discrimination of projective qubit measurements and their mixtures with white noise is equivalent to the discrimination of specific quantum states. In particular, the optimal protocol for discrimination of projective qubit measurements with fixed failure rate (exploiting maximally entangled test state) is described. While minimum-error discrimination of two projective qubit measurements can be realized without any need of entanglement, we show that discrimination of three projective qubit measurements requires a bipartite probe state. Moreover, when the measurements are not projective, the non-maximally entangled test states can outperform the maximally entangled ones. Finally, we rephrase the unambiguous discrimination of measurements as quantum key distribution protocol.

A New Quantum Proxy Multi-signature Scheme Using Maximally Entangled Seven-Qubit States

NASA Astrophysics Data System (ADS)

Cao, Hai-Jing; Zhang, Jia-Fu; Liu, Jian; Li, Zeng-You

2016-02-01

In this paper, we propose a new secure quantum proxy multi-signature scheme using seven-qubit entangled quantum state as quantum channels, which may have applications in e-payment system, e-government, e-business, etc. This scheme is based on controlled quantum teleportation. The scheme uses the physical characteristics of quantum mechanics to guarantee its anonymity, verifiability, traceability, unforgetability and undeniability.

Entanglement Equilibrium and the Einstein Equation.

PubMed

Jacobson, Ted

2016-05-20

A link between the semiclassical Einstein equation and a maximal vacuum entanglement hypothesis is established. The hypothesis asserts that entanglement entropy in small geodesic balls is maximized at fixed volume in a locally maximally symmetric vacuum state of geometry and quantum fields. A qualitative argument suggests that the Einstein equation implies the validity of the hypothesis. A more precise argument shows that, for first-order variations of the local vacuum state of conformal quantum fields, the vacuum entanglement is stationary if and only if the Einstein equation holds. For nonconformal fields, the same conclusion follows modulo a conjecture about the variation of entanglement entropy.

Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Xuedan; Diroll, Benjamin T.; Cho, Wooje

Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g( 2)(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicatingmore » the importance of surface passivation on NPL emission quality. Second-order photon correlation (g( 2)(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. In conclusion, these findings reveal that by careful growth control and core–shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications.« less

Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets

DOE PAGES

Ma, Xuedan; Diroll, Benjamin T.; Cho, Wooje; ...

2017-08-08

Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g( 2)(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicatingmore » the importance of surface passivation on NPL emission quality. Second-order photon correlation (g( 2)(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. In conclusion, these findings reveal that by careful growth control and core–shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications.« less

Measures of disturbance and incompatibility for quantum measurements

NASA Astrophysics Data System (ADS)

Mandayam, Prabha; Srinivas, M. D.

2014-06-01

We propose a class of incompatibility measures for quantum observables based on quantifying the effect of a measurement of one observable on the statistics of the outcomes of another. Specifically, for a pair of observables A and B with purely discrete spectra, we compare the following two probability distributions: one resulting from a measurement of A followed by a measurement of B on a given state and the other obtained from a measurement of B alone on the same state. We show that maximizing the distance between these two distributions over all states yields a valid measure of the incompatibility of observables A and B, which is zero if and only if they commute and is strictly greater than zero (and less than or equal to one) otherwise. For finite-dimensional systems, we obtain a tight upper bound on the incompatibility of any pair of observables and show that the bound is attained when the observables are totally nondegenerate and associated with mutually unbiased bases. In the process, we also establish an important relation between the incompatibility of a pair of observables and the maximal disturbances due to their measurements. Finally, we indicate how these measures of incompatibility and disturbance can be extended to the more general class of nonprojective measurements. In particular, we obtain a nontrivial upper bound on the incompatibility of one Lüders instrument with another.

Beating the Clauser-Horne-Shimony-Holt and the Svetlichny games with optimal states

NASA Astrophysics Data System (ADS)

Su, Hong-Yi; Ren, Changliang; Chen, Jing-Ling; Zhang, Fu-Lin; Wu, Chunfeng; Xu, Zhen-Peng; Gu, Mile; Vinjanampathy, Sai; Kwek, L. C.

2016-02-01

We study the relation between the maximal violation of Svetlichny's inequality and the mixedness of quantum states and obtain the optimal state (i.e., maximally nonlocal mixed states, or MNMS, for each value of linear entropy) to beat the Clauser-Horne-Shimony-Holt and the Svetlichny games. For the two-qubit and three-qubit MNMS, we showed that these states are also the most tolerant state against white noise, and thus serve as valuable quantum resources for such games. In particular, the quantum prediction of the MNMS decreases as the linear entropy increases, and then ceases to be nonlocal when the linear entropy reaches the critical points 2 /3 and 9 /14 for the two- and three-qubit cases, respectively. The MNMS are related to classical errors in experimental preparation of maximally entangled states.

Quantum secret sharing for a general quantum access structure

NASA Astrophysics Data System (ADS)

Bai, Chen-Ming; Li, Zhi-Hui; Si, Meng-Meng; Li, Yong-Ming

2017-10-01

Quantum secret sharing is a procedure for sharing a secret among a number of participants such that only certain subsets of participants can collaboratively reconstruct it, which are called authorized sets. The quantum access structure of a secret sharing is a family of all authorized sets. Firstly, in this paper, we propose the concept of decomposition of quantum access structure to design a quantum secret sharing scheme. Secondly, based on a maximal quantum access structure (MQAS) [D. Gottesman, Phys. Rev. A 61, 042311 (2000)], we propose an algorithm to improve a MQAS and obtain an improved maximal quantum access structure (IMQAS). Then, we present a sufficient and necessary condition about IMQAS, which shows the relationship between the minimal authorized sets and the players. In accordance with properties, we construct an efficient quantum secret sharing scheme with a decomposition and IMQAS. A major advantage of these techniques is that it allows us to construct a method to realize a general quantum access structure. Finally, we present two kinds of quantum secret sharing schemes via the thought of concatenation or a decomposition of quantum access structure. As a consequence, we find that the application of these techniques allows us to save more quantum shares and reduces more cost than the existing scheme.

Effect of site disorder on the ground state of a frustrated spin dimer quantum magnet

NASA Astrophysics Data System (ADS)

Hristov, Alexander; Shapiro, Maxwell; Lee, Minseong; Rodenbach, Linsey; Choi, Eun Sang; Park, Ju-Hyun; Munsie, Tim; Luke, Graeme; Fisher, Ian

Ba3Mn2O8 is a geometrically frustrated spin dimer quantum magnet. Pairs of Mn 5+ (S = 1) ions are strongly coupled via antiferromagnetic exchange to yield a singlet ground state, with excited triplet and quintuplet states. Isovalent substitution of V5+ (S = 0) for Mn breaks dimers, resulting in unpaired S = 1 spins, the ground state of which is investigated here for compositions spanning the range 0 <= x <= 1 of Ba3(Mn1-xVx)2O8. From a theoretical perspective, for dimers occupying an unfrustrated bipartite lattice, such site disorder is anticipated to yield long range magnetism for unpaired Mn spins both in the dilute limit where x is small, a phenomena known as order-by-disorder, and in the proximity of x = 1 / 2 where the system is maximally disordered and close to a percolation threshold. In this frustrated system, however, our experiments find evidence of spin freezing for six compositions 0 . 05 <= x <= 0 . 85 . In this regime, we find entropy removed at an energy scale independent of the freezing temperature. We discuss the possibility of a spin-glass to random singlet transition for critical compositions in the two dilute limits x -> 0 and x -> 1 . NSF DMR-Award 1205165.

Maps on positive operators preserving Rényi type relative entropies and maximal f-divergences

NASA Astrophysics Data System (ADS)

Gaál, Marcell; Nagy, Gergő

2018-02-01

In this paper, we deal with two quantum relative entropy preserver problems on the cones of positive (either positive definite or positive semidefinite) operators. The first one is related to a quantum Rényi relative entropy like quantity which plays an important role in classical-quantum channel decoding. The second one is connected to the so-called maximal f-divergences introduced by D. Petz and M. B. Ruskai who considered this quantity as a generalization of the usual Belavkin-Staszewski relative entropy. We emphasize in advance that all the results are obtained for finite-dimensional Hilbert spaces.

Variation in canopy duration in the perennial biofuel crop Miscanthus reveals complex associations with yield.

PubMed

Robson, Paul R H; Farrar, Kerrie; Gay, Alan P; Jensen, Elaine F; Clifton-Brown, John C; Donnison, Iain S

2013-05-01

Energy crops can provide a sustainable source of power and fuels, and mitigate the negative effects of CO2 emissions associated with fossil fuel use. Miscanthus is a perennial C4 energy crop capable of producing large biomass yields whilst requiring low levels of input. Miscanthus is largely unimproved and therefore there could be significant opportunities to increase yield. Further increases in yield will improve the economics, energy balance, and carbon mitigation of the crop, as well as reducing land-take. One strategy to increase yield in Miscanthus is to maximize the light captured through an extension of canopy duration. In this study, canopy duration was compared among a diverse collection of 244 Miscanthus genotypes. Canopy duration was determined by calculating the number of days between canopy establishment and senescence. Yield was positively correlated with canopy duration. Earlier establishment and later senescence were also both separately correlated with higher yield. However, although genotypes with short canopy durations were low yielding, not all genotypes with long canopy durations were high yielding. Differences of yield between genotypes with long canopy durations were associated with variation in stem and leaf traits. Different methodologies to assess canopy duration traits were investigated, including visual assessment, image analysis, light interception, and different trait thresholds. The highest correlation coefficients were associated with later assessments of traits and the use of quantum sensors for canopy establishment. A model for trait optimization to enable yield improvement in Miscanthus and other bioenergy crops is discussed.

Variation in canopy duration in the perennial biofuel crop Miscanthus reveals complex associations with yield

PubMed Central

Robson, Paul R.H.; Farrar, Kerrie; Gay, Alan P.; Jensen, Elaine F.; Clifton-Brown, John C.; Donnison, Iain S.

2013-01-01

Energy crops can provide a sustainable source of power and fuels, and mitigate the negative effects of CO2 emissions associated with fossil fuel use. Miscanthus is a perennial C4 energy crop capable of producing large biomass yields whilst requiring low levels of input. Miscanthus is largely unimproved and therefore there could be significant opportunities to increase yield. Further increases in yield will improve the economics, energy balance, and carbon mitigation of the crop, as well as reducing land-take. One strategy to increase yield in Miscanthus is to maximize the light captured through an extension of canopy duration. In this study, canopy duration was compared among a diverse collection of 244 Miscanthus genotypes. Canopy duration was determined by calculating the number of days between canopy establishment and senescence. Yield was positively correlated with canopy duration. Earlier establishment and later senescence were also both separately correlated with higher yield. However, although genotypes with short canopy durations were low yielding, not all genotypes with long canopy durations were high yielding. Differences of yield between genotypes with long canopy durations were associated with variation in stem and leaf traits. Different methodologies to assess canopy duration traits were investigated, including visual assessment, image analysis, light interception, and different trait thresholds. The highest correlation coefficients were associated with later assessments of traits and the use of quantum sensors for canopy establishment. A model for trait optimization to enable yield improvement in Miscanthus and other bioenergy crops is discussed. PMID:23599277

Absolute I(asterisk) quantum yields for the ICN A state by diode laser gain-vs-absorption spectroscopy

NASA Technical Reports Server (NTRS)

Hess, Wayne P.; Leone, Stephen R.

1987-01-01

Absolute I(asterisk) quantum yields have been measured as a function of wavelength for room temperature photodissociation of the ICN A state continuum. The yields are obtained by the technique of time-resolved diode laser gain-vs-absorption spectroscopy. Quantum yields are evaluated at seven wavelengths from 248 to 284 nm. The yield at 266 nm is 66.0 + or - 2 percent and it falls off to 53.4 + or - 2 percent and 44.0 + or - 4 percent at 284 and 248 nm, respectively. The latter values are significantly higher than those obtained by previous workers using infrared fluorescence. Estimates of I(asterisk) quantum yields obtained from analysis of CN photofragment rotational distributions, as discussed by other workers, are in good agreement with the I(asterisk) yields reported here. The results are considered in conjunction with recent theoretical and experimental work on the CN rotational distributions and with previous I(asterisk) quantum yield results.

Unity quantum yield of photogenerated charges and band-like transport in quantum-dot solids.

PubMed

Talgorn, Elise; Gao, Yunan; Aerts, Michiel; Kunneman, Lucas T; Schins, Juleon M; Savenije, T J; van Huis, Marijn A; van der Zant, Herre S J; Houtepen, Arjan J; Siebbeles, Laurens D A

2011-09-25

Solid films of colloidal quantum dots show promise in the manufacture of photodetectors and solar cells. These devices require high yields of photogenerated charges and high carrier mobilities, which are difficult to achieve in quantum-dot films owing to a strong electron-hole interaction and quantum confinement. Here, we show that the quantum yield of photogenerated charges in strongly coupled PbSe quantum-dot films is unity over a large temperature range. At high photoexcitation density, a transition takes place from hopping between localized states to band-like transport. These strongly coupled quantum-dot films have electrical properties that approach those of crystalline bulk semiconductors, while retaining the size tunability and cheap processing properties of colloidal quantum dots.

Ecophysiological and metabolic responses to interactive exposure to nutrients and copper excess in the brown macroalga Cystoseira tamariscifolia.

PubMed

Celis-Plá, Paula S M; Brown, Murray T; Santillán-Sarmiento, Alex; Korbee, Nathalie; Sáez, Claudio A; Figueroa, Félix L

2018-03-01

Global scenarios evidence that contamination due to anthropogenic activities occur at different spatial-temporal scales, being important stressors: eutrophication, due to increased nutrient inputs; and metal pollution, mostly derived from industrial activities. In this study, we investigated ecophysiological and metabolic responses to copper and nutrient excess in the brown macroalga Cystoseira tamariscifolia. Whole plants were incubated in an indoor system under control conditions, two levels of nominal copper (0.5 and 2.0μM), and two levels of nutrient supply for two weeks. Maximal quantum yield (F v /F m ) and maximal electron transport rate (ETR max ) increased under copper exposure. Photosynthetic pigments and phenolic compounds (PC) increased under the highest copper levels. The intra-cellular copper content increased under high copper exposure in both nutrient conditions. C. tamariscifolia from the Atlantic displayed efficient metal exclusion mechanisms, since most of the total copper accumulated by the cell was bound to the cell wall. Copyright © 2018 Elsevier Ltd. All rights reserved.

Drop-in compatible entanglement for optical-fiber networks.

PubMed

Hall, Matthew A; Altepeter, Joseph B; Kumar, Prem

2009-08-17

A growing number of quantum communication protocols require entanglement distribution among remote parties, which is best accomplished by exploiting the mature technology and extensive infrastructure of low-loss optical fiber. For this reason, a practical source of entangled photons must be drop-in compatible with optical fiber networks. Here we demonstrate such a source for the first time, in which the nonlinearity of standard single-mode fiber is utilized to yield entangled photon pairs in the 1310-nm O-band. Using an ultra-stable design, we produce polarization entanglement with 98.0% +/- 0.5% fidelity to a maximally entangled state as characterized via coincidence-basis tomography. To demonstrate the source's drop-in capability, we transmit one photon from each entangled pair through a telecommunications-grade optical amplifier set to boost classical 1550-nm (C-band) communication signals. We verify that the photon pairs experience no measurable decoherence upon passing through the active amplifier (the output state's fidelity with a maximally entangled state is 98.4% +/- 1.4%). (c) 2009 Optical Society of America

Interactive effects of cadmium and acid rain on photosynthetic light reaction in soybean seedlings.

PubMed

Sun, Zhaoguo; Wang, Lihong; Chen, Minmin; Wang, Lei; Liang, Chanjuan; Zhou, Qing; Huang, Xiaohua

2012-05-01

Interactive effects of cadmium (Cd(2+)) and acid rain on photosynthetic light reaction in soybean seedlings were investigated under hydroponic conditions. Single treatment with Cd(2+) or acid rain and the combined treatment decreased the content of chlorophyll, Hill reaction rate, the activity of Mg(2+)-ATPase, maximal photochemical efficiency and maximal quantum yield, increased initial fluorescence and damaged the chloroplast structure in soybean seedlings. In the combined treatment, the change in the photosynthetic parameters and the damage of chloroplast structure were stronger than those of any single pollution. Meanwhile, Cd(2+) and acid rain had the interactive effects on the test indices in soybean seedlings. The results indicated that the combined pollution of Cd(2+) and acid rain aggravated the toxic effect of the single pollution of Cd(2+) or acid rain on the photosynthetic parameters due to the serious damage to the chloroplast structure. Copyright © 2011 Elsevier Inc. All rights reserved.

Hidden Quantum Processes, Quantum Ion Channels, and 1/ fθ-Type Noise.

PubMed

Paris, Alan; Vosoughi, Azadeh; Berman, Stephen A; Atia, George

2018-07-01

In this letter, we perform a complete and in-depth analysis of Lorentzian noises, such as those arising from [Formula: see text] and [Formula: see text] channel kinetics, in order to identify the source of [Formula: see text]-type noise in neurological membranes. We prove that the autocovariance of Lorentzian noise depends solely on the eigenvalues (time constants) of the kinetic matrix but that the Lorentzian weighting coefficients depend entirely on the eigenvectors of this matrix. We then show that there are rotations of the kinetic eigenvectors that send any initial weights to any target weights without altering the time constants. In particular, we show there are target weights for which the resulting Lorenztian noise has an approximately [Formula: see text]-type spectrum. We justify these kinetic rotations by introducing a quantum mechanical formulation of membrane stochastics, called hidden quantum activated-measurement models, and prove that these quantum models are probabilistically indistinguishable from the classical hidden Markov models typically used for ion channel stochastics. The quantum dividend obtained by replacing classical with quantum membranes is that rotations of the Lorentzian weights become simple readjustments of the quantum state without any change to the laboratory-determined kinetic and conductance parameters. Moreover, the quantum formalism allows us to model the activation energy of a membrane, and we show that maximizing entropy under constrained activation energy yields the previous [Formula: see text]-type Lorentzian weights, in which the spectral exponent [Formula: see text] is a Lagrange multiplier for the energy constraint. Thus, we provide a plausible neurophysical mechanism by which channel and membrane kinetics can give rise to [Formula: see text]-type noise (something that has been occasionally denied in the literature), as well as a realistic and experimentally testable explanation for the numerical values of the spectral exponents. We also discuss applications of quantum membranes beyond [Formula: see text]-type -noise, including applications to animal models and possible impact on quantum foundations.

Enhancing non-local correlations in the bipartite partitions of two qubit-system with non-mutual interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, A.-B.A., E-mail: abdelbastm@yahoo.com; Faculty of Science, Assiut University, Assiut; Joshi, A., E-mail: mcbamji@gmail.com

2016-03-15

Several quantum-mechanical correlations, notably, quantum entanglement, measurement-induced nonlocality and Bell nonlocality are studied for a two qubit-system having no mutual interaction. Analytical expressions for the measures of these quantum-mechanical correlations of different bipartite partitions of the system are obtained, for initially two entangled qubits and the two photons are in their vacuum states. It is found that the qubits-fields interaction leads to the loss and gain of the initial quantum correlations. The lost initial quantum correlations transfer from the qubits to the cavity fields. It is found that the maximal violation of Bell’s inequality is occurring when the quantum correlationsmore » of both the logarithmic negativity and measurement-induced nonlocality reach particular values. The maximal violation of Bell’s inequality occurs only for certain bipartite partitions of the system. The frequency detuning leads to quick oscillations of the quantum correlations and inhibits their transfer from the qubits to the cavity modes. It is also found that the dynamical behavior of the quantum correlation clearly depends on the qubit distribution angle.« less

Control of Emission Color of High Quantum Yield CH3NH3PbBr3 Perovskite Quantum Dots by Precipitation Temperature.

PubMed

Huang, He; Susha, Andrei S; Kershaw, Stephen V; Hung, Tak Fu; Rogach, Andrey L

2015-09-01

Emission color controlled, high quantum yield CH 3 NH 3 PbBr 3 perovskite quantum dots are obtained by changing the temperature of a bad solvent during synthesis. The products for temperatures between 0 and 60 °C have good spectral purity with narrow emission line widths of 28-36 nm, high absolute emission quantum yields of 74% to 93%, and short radiative lifetimes of 13-27 ns.

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

NASA Astrophysics Data System (ADS)

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

2018-03-01

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakes.

PubMed

Lin, Liangxu; Zhang, Shaowei

2012-10-21

We have developed an effective method to exfoliate and disintegrate multi-walled carbon nanotubes and graphite flakes. With this technique, high yield production of luminescent graphene quantum dots with high quantum yield and low oxidization can be achieved.

Note: Measuring instrument of singlet oxygen quantum yield in photodynamic effects

NASA Astrophysics Data System (ADS)

Li, Zhongwei; Zhang, Pengwei; Zang, Lixin; Qin, Feng; Zhang, Zhiguo; Zhang, Hongli

2017-06-01

Using diphenylisobenzofuran (C20H14O) as a singlet oxygen (1O2) reporter, a comparison method, which can be used to measure the singlet oxygen quantum yield (ΦΔ) of the photosensitizer quantitatively, is presented in this paper. Based on this method, an automatic measuring instrument of singlet oxygen quantum yield is developed. The singlet oxygen quantum yield of the photosensitizer hermimether and aloe-emodin is measured. It is found that the measuring results are identical to the existing ones, which verifies the validity of the measuring instrument.

Maximal temperature in a simple thermodynamical system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, De-Chang; Stojkovic, Dejan, E-mail: diedachung@gmail.com, E-mail: ds77@buffalo.edu

Temperature in a simple thermodynamical system is not limited from above. It is also widely believed that it does not make sense talking about temperatures higher than the Planck temperature in the absence of the full theory of quantum gravity. Here, we demonstrate that there exist a maximal achievable temperature in a system where particles obey the laws of quantum mechanics and classical gravity before we reach the realm of quantum gravity. Namely, if two particles with a given center of mass energy come at the distance shorter than the Schwarzschild diameter apart, according to classical gravity they will formmore » a black hole. It is possible to calculate that a simple thermodynamical system will be dominated by black holes at a critical temperature which is about three times lower than the Planck temperature. That represents the maximal achievable temperature in a simple thermodynamical system.« less

Test of mutually unbiased bases for six-dimensional photonic quantum systems

PubMed Central

D'Ambrosio, Vincenzo; Cardano, Filippo; Karimi, Ebrahim; Nagali, Eleonora; Santamato, Enrico; Marrucci, Lorenzo; Sciarrino, Fabio

2013-01-01

In quantum information, complementarity of quantum mechanical observables plays a key role. The eigenstates of two complementary observables form a pair of mutually unbiased bases (MUBs). More generally, a set of MUBs consists of bases that are all pairwise unbiased. Except for specific dimensions of the Hilbert space, the maximal sets of MUBs are unknown in general. Even for a dimension as low as six, the identification of a maximal set of MUBs remains an open problem, although there is strong numerical evidence that no more than three simultaneous MUBs do exist. Here, by exploiting a newly developed holographic technique, we implement and test different sets of three MUBs for a single photon six-dimensional quantum state (a “qusix”), encoded exploiting polarization and orbital angular momentum of photons. A close agreement is observed between theory and experiments. Our results can find applications in state tomography, quantitative wave-particle duality, quantum key distribution. PMID:24067548

Test of mutually unbiased bases for six-dimensional photonic quantum systems.

PubMed

D'Ambrosio, Vincenzo; Cardano, Filippo; Karimi, Ebrahim; Nagali, Eleonora; Santamato, Enrico; Marrucci, Lorenzo; Sciarrino, Fabio

2013-09-25

In quantum information, complementarity of quantum mechanical observables plays a key role. The eigenstates of two complementary observables form a pair of mutually unbiased bases (MUBs). More generally, a set of MUBs consists of bases that are all pairwise unbiased. Except for specific dimensions of the Hilbert space, the maximal sets of MUBs are unknown in general. Even for a dimension as low as six, the identification of a maximal set of MUBs remains an open problem, although there is strong numerical evidence that no more than three simultaneous MUBs do exist. Here, by exploiting a newly developed holographic technique, we implement and test different sets of three MUBs for a single photon six-dimensional quantum state (a "qusix"), encoded exploiting polarization and orbital angular momentum of photons. A close agreement is observed between theory and experiments. Our results can find applications in state tomography, quantitative wave-particle duality, quantum key distribution.

Generalized Steering Robustness of Bipartite Quantum States

NASA Astrophysics Data System (ADS)

Zheng, Chunming; Guo, Zhihua; Cao, Huaixin

2018-06-01

EPR steering is a kind of quantum correlation that is intermediate between entanglement and Bell nonlocality. In this paper, by recalling the definitions of unsteerability and steerability, some properties of them are given, e.g, it is proved that a local quantum channel transforms every unsteerable state into an unsteerable state. Second, a way of quantifying quantum steering, which we called the generalized steering robustness (GSR), is introduced and some interesting properties are established, including: (1) GSR of a state vanishes if and only if the state is unsteerable; (2) a local quantum channel does not increase GSR of any state; (3) GSR is invariant under each local unitary operation; (4) as a function on the state space, GSR is convex and lower-semi continuous. Lastly, by using the majorization between the reduced states of two pure states, GSR of the two pure states are compared, and it is proved that every maximally entangled state has the maximal GSR.

Gaussian private quantum channel with squeezed coherent states

PubMed Central

Jeong, Kabgyun; Kim, Jaewan; Lee, Su-Yong

2015-01-01

While the objective of conventional quantum key distribution (QKD) is to secretly generate and share the classical bits concealed in the form of maximally mixed quantum states, that of private quantum channel (PQC) is to secretly transmit individual quantum states concealed in the form of maximally mixed states using shared one-time pad and it is called Gaussian private quantum channel (GPQC) when the scheme is in the regime of continuous variables. We propose a GPQC enhanced with squeezed coherent states (GPQCwSC), which is a generalization of GPQC with coherent states only (GPQCo) [Phys. Rev. A 72, 042313 (2005)]. We show that GPQCwSC beats the GPQCo for the upper bound on accessible information. As a subsidiary example, it is shown that the squeezed states take an advantage over the coherent states against a beam splitting attack in a continuous variable QKD. It is also shown that a squeezing operation can be approximated as a superposition of two different displacement operations in the small squeezing regime. PMID:26364893

Quantum teleportation via noisy bipartite and tripartite accelerating quantum states: beyond the single mode approximation

NASA Astrophysics Data System (ADS)

Zounia, M.; Shamirzaie, M.; Ashouri, A.

2017-09-01

In this paper quantum teleportation of an unknown quantum state via noisy maximally bipartite (Bell) and maximally tripartite (Greenberger-Horne-Zeilinger (GHZ)) entangled states are investigated. We suppose that one of the observers who would receive the sent state accelerates uniformly with respect to the sender. The interactions of the quantum system with its environment during the teleportation process impose noises. These (unital and nonunital) noises are: phase damping, phase flip, amplitude damping and bit flip. In expressing the modes of the Dirac field used as qubits, in the accelerating frame, the so-called single mode approximation is not imposed. We calculate the fidelities of teleportation, and discuss their behaviors using suitable plots. The effects of noise, acceleration and going beyond the single mode approximation are discussed. Although the Bell states bring higher fidelities than GHZ states, the global behaviors of the two quantum systems with respect to some noise types, and therefore their fidelities, are different.

Gaussian private quantum channel with squeezed coherent states.

PubMed

Jeong, Kabgyun; Kim, Jaewan; Lee, Su-Yong

2015-09-14

While the objective of conventional quantum key distribution (QKD) is to secretly generate and share the classical bits concealed in the form of maximally mixed quantum states, that of private quantum channel (PQC) is to secretly transmit individual quantum states concealed in the form of maximally mixed states using shared one-time pad and it is called Gaussian private quantum channel (GPQC) when the scheme is in the regime of continuous variables. We propose a GPQC enhanced with squeezed coherent states (GPQCwSC), which is a generalization of GPQC with coherent states only (GPQCo) [Phys. Rev. A 72, 042313 (2005)]. We show that GPQCwSC beats the GPQCo for the upper bound on accessible information. As a subsidiary example, it is shown that the squeezed states take an advantage over the coherent states against a beam splitting attack in a continuous variable QKD. It is also shown that a squeezing operation can be approximated as a superposition of two different displacement operations in the small squeezing regime.

Quantum Yields in Mixed-Conifer Forests and Ponderosa Pine Plantations

NASA Astrophysics Data System (ADS)

Wei, L.; Marshall, J. D.; Zhang, J.

2008-12-01

Most process-based physiological models require canopy quantum yield of photosynthesis as a starting point to simulate carbon sequestration and subsequently gross primary production (GPP). The quantum yield is a measure of photosynthetic efficiency expressed in moles of CO2 assimilated per mole of photons absorbed; the process is influenced by environmental factors. In the summer 2008, we measured quantum yields on both sun and shade leaves for four conifer species at five sites within Mica Creek Experimental Watershed (MCEW) in northern Idaho and one conifer species at three sites in northern California. The MCEW forest is typical of mixed conifer stands dominated by grand fir (Abies grandis (Douglas ex D. Don) Lindl.). In northern California, the three sites with contrasting site qualities are ponderosa pine (Pinus ponderosa C. Lawson var. ponderosa) plantations that were experimentally treated with vegetation control, fertilization, and a combination of both. We found that quantum yields in MCEW ranged from ~0.045 to ~0.075 mol CO2 per mol incident photon. However, there were no significant differences between canopy positions, or among sites or tree species. In northern California, the mean value of quantum yield of three sites was 0.051 mol CO2/mol incident photon. No significant difference in quantum yield was found between canopy positions, or among treatments or sites. The results suggest that these conifer species maintain relatively consistent quantum yield in both MCEW and northern California. This consistency simplifies the use of a process-based model to accurately predict forest productivity in these areas.

Maximally-localized position, Euclidean path-integral, and thermodynamics in GUP quantum mechanics

NASA Astrophysics Data System (ADS)

Bernardo, Reginald Christian S.; Esguerra, Jose Perico H.

2018-04-01

In dealing with quantum mechanics at very high energies, it is essential to adapt to a quasiposition representation using the maximally-localized states because of the generalized uncertainty principle. In this paper, we look at maximally-localized states as eigenstates of the operator ξ = X + iβP that we refer to as the maximally-localized position. We calculate the overlap between maximally-localized states and show that the identity operator can be expressed in terms of the maximally-localized states. Furthermore, we show that the maximally-localized position is diagonal in momentum-space and that the maximally-localized position and its adjoint satisfy commutation and anti-commutation relations reminiscent of the harmonic oscillator commutation and anti-commutation relations. As application, we use the maximally-localized position in developing the Euclidean path-integral and introduce the compact form of the propagator for maximal localization. The free particle momentum-space propagator and the propagator for maximal localization are analytically evaluated up to quadratic-order in β. Finally, we obtain a path-integral expression for the partition function of a thermodynamic system using the maximally-localized states. The partition function of a gas of noninteracting particles is evaluated. At temperatures exceeding the Planck energy, we obtain the gas' maximum internal energy N / 2 β and recover the zero heat capacity of an ideal gas.

Physics considerations in MV-CBCT multi-layer imager design.

PubMed

Hu, Yue-Houng; Fueglistaller, Rony; Myronakis, Marios E; Rottmann, Joerg; Wang, Adam; Shedlock, Daniel; Morf, Daniel; Baturin, Paul; Huber, Pascal; Star-Lack, Josh M; Berbeco, Ross I

2018-05-30

Megavoltage (MV) cone-beam computed tomography (CBCT) using an electronic portal imaging (EPID) offers advantageous features, including 3D mapping, treatment beam registration, high-z artifact suppression, and direct radiation dose calculation. Adoption has been slowed by image quality limitations and concerns about imaging dose. Developments in imager design, including pixelated scintillators, structured phosphors, inexpensive scintillation materials, and multi-layer imager (MLI) architecture have been explored to improve EPID image quality and reduce imaging dose. The present study employs a hybrid Monte Carlo and linear systems model to determine the effect of detector design elements, such as multi-layer architecture and scintillation materials. We follow metrics of image quality including modulation transfer function (MTF) and noise power spectrum (NPS) from projection images to 3D reconstructions to in-plane slices and apply a task based figure-of-merit, the ideal observer signal-to-noise ratio (d') to determine the effect of detector design on object detectability. Generally, detectability was limited by detector noise performance. Deploying an MLI imager with a single scintillation material for all layers yields improvement in noise performance and d' linear with the number of layers. In general, improving x-ray absorption using thicker scintillators results in improved DQE(0). However, if light yield is low, performance will be affected by electronic noise at relatively high doses, resulting in rapid image quality degradation. Maximizing image quality in a heterogenous MLI detector (i.e. multiple different scintillation materials) is most affected by limiting imager noise. However, while a second-order effect, maximizing total spatial resolution of the MLI detector is a balance between the intensity contribution of each layer against its individual MTF. So, while a thinner scintillator may yield a maximal individual-layer MTF, its quantum efficiency will be relatively low in comparison to a thicker scintillator and thus, intensity contribution may be insufficient to noticeably improve the total detector MTF. © 2018 Institute of Physics and Engineering in Medicine.

Absolute 1* quantum yields for the ICN A state by diode laser gain versus absorption spectroscopy

NASA Technical Reports Server (NTRS)

Hess, Wayne P.; Leone, Stephen R.

1987-01-01

Absolute I* quantum yields were measured as a function of wavelength for room temperature photodissociation of the ICN A state continuum. The temperature yields are obtained by the technique of time-resolved diode laser gain-versus-absorption spectroscopy. Quantum yields are evaluated at seven wavelengths from 248 to 284 nm. The yield at 266 nm is 66.0 +/- 2% and it falls off to 53.4 +/- 2% and 44.0 +/- 4% at 284 and 248 respectively. The latter values are significantly higher than those obtained by previous workers using infrared fluorescence. Estimates of I* quantum yields obtained from analysis of CN photofragment rotational distributions, as discussed by other workers, are in good agreement with the I* yields. The results are considered in conjunction with recent theoretical and experimental work on the CN rotational distributions and with previous I* yield results.

Quantum Correlation Properties in Composite Parity-Conserved Matrix Product States

NASA Astrophysics Data System (ADS)

Zhu, Jing-Min

2016-09-01

We give a new thought for constructing long-range quantum correlation in quantum many-body systems. Our proposed composite parity-conserved matrix product state has long-range quantum correlation only for two spin blocks where their spin-block length larger than 1 compared to any subsystem only having short-range quantum correlation, and we investigate quantum correlation properties of two spin blocks varying with environment parameter and spacing spin number. We also find that the geometry quantum discords of two nearest-neighbor spin blocks and two next-nearest-neighbor spin blocks become smaller and for other conditions the geometry quantum discord becomes larger than that in any subcomponent, i.e., the increase or the production of the long-range quantum correlation is at the cost of reducing the short-range quantum correlation compared to the corresponding classical correlation and total correlation having no any characteristic of regulation. For nearest-neighbor and next-nearest-neighbor all the correlations take their maximal values at the same points, while for other conditions no whether for spacing same spin number or for different spacing spin numbers all the correlations taking their maximal values are respectively at different points which are very close. We believe that our work is helpful to comprehensively and deeply understand the organization and structure of quantum correlation especially for long-range quantum correlation of quantum many-body systems; and further helpful for the classification, the depiction and the measure of quantum correlation of quantum many-body systems.

High quantum yield ZnO quantum dots synthesizing via an ultrasonication microreactor method.

PubMed

Yang, Weimin; Yang, Huafang; Ding, Wenhao; Zhang, Bing; Zhang, Le; Wang, Lixi; Yu, Mingxun; Zhang, Qitu

2016-11-01

Green emission ZnO quantum dots were synthesized by an ultrasonic microreactor. Ultrasonic radiation brought bubbles through ultrasonic cavitation. These bubbles built microreactor inside the microreactor. The photoluminescence properties of ZnO quantum dots synthesized with different flow rate, ultrasonic power and temperature were discussed. Flow rate, ultrasonic power and temperature would influence the type and quantity of defects in ZnO quantum dots. The sizes of ZnO quantum dots would be controlled by those conditions as well. Flow rate affected the reaction time. With the increasing of flow rate, the sizes of ZnO quantum dots decreased and the quantum yields first increased then decreased. Ultrasonic power changed the ultrasonic cavitation intensity, which affected the reaction energy and the separation of the solution. With the increasing of ultrasonic power, sizes of ZnO quantum dots first decreased then increased, while the quantum yields kept increasing. The effect of ultrasonic temperature on the photoluminescence properties of ZnO quantum dots was influenced by the flow rate. Different flow rate related to opposite changing trend. Moreover, the quantum yields of ZnO QDs synthesized by ultrasonic microreactor could reach 64.7%, which is higher than those synthesized only under ultrasonic radiation or only by microreactor. Copyright © 2016 Elsevier B.V. All rights reserved.

Maximal qubit violation of n-locality inequalities in a star-shaped quantum network

NASA Astrophysics Data System (ADS)

Andreoli, Francesco; Carvacho, Gonzalo; Santodonato, Luca; Chaves, Rafael; Sciarrino, Fabio

2017-11-01

Bell's theorem was a cornerstone for our understanding of quantum theory and the establishment of Bell non-locality played a crucial role in the development of quantum information. Recently, its extension to complex networks has been attracting growing attention, but a deep characterization of quantum behavior is still missing for this novel context. In this work we analyze quantum correlations arising in the bilocality scenario, that is a tripartite quantum network where the correlations between the parties are mediated by two independent sources of states. First, we prove that non-bilocal correlations witnessed through a Bell-state measurement in the central node of the network form a subset of those obtainable by means of a local projective measurement. This leads us to derive the maximal violation of the bilocality inequality that can be achieved by arbitrary two-qubit quantum states and arbitrary local projective measurements. We then analyze in details the relation between the violation of the bilocality inequality and the CHSH inequality. Finally, we show how our method can be extended to the n-locality scenario consisting of n two-qubit quantum states distributed among n+1 nodes of a star-shaped network.

Maximal violation of a bipartite three-setting, two-outcome Bell inequality using infinite-dimensional quantum systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pal, Karoly F.; Vertesi, Tamas

2010-08-15

The I{sub 3322} inequality is the simplest bipartite two-outcome Bell inequality beyond the Clauser-Horne-Shimony-Holt (CHSH) inequality, consisting of three two-outcome measurements per party. In the case of the CHSH inequality the maximal quantum violation can already be attained with local two-dimensional quantum systems; however, there is no such evidence for the I{sub 3322} inequality. In this paper a family of measurement operators and states is given which enables us to attain the maximum quantum value in an infinite-dimensional Hilbert space. Further, it is conjectured that our construction is optimal in the sense that measuring finite-dimensional quantum systems is not enoughmore » to achieve the true quantum maximum. We also describe an efficient iterative algorithm for computing quantum maximum of an arbitrary two-outcome Bell inequality in any given Hilbert space dimension. This algorithm played a key role in obtaining our results for the I{sub 3322} inequality, and we also applied it to improve on our previous results concerning the maximum quantum violation of several bipartite two-outcome Bell inequalities with up to five settings per party.« less

Degradation Mechanisms in Blue Phosphorescent Organic Light-Emitting Devices by Exciton-Polaron Interactions: Loss in Quantum Yield versus Loss in Charge Balance.

PubMed

Zhang, Yingjie; Aziz, Hany

2017-01-11

We study the relative importance of deterioration of material quantum yield and charge balance to the electroluminescence stability of PHOLEDs, with a special emphasis on blue devices. Investigations show that the quantum yields of both host and emitter in the emission layer degrade due to exciton-polaron interactions and that the deterioration in material quantum yield plays the primary role in device degradation under operation. On the other hand, the results show that the charge balance factor is also affected by exciton-polaron interactions but only plays a secondary role in determining device stability. Finally, we show that the degradation mechanisms in blue PHOLEDs are fundamentally the same as those in green PHOLEDs. The limited stability of the blue devices is a result of faster deterioration in the quantum yield of the emitter.

Maximal yields from multispecies fisheries systems: rules for systems with multiple trophic levels.

PubMed

Matsuda, Hiroyuki; Abrams, Peter A

2006-02-01

Increasing centralization of the control of fisheries combined with increased knowledge of food-web relationships is likely to lead to attempts to maximize economic yield from entire food webs. With the exception of predator-prey systems, we lack any analysis of the nature of such yield-maximizing strategies. We use simple food-web models to investigate the nature of yield- or profit-maximizing exploitation of communities including two types of three-species food webs and a variety of six-species systems with as many as five trophic levels. These models show that, for most webs, relatively few species are harvested at equilibrium and that a significant fraction of the species is lost from the web. These extinctions occur for two reasons: (1) indirect effects due to harvesting of species that had positive effects on the extinct species, and (2) intentional eradication of species that are not themselves valuable, but have negative effects on more valuable species. In most cases, the yield-maximizing harvest involves taking only species from one trophic level. In no case was an unharvested top predator part of the yield-maximizing strategy. Analyses reveal that the existence of direct density dependence in consumers has a large effect on the nature of the optimal harvest policy, typically resulting in harvest of a larger number of species. A constraint that all species must be retained in the system (a "constraint of biodiversity conservation") usually increases the number of species and trophic levels harvested at the yield-maximizing policy. The reduction in total yield caused by such a constraint is modest for most food webs but can be over 90% in some cases. Independent harvesting of species within the web can also cause extinctions but is less likely to do so.

Relating quantum coherence and correlations with entropy-based measures.

PubMed

Wang, Xiao-Li; Yue, Qiu-Ling; Yu, Chao-Hua; Gao, Fei; Qin, Su-Juan

2017-09-21

Quantum coherence and quantum correlations are important quantum resources for quantum computation and quantum information. In this paper, using entropy-based measures, we investigate the relationships between quantum correlated coherence, which is the coherence between subsystems, and two main kinds of quantum correlations as defined by quantum discord as well as quantum entanglement. In particular, we show that quantum discord and quantum entanglement can be well characterized by quantum correlated coherence. Moreover, we prove that the entanglement measure formulated by quantum correlated coherence is lower and upper bounded by the relative entropy of entanglement and the entanglement of formation, respectively, and equal to the relative entropy of entanglement for all the maximally correlated states.

Fluorescence Quantum Yield Measurements of Fluorescent Proteins: A Laboratory Experiment for a Biochemistry or Molecular Biophysics Laboratory Course

ERIC Educational Resources Information Center

Wall, Kathryn P.; Dillon, Rebecca; Knowles, Michelle K.

2015-01-01

Fluorescent proteins are commonly used in cell biology to assess where proteins are within a cell as a function of time and provide insight into intracellular protein function. However, the usefulness of a fluorescent protein depends directly on the quantum yield. The quantum yield relates the efficiency at which a fluorescent molecule converts…

Reveal quantum correlation in complementary bases

PubMed Central

Wu, Shengjun; Ma, Zhihao; Chen, Zhihua; Yu, Sixia

2014-01-01

An essential feature of genuine quantum correlation is the simultaneous existence of correlation in complementary bases. We reveal this feature of quantum correlation by defining measures based on invariance under a basis change. For a bipartite quantum state, the classical correlation is the maximal correlation present in a certain optimum basis, while the quantum correlation is characterized as a series of residual correlations in the mutually unbiased bases. Compared with other approaches to quantify quantum correlation, our approach gives information-theoretical measures that directly reflect the essential feature of quantum correlation. PMID:24503595

Acute toxicity of excess mercury on the photosynthetic performance of cyanobacterium, S. platensis--assessment by chlorophyll fluorescence analysis.

PubMed

Lu, C M; Chau, C W; Zhang, J H

2000-07-01

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.

Spectroscopy characterization and quantum yield determination of quantum dots

NASA Astrophysics Data System (ADS)

Contreras Ortiz, S. N.; Mejía Ospino, E.; Cabanzo, R.

2016-02-01

In this paper we show the characterization of two kinds of quantum dots: hydrophilic and hydrophobic, with core and core/shell respectively, using spectroscopy techniques such as UV-Vis, fluorescence and Raman. We determined the quantum yield in the quantum dots using the quinine sulphate as standard. This salt is commonly used because of its quantum yield (56%) and stability. For the CdTe excitation, we used a wavelength of 549nm and for the CdSe/ZnS excitation a wavelength of 527nm. The results show that CdSe/ZnS (49%) has better fluorescence, better quantum dots, and confirm the fluorescence result. The quantum dots have shown a good fluorescence performance, so this property will be used to replace dyes, with the advantage that quantum dots are less toxic than some dyes like the rhodamine. In addition, in this work we show different techniques to find the quantum dots emission: fluorescence spectrum, synchronous spectrum and Raman spectrum.

Optimizing inhomogeneous spin ensembles for quantum memory

NASA Astrophysics Data System (ADS)

Bensky, Guy; Petrosyan, David; Majer, Johannes; Schmiedmayer, Jörg; Kurizki, Gershon

2012-07-01

We propose a method to maximize the fidelity of quantum memory implemented by a spectrally inhomogeneous spin ensemble. The method is based on preselecting the optimal spectral portion of the ensemble by judiciously designed pulses. This leads to significant improvement of the transfer and storage of quantum information encoded in the microwave or optical field.

Contraction coefficients for noisy quantum channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiai, Fumio, E-mail: hiai.fumio@gmail.com; Ruskai, Mary Beth, E-mail: ruskai@member.ams.org

Generalized relative entropy, monotone Riemannian metrics, geodesic distance, and trace distance are all known to decrease under the action of quantum channels. We give some new bounds on, and relationships between, the maximal contraction for these quantities.

Quantum fluctuations and gapped Goldstone modes in spinor Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Beekman, Aron

2015-03-01

The classical Heisenberg ferromagnet is an exact eigenstate of the quantum Hamiltonian and therefore has no quantum fluctuations. Furthermore it has a reduced number of Goldstone modes, an order parameter that is itself a symmetry generator, is a highest-weight state for the spin algebra, and has no tower of states of vanishing energy. We derive the connection between all these properties and provide general criteria for their presence in other spontaneously-broken symmetry states. The phletora of groundstates in spinor Bose-Einstein condensates is an ideal testing ground for these predictions. In particular the phases with non-maximal polarization (e.g. the F-phase in spin-3 condensates) have an additional gapped mode that is a partner to the quadratically dispersing Goldstone mode, as compared to the maximally polarized, ferromagnetic phase. Furthermore there is a fundamental limit to the coherence time of superpositions in the non-maximally polarized state, which should manifest itself for small-size systems.

Insights from Placing Photosynthetic Light Harvesting into Context.

PubMed

Demmig-Adams, Barbara; Stewart, Jared J; Burch, Tyson A; Adams, William W

2014-08-21

Solar-energy conversion through natural photosynthesis forms the base of virtually all food chains on Earth and provides fiber, materials, and fuels, as well as inspiration for the design of biomimetic energy-conversion systems. We summarize well-known as well as recently discovered feedback loops between natural light-harvesting systems and whole-organism function in natural settings. We propose that the low effective quantum yield of natural light-harvesting systems in high light is caused by downstream limitations rather than unavoidable intrinsic vulnerabilities. We evaluate potential avenues, and their costs and benefits, for increasing the maximal rate and photon yield of photosynthesis in high light in plants and photosynthetic microbes. By summarizing mechanisms observable only in complex systems (whole plants, algae, or, in some cases, intact leaves), we aim to stimulate future research efforts on reciprocal feedback loops between light harvesting and downstream processes in whole organisms and to provide additional arguments for the significance of research on photosynthetic light harvesting.

Rigidity of quantum steering and one-sided device-independent verifiable quantum computation

NASA Astrophysics Data System (ADS)

Gheorghiu, Alexandru; Wallden, Petros; Kashefi, Elham

2017-02-01

The relationship between correlations and entanglement has played a major role in understanding quantum theory since the work of Einstein et al (1935 Phys. Rev. 47 777-80). Tsirelson proved that Bell states, shared among two parties, when measured suitably, achieve the maximum non-local correlations allowed by quantum mechanics (Cirel’son 1980 Lett. Math. Phys. 4 93-100). Conversely, Reichardt et al showed that observing the maximal correlation value over a sequence of repeated measurements, implies that the underlying quantum state is close to a tensor product of maximally entangled states and, moreover, that it is measured according to an ideal strategy (Reichardt et al 2013 Nature 496 456-60). However, this strong rigidity result comes at a high price, requiring a large number of entangled pairs to be tested. In this paper, we present a significant improvement in terms of the overhead by instead considering quantum steering where the device of the one side is trusted. We first demonstrate a robust one-sided device-independent version of self-testing, which characterises the shared state and measurement operators of two parties up to a certain bound. We show that this bound is optimal up to constant factors and we generalise the results for the most general attacks. This leads us to a rigidity theorem for maximal steering correlations. As a key application we give a one-sided device-independent protocol for verifiable delegated quantum computation, and compare it to other existing protocols, to highlight the cost of trust assumptions. Finally, we show that under reasonable assumptions, the states shared in order to run a certain type of verification protocol must be unitarily equivalent to perfect Bell states.

Deterministic entanglement distillation for secure double-server blind quantum computation.

PubMed

Sheng, Yu-Bo; Zhou, Lan

2015-01-15

Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol.

Deterministic entanglement distillation for secure double-server blind quantum computation

PubMed Central

Sheng, Yu-Bo; Zhou, Lan

2015-01-01

Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol. PMID:25588565

Accessible Information for Equally-Distant Partially-Entangled Alphabet State Resource

NASA Astrophysics Data System (ADS)

Hao, San-Ru; Hou, Bo-Yu; Xi, Xiao-Qiang; Yue, Rui-Hong

2002-02-01

We have proposed a quantum system with equally-distant partially-entangled alphabet states which has the minimal mutual overlap and the highly distinguishability, these quantum states are used as the "signal states" of the quantum communication. We have also constructed the positive operator-valued measure for these "signal states" and discussed their entanglement properties and measurement of entanglement. We calculate the accessible information for these alphabet states and show that the accessible information is closely related to the entanglement of the "signal states": the higher the entanglement of the "signal states", the better the accessible information of the quantum system, and the accessible information reaches its maximal value when the alphabet states have their maximal entanglement. The project supported in part by Foundation of the Science and Technology Committee of China, and Foundation of the Science and Technology Committee of Hunan Province of China under the contract FSTCH-21000205

Generation of maximally entangled states and coherent control in quantum dot microlenses

NASA Astrophysics Data System (ADS)

Bounouar, Samir; de la Haye, Christoph; Strauß, Max; Schnauber, Peter; Thoma, Alexander; Gschrey, Manuel; Schulze, Jan-Hindrik; Strittmatter, André; Rodt, Sven; Reitzenstein, Stephan

2018-04-01

The integration of entangled photon emitters in nanophotonic structures designed for the broadband enhancement of photon extraction is a major challenge for quantum information technologies. We study the potential of quantum dot (QD) microlenses as efficient emitters of maximally entangled photons. For this purpose, we perform quantum tomography measurements on InGaAs QDs integrated deterministically into microlenses. Even though the studied QDs show non-zero excitonic fine-structure splitting (FSS), polarization entanglement can be prepared with a fidelity close to unity. The quality of the measured entanglement is only dependent on the temporal resolution of the applied single-photon detectors compared to the period of the excitonic phase precession imposed by the FSS. Interestingly, entanglement is kept along the full excitonic wave-packet and is not affected by decoherence. Furthermore, coherent control of the upper biexcitonic state is demonstrated.

Quantum Yields of Soluble and Particulate Material in the Ocean

DTIC Science & Technology

1999-09-30

and prospects. IEEE Transactions, 46(5): 825-829 In Press Moisan, T.A. & B.G. Mitchell UV Absorption by Mycosporine - like Amino Acids in Phaeocystis...were grown to evaluate the spectral quantum yield of in vivo chlorophyll a fluorescence. We determined that mycosporine amino acids with UV absorption...evaluate the role of photoprotective pigments, including mycosporine amino acids and the xanthophyll pigments in Phaeocystis, on the spectral quantum yield

Study of a monogamous entanglement measure for three-qubit quantum systems

NASA Astrophysics Data System (ADS)

Li, Qiting; Cui, Jianlian; Wang, Shuhao; Long, Gui-Lu

2016-06-01

The entanglement quantification and classification of multipartite quantum states is an important research area in quantum information. In this paper, in terms of the reduced density matrices corresponding to all possible partitions of the entire system, a bounded entanglement measure is constructed for arbitrary-dimensional multipartite quantum states. In particular, for three-qubit quantum systems, we prove that our entanglement measure satisfies the relation of monogamy. Furthermore, we present a necessary condition for characterizing maximally entangled states using our entanglement measure.

How to make optimal use of maximal multipartite entanglement in clock synchronization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Changliang; Hofmann, Holger F.

2014-12-04

We introduce a multi-party quantum clock synchronization protocol that makes optimal use of the maximal multipartite entanglement of GHZ-type states. The measurement statistics of the protocol are analyzed and the efficiency is evaluated.

Relations between quantum correlations, purity and teleportation fidelity for the two-qubit Heisenberg XYZ system

NASA Astrophysics Data System (ADS)

Qin, Meng; Li, Yan-Biao; Wu, Fang-Ping

2014-07-01

Quantifying and understanding quantum correlations may give a direct reply for many issues regarding the interesting behaviors of quantum system. To explore the quantum correlations in quantum teleportation, we have used a two-qubit Heisenberg XYZ system with spin-orbit interaction as a quantum channel to teleport an unknown state. By using different measures and standard teleportation protocols, we have derived the analytical expressions for quantum discord, entanglement of formation, purity, and maximal teleportation fidelity of the system. We compare their different characteristics and analyze the relationships between these quantities.

Bounds on negativity for the success of quantum teleportation of qutrit-qubit system

NASA Astrophysics Data System (ADS)

K G, Paulson; Satyanarayana, S. V. M.

In the original protocol Bennet et.al., used maximally entangled pure states as quantum channel to teleport unknown states between distant observers with maximum fidelity. Noisy quantum channel can be used for imperfect teleportation. Both degree of entanglement and mixedness decide the success of teleportation in the case of mixed entangled quantum channel. . In one of our previous works, we discussed the existence of lower bound below which ,state is useless for quantum teleportation in the measure of entanglement for a fixed value of fidelity, and this lower bound decreases as rank increases for two-qubit system. We use negativity as the measure of entanglement. . In this work, we consider a qutrit-qubit system as quantum channel for teleportation, and study how the negativity and rank affect the teleportation fidelity for a class of states. We construct a new class of mixed entangled qutrit-qubit states as quantum channel, which is a convex sum of orthonormal maximally entangled and separable pure states. The classical limit of fidelity below which state is useless for quantum teleportation is fixed as 2/3. We numerically generate 30000 states and estimate the value of negativity below which each rank mixed state is useless for quantum teleportation. We also construct rank dependant boundary states by choosing appropriate eigen values, which act as upper bound for respective rank states.

[Fluorescence spectra and quantum yield of TiO2 nanocrystals synthesized by alcohothermal method].

PubMed

Song, Cui-Hong; Li, Yan-Ting; Li, Jing; Wei, Yong-Ju; Hu, Yu-Zhu; Wei, Yu

2008-01-01

Fluorescence spectra and fluorescence quantum yield of TiO2 nanocrystals were studied. Using tetra n-butyl titanate as a starting material, a facile alcohothermal technique was used to synthesize TiO2 nanocrystals. As can be seen from the transmittance electron microscopy (TEM) image, TiO2 nanocrystals with a relatively uniform particle size distribution of < 10 nm are present in the transparent sol. The transparent sol presents a strong stable fluorescence emission with a maximum at 450 nm, which is greatly dependent on the size quantization effects, defect energy level and the surface state of TiO2 nanocrystals. The quantum yield (gamma) of TiO2 was determined by the relative comparison procedure, using freshly prepared analytical purity quinine sulfate in 0.05 mol x L(-1) H2SO4 as a relative quantum yield standard. The emission quantum yield of TiO2 nanocrystals prepared in alcoholic media was calculated to be about 0.20 at wavelengths ranging from 330 to 370 nm, which was much higher than the values reported in previous works. So, it is supposed that nano-TiO2 will be applied as a potential quantum dots fluorescence probe in biological analysis.

Ensemble brightening and enhanced quantum yield in size-purified silicon nanocrystals

DOE PAGES

Miller, Joseph B.; Van Sickle, Austin R.; Anthony, Rebecca J.; ...

2012-07-18

Here, we report on the quantum yield, photoluminescence (PL) lifetime and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from themore » fractions, and we use a combination of measurement, simulation and modeling to link this ‘brightening’ to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.« less

Phase-space interference in extensive and nonextensive quantum heat engines

NASA Astrophysics Data System (ADS)

Hardal, Ali Ü. C.; Paternostro, Mauro; Müstecaplıoǧlu, Özgür E.

2018-04-01

Quantum interference is at the heart of what sets the quantum and classical worlds apart. We demonstrate that quantum interference effects involving a many-body working medium is responsible for genuinely nonclassical features in the performance of a quantum heat engine. The features with which quantum interference manifests itself in the work output of the engine depends strongly on the extensive nature of the working medium. While identifying the class of work substances that optimize the performance of the engine, our results shed light on the optimal size of such media of quantum workers to maximize the work output and efficiency of quantum energy machines.

Aeronomical determinations of the quantum yields of O (1S) and O (1D) from dissociative recombination of O2(+)

NASA Technical Reports Server (NTRS)

Yee, Jeng-Hwa; Abreu, Vincent J.; Colwell, William B.

1989-01-01

Data from the visible-airglow experiment on the Atmosphere Explorer-E satellite have been used to determine the quantum yields of O (1S) and O (1D) from the dissociative recombination of O2(+) based on a constant total recombination rate from each vibrational level. A range of values between 0.05 and 0.18 has been obtained for the quantum yield of O (1S) and shows a positive correlation with the extent of the vibrational excitation of O2(+). The quantum yield of O (1D) has been measured to be 0.9 + or - 0.2, with no apparent dependence on the vibrational distribution of O2(+).

Tuning Single Quantum Dot Emission with a Micromirror.

PubMed

Yuan, Gangcheng; Gómez, Daniel; Kirkwood, Nicholas; Mulvaney, Paul

2018-02-14

The photoluminescence of single quantum dots fluctuates between bright (on) and dark (off) states, also termed fluorescence intermittency or blinking. This blinking limits the performance of quantum dot-based devices such as light-emitting diodes and solar cells. However, the origins of the blinking remain unresolved. Here, we use a movable gold micromirror to determine both the quantum yield of the bright state and the orientation of the excited state dipole of single quantum dots. We observe that the quantum yield of the bright state is close to unity for these single QDs. Furthermore, we also study the effect of a micromirror on blinking, and then evaluate excitation efficiency, biexciton quantum yield, and detection efficiency. The mirror does not modify the off-time statistics, but it does change the density of optical states available to the quantum dot and hence the on times. The duration of the on times can be lengthened due to an increase in the radiative recombination rate.

Evidence for maximal acceleration and singularity resolution in covariant loop quantum gravity.

PubMed

Rovelli, Carlo; Vidotto, Francesca

2013-08-30

A simple argument indicates that covariant loop gravity (spin foam theory) predicts a maximal acceleration and hence forbids the development of curvature singularities. This supports the results obtained for cosmology and black holes using canonical methods.

Generating multi-photon W-like states for perfect quantum teleportation and superdense coding

NASA Astrophysics Data System (ADS)

Li, Ke; Kong, Fan-Zhen; Yang, Ming; Ozaydin, Fatih; Yang, Qing; Cao, Zhuo-Liang

2016-08-01

An interesting aspect of multipartite entanglement is that for perfect teleportation and superdense coding, not the maximally entangled W states but a special class of non-maximally entangled W-like states are required. Therefore, efficient preparation of such W-like states is of great importance in quantum communications, which has not been studied as much as the preparation of W states. In this paper, we propose a simple optical scheme for efficient preparation of large-scale polarization-based entangled W-like states by fusing two W-like states or expanding a W-like state with an ancilla photon. Our scheme can also generate large-scale W states by fusing or expanding W or even W-like states. The cost analysis shows that in generating large-scale W states, the fusion mechanism achieves a higher efficiency with non-maximally entangled W-like states than maximally entangled W states. Our scheme can also start fusion or expansion with Bell states, and it is composed of a polarization-dependent beam splitter, two polarizing beam splitters and photon detectors. Requiring no ancilla photon or controlled gate to operate, our scheme can be realized with the current photonics technology and we believe it enable advances in quantum teleportation and superdense coding in multipartite settings.

Shortcuts to adiabatic passage for the generation of a maximal Bell state and W state in an atom–cavity system

NASA Astrophysics Data System (ADS)

Lu, Mei; Chen, Qing-Qin

2018-05-01

We propose an efficient scheme to generate the maximal entangle states in an atom–cavity system between two three-level atoms in cavity quantum electronic dynamics system based on shortcuts to adiabatic passage. In the accelerate scheme, there is no need to design a time-varying coupling coefficient for the cavity. We only need to tactfully design time-dependent lasers to drive the system into the desired entangled states. Controlling the detuning between the cavity mode and lasers, we deduce a determinate analysis formula for this quantum information processing. The lasers do not need to distinguish which atom is to be affected, therefore the implementation of the experiment is simpler. The method is also generalized to generate a W state. Moreover, the accelerated program can be extended to a multi-body system and an analytical solution in a higher-dimensional system can be achieved. The influence of decoherence and variations of the parameters are discussed by numerical simulation. The results show that the maximally entangled states can be quickly prepared in a short time with high fidelity, and which are robust against both parameter fluctuations and dissipation. Our study enriches the physics and applications of multi-particle quantum entanglement preparation via shortcuts to adiabatic passage in quantum electronic dynamics.

Statistical speed of quantum states: Generalized quantum Fisher information and Schatten speed

NASA Astrophysics Data System (ADS)

Gessner, Manuel; Smerzi, Augusto

2018-02-01

We analyze families of measures for the quantum statistical speed which include as special cases the quantum Fisher information, the trace speed, i.e., the quantum statistical speed obtained from the trace distance, and more general quantifiers obtained from the family of Schatten norms. These measures quantify the statistical speed under generic quantum evolutions and are obtained by maximizing classical measures over all possible quantum measurements. We discuss general properties, optimal measurements, and upper bounds on the speed of separable states. We further provide a physical interpretation for the trace speed by linking it to an analog of the quantum Cramér-Rao bound for median-unbiased quantum phase estimation.

Solvent Dependency in the Quantum Efficiency of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] Aniline Hydrochloride.

PubMed

Pathrose, Bini; Nampoori, V P N; Radhakrishnan, P; Sahira, H; Mujeeb, A

2015-05-01

In the present work dual beam thermal lens technique is used for studying the solvent dependency on the quantum efficiency of a novel dye used for biomedical applications. The role of solvent in the absolute fluorescence quantum yield of 4-[(4-Aminophenyl)-(4-imino-1-cyclohexa-2, 5- dienylidene) methyl] aniline hydrochloride is studied using thermal lens technique. It is observed that the variation in solvents and its concentration results considerable variations in the fluorescence quantum yield. These variations are due to the non-radiative relaxation of the absorbed energy and because of the different solvent properties. The highest quantum yield of the dye is observed in the polar protic solvent-water.

In Search of the Perfect Photocage: Structure-Reactivity Relationships in meso-Methyl BODIPY Photoremovable Protecting Groups.

PubMed

Slanina, Tomáš; Shrestha, Pradeep; Palao, Eduardo; Kand, Dnyaneshwar; Peterson, Julie A; Dutton, Andrew S; Rubinstein, Naama; Weinstain, Roy; Winter, Arthur H; Klán, Petr

2017-10-25

A detailed investigation of the photophysical parameters and photochemical reactivity of meso-methyl BODIPY photoremovable protecting groups was accomplished through systematic variation of the leaving group (LG) and core substituents as well as substitutions at boron. Efficiencies of the LG release were evaluated using both steady-state and transient absorption spectroscopies as well as computational analyses to identify the optimal structural features. We find that the quantum yields for photorelease with this photocage are highly sensitive to substituent effects. In particular, we find that the quantum yields of photorelease are improved with derivatives with higher intersystem crossing quantum yields, which can be promoted by core heavy atoms. Moreover, release quantum yields are dramatically improved by boron alkylation, whereas alkylation in the meso-methyl position has no effect. Better LGs are released considerably more efficiently than poorer LGs. We find that these substituent effects are additive, for example, a 2,6-diiodo-B-dimethyl BODIPY photocage features quantum yields of 28% for the mediocre LG acetate and a 95% quantum yield of release for chloride. The high chemical and quantum yields combined with the outstanding absorption properties of BODIPY dyes lead to photocages with uncaging cross sections over 10 000 M -1 cm -1 , values that surpass cross sections of related photocages absorbing visible light. These new photocages, which absorb strongly near the second harmonic of an Nd:YAG laser (532 nm), hold promise for manipulating and interrogating biological and material systems with the high spatiotemporal control provided by pulsed laser irradiation, while avoiding the phototoxicity problems encountered with many UV-absorbing photocages. More generally, the insights gained from this structure-reactivity relationship may aid in the development of new highly efficient photoreactions.

Quantum yield measurements of light-induced H₂ generation in a photosystem I-[FeFe]-H₂ase nanoconstruct.

PubMed

Applegate, Amanda M; Lubner, Carolyn E; Knörzer, Philipp; Happe, Thomas; Golbeck, John H

2016-01-01

The quantum yield for light-induced H2 generation was measured for a previously optimized bio-hybrid cytochrome c 6-crosslinked PSI(C13G)-1,8-octanedithiol-[FeFe]-H2ase(C97G) (PSI-H2ase) nanoconstruct. The theoretical quantum yield for the PSI-H2ase nanoconstruct is 0.50 molecules of H2 per photon absorbed, which equates to a requirement of two photons per H2 generated. Illumination of the PSI-H2ase nanoconstruct with visible light between 400 and 700 nm resulted in an average quantum yield of 0.10-0.15 molecules of H2 per photon absorbed, which equates to a requirement of 6.7-10 photons per H2 generated. A possible reason for the difference between the theoretical and experimental quantum yield is the occurrence of non-productive PSI(C13G)-1,8-octanedithiol-PSIC13G (PSI-PSI) conjugates, which would absorb light without generating H2. Assuming the thiol-Fe coupling is equally efficient at producing PSI-PSI conjugates as well as in producing PSI-H2ase nanoconstructs, the theoretical quantum yield would decrease to 0.167 molecules of H2 per photon absorbed, which equates to 6 photons per H2 generated. This value is close to the range of measured values in the current study. A strategy that purifies the PSI-H2ase nanoconstructs from the unproductive PSI-PSI conjugates or that incorporates different chemistries on the PSI and [FeFe]-H2ase enzyme sites could potentially allow the PSI-H2ase nanoconstruct to approach the expected theoretical quantum yield for light-induced H2 generation.

Teleportation of quantum resources and quantum Fisher information under Unruh effect

NASA Astrophysics Data System (ADS)

Jafarzadeh, M.; Rangani Jahromi, H.; Amniat-Talab, M.

2018-07-01

Considering a pair of Unruh-DeWitt detectors, when one of them is kept inertial and the other one is accelerated and coupled to a scalar field, we address the teleportation of a two-qubit entangled state ( |ψ _in> = {cos} θ /2 |10> +e^{iφ} {sin} θ /2 |01> ) through the quantum channel created by the above system and investigate how thermal noise induced by Unruh effect affects the quantum resources and quantum Fisher information (QFI) teleportation. Our results showed while the teleported quantum resources and QFI with respect to phase parameter φ( F_{ {out}}( φ ) ) reduce with increasing acceleration and effective coupling, QFI with respect to weight parameter θ ( F_{ {out}}( θ ) ) interestingly increases after a specified value of acceleration and effective coupling. We also find that the teleported quantum resources and the precision of estimating phase parameter φ can be improved by a more entangled input state and more entangled channel. Moreover, the precision of estimating weight parameter θ increases for a maximally entangled input state only in large acceleration regime, while it does not change considerably for both maximally and partially entangled states of the channel. The influence of Unruh effect on fidelity of teleportation is also investigated. We showed that for small effective coupling the average fidelity is always larger than 2/3.

Dynamics of quantum correlation and coherence for two atoms coupled with a bath of fluctuating massless scalar field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhiming, E-mail: 465609785@qq.com; Situ, Haozhen, E-mail: situhaozhen@gmail.com

In this article, the dynamics of quantum correlation and coherence for two atoms interacting with a bath of fluctuating massless scalar field in the Minkowski vacuum is investigated. We firstly derive the master equation that describes the system evolution with initial Bell-diagonal state. Then we discuss the system evolution for three cases of different initial states: non-zero correlation separable state, maximally entangled state and zero correlation state. For non-zero correlation initial separable state, quantum correlation and coherence can be protected from vacuum fluctuations during long time evolution when the separation between the two atoms is relatively small. For maximally entangledmore » initial state, quantum correlation and coherence overall decrease with evolution time. However, for the zero correlation initial state, quantum correlation and coherence are firstly generated and then drop with evolution time; when separation is sufficiently small, they can survive from vacuum fluctuations. For three cases, quantum correlation and coherence first undergo decline and then fluctuate to relatively stable values with the increasing distance between the two atoms. Specially, for the case of zero correlation initial state, quantum correlation and coherence occur periodically revival at fixed zero points and revival amplitude declines gradually with increasing separation of two atoms.« less

Efficient quantum repeater with respect to both entanglement-concentration rate and complexity of local operations and classical communication

NASA Astrophysics Data System (ADS)

Su, Zhaofeng; Guan, Ji; Li, Lvzhou

2018-01-01

Quantum entanglement is an indispensable resource for many significant quantum information processing tasks. However, in practice, it is difficult to distribute quantum entanglement over a long distance, due to the absorption and noise in quantum channels. A solution to this challenge is a quantum repeater, which can extend the distance of entanglement distribution. In this scheme, the time consumption of classical communication and local operations takes an important place with respect to time efficiency. Motivated by this observation, we consider a basic quantum repeater scheme that focuses on not only the optimal rate of entanglement concentration but also the complexity of local operations and classical communication. First, we consider the case where two different two-qubit pure states are initially distributed in the scenario. We construct a protocol with the optimal entanglement-concentration rate and less consumption of local operations and classical communication. We also find a criterion for the projective measurements to achieve the optimal probability of creating a maximally entangled state between the two ends. Second, we consider the case in which two general pure states are prepared and general measurements are allowed. We get an upper bound on the probability for a successful measurement operation to produce a maximally entangled state without any further local operations.

Prospects and fundamental limitations of room temperature, non-avalanche, semiconductor photon-counting sensors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ma, Jiaju; Zhang, Yang; Wang, Xiaoxin; Ying, Lei; Masoodian, Saleh; Wang, Zhiyuan; Starkey, Dakota A.; Deng, Wei; Kumar, Rahul; Wu, Yang; Ghetmiri, Seyed Amir; Yu, Zongfu; Yu, Shui-Qing; Salamo, Gregory J.; Fossum, Eric R.; Liu, Jifeng

2017-05-01

This research investigates the fundamental limits and trade-space of quantum semiconductor photodetectors using the Schrödinger equation and the laws of thermodynamics.We envision that, to optimize the metrics of single photon detection, it is critical to maximize the optical absorption in the minimal volume and minimize the carrier transit process simultaneously. Integration of photon management with quantum charge transport/redistribution upon optical excitation can be engineered to maximize the quantum efficiency (QE) and data rate and minimize timing jitter at the same time. Due to the ultra-low capacitance of these quantum devices, even a single photoelectron transfer can induce a notable change in the voltage, enabling non-avalanche single photon detection at room temperature as has been recently demonstrated in Si quanta image sensors (QIS). In this research, uniform III-V quantum dots (QDs) and Si QIS are used as model systems to test the theory experimentally. Based on the fundamental understanding, we also propose proof-of-concept, photon-managed quantum capacitance photodetectors. Built upon the concepts of QIS and single electron transistor (SET), this novel device structure provides a model system to synergistically test the fundamental limits and tradespace predicted by the theory for semiconductor detectors. This project is sponsored under DARPA/ARO's DETECT Program: Fundamental Limits of Quantum Semiconductor Photodetectors.

Some applications of the most general form of the higher-order GUP with minimal length uncertainty and maximal momentum

NASA Astrophysics Data System (ADS)

Shababi, Homa; Chung, Won Sang

2018-04-01

In this paper, using the new type of D-dimensional nonperturbative Generalized Uncertainty Principle (GUP) which has predicted both a minimal length uncertainty and a maximal observable momentum,1 first, we obtain the maximally localized states and express their connections to [P. Pedram, Phys. Lett. B 714, 317 (2012)]. Then, in the context of our proposed GUP and using the generalized Schrödinger equation, we solve some important problems including particle in a box and one-dimensional hydrogen atom. Next, implying modified Bohr-Sommerfeld quantization, we obtain energy spectra of quantum harmonic oscillator and quantum bouncer. Finally, as an example, we investigate some statistical properties of a free particle, including partition function and internal energy, in the presence of the mentioned GUP.

Photogeneration of reactive transient species upon irradiation of natural water samples: Formation quantum yields in different spectral intervals, and implications for the photochemistry of surface waters.

PubMed

Marchisio, Andrea; Minella, Marco; Maurino, Valter; Minero, Claudio; Vione, Davide

2015-04-15

Chromophoric dissolved organic matter (CDOM) in surface waters is a photochemical source of several transient species such as CDOM triplet states ((3)CDOM*), singlet oxygen ((1)O2) and the hydroxyl radical (OH). By irradiation of lake water samples, it is shown here that the quantum yields for the formation of these transients by CDOM vary depending on the irradiation wavelength range, in the order UVB > UVA > blue. A possible explanation is that radiation at longer wavelengths is preferentially absorbed by the larger CDOM fractions, which show lesser photoactivity compared to smaller CDOM moieties. The quantum yield variations in different spectral ranges were definitely more marked for (3)CDOM* and OH compared to (1)O2. The decrease of the quantum yields with increasing wavelength has important implications for the photochemistry of surface waters, because long-wavelength radiation penetrates deeper in water columns compared to short-wavelength radiation. The average steady-state concentrations of the transients ((3)CDOM*, (1)O2 and OH) were modelled in water columns of different depths, based on the experimentally determined wavelength trends of the formation quantum yields. Important differences were found between such modelling results and those obtained in a wavelength-independent quantum yield scenario. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantum Yield Heterogeneity among Single Nonblinking Quantum Dots Revealed by Atomic Structure-Quantum Optics Correlation

DOE PAGES

Orfield, Noah J.; McBride, James R.; Wang, Feng; ...

2016-02-05

Physical variations in colloidal nanostructures give rise to heterogeneity in expressed optical behavior. This correlation between nanoscale structure and function demands interrogation of both atomic structure and photophysics at the level of single nanostructures to be fully understood. In this paper, by conducting detailed analyses of fine atomic structure, chemical composition, and time-resolved single-photon photoluminescence data for the same individual nanocrystals, we reveal inhomogeneity in the quantum yields of single nonblinking “giant” CdSe/CdS core/shell quantum dots (g-QDs). We find that each g-QD possesses distinctive single exciton and biexciton quantum yields that result mainly from variations in the degree of charging,more » rather than from volume or structure inhomogeneity. We further establish that there is a very limited nonemissive “dark” fraction (<2%) among the studied g-QDs and present direct evidence that the g-QD core must lack inorganic passivation for the g-QD to be “dark”. Finally and therefore, in contrast to conventional QDs, ensemble photoluminescence quantum yield is principally defined by charging processes rather than the existence of dark g-QDs.« less

Experimental tests of coherence and entanglement conservation under unitary evolutions

NASA Astrophysics Data System (ADS)

Černoch, Antonín; Bartkiewicz, Karol; Lemr, Karel; Soubusta, Jan

2018-04-01

We experimentally demonstrate the migration of coherence between composite quantum systems and their subsystems. The quantum systems are implemented using polarization states of photons in two experimental setups. The first setup is based on a linear optical controlled-phase quantum gate and the second scheme utilizes effects of nonlinear optics. Our experiment allows one to verify the relation between correlations of the subsystems and the coherence of the composite system, which was given in terms of a conservation law for maximal accessible coherence by Svozilík et al. [J. Svozilík et al., Phys. Rev. Lett. 115, 220501 (2015), 10.1103/PhysRevLett.115.220501]. We observe that the maximal accessible coherence is conserved for the implemented class of global evolutions of the composite system.

Mutually unbiased projectors and duality between lines and bases in finite quantum systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shalaby, M.; Vourdas, A., E-mail: a.vourdas@bradford.ac.uk

2013-10-15

Quantum systems with variables in the ring Z(d) are considered, and the concepts of weak mutually unbiased bases and mutually unbiased projectors are discussed. The lines through the origin in the Z(d)×Z(d) phase space, are classified into maximal lines (sets of d points), and sublines (sets of d{sub i} points where d{sub i}|d). The sublines are intersections of maximal lines. It is shown that there exists a duality between the properties of lines (resp., sublines), and the properties of weak mutually unbiased bases (resp., mutually unbiased projectors). -- Highlights: •Lines in discrete phase space. •Bases in finite quantum systems. •Dualitymore » between bases and lines. •Weak mutually unbiased bases.« less

Quantum oligopoly

NASA Astrophysics Data System (ADS)

Lo, C. F.; Kiang, D.

2003-12-01

Based upon a modification of Li et al.'s "minimal" quantization rules (Phys. Lett. A306(2002) 73), we investigate the quantum version of the Cournot and Bertrand oligopoly. In the Cournot oligopoly, the profit of each of the N firms at the Nash equilibrium point rises monotonically with the measure of the quantum entanglement. Only at maximal entanglement, however, does the Nash equilibrium point coincide with the Pareto optimal point. In the Bertrand case, the Bertrand Paradox remains for finite entanglement (i.e., the perfectly competitive stage is reached for any N>=2), whereas with maximal entanglement each of the N firms will still have a non-zero shared profit. Hence, the Bertrand Paradox is completely resolved. Furthermore, a perfectly competitive market is reached asymptotically for N → ∞ in both the Cournot and Bertrand oligopoly.

Variability in cotton fiber yield, fiber quality, and soil properties in a southeastern coastal plain

USDA-ARS?s Scientific Manuscript database

To maximize profitability, cotton (GossypiumhirsutumL.) producers must attempt to control the quality of the crop while maximizing yield. The objective of this research was to measure the intrinsic variability present in cotton fiber yield and quality. The 0.5-ha experimental site was located in a...

On quantum effects in a theory of biological evolution.

PubMed

Martin-Delgado, M A

2012-01-01

We construct a descriptive toy model that considers quantum effects on biological evolution starting from Chaitin's classical framework. There are smart evolution scenarios in which a quantum world is as favorable as classical worlds for evolution to take place. However, in more natural scenarios, the rate of evolution depends on the degree of entanglement present in quantum organisms with respect to classical organisms. If the entanglement is maximal, classical evolution turns out to be more favorable.

On Quantum Effects in a Theory of Biological Evolution

PubMed Central

Martin-Delgado, M. A.

2012-01-01

We construct a descriptive toy model that considers quantum effects on biological evolution starting from Chaitin's classical framework. There are smart evolution scenarios in which a quantum world is as favorable as classical worlds for evolution to take place. However, in more natural scenarios, the rate of evolution depends on the degree of entanglement present in quantum organisms with respect to classical organisms. If the entanglement is maximal, classical evolution turns out to be more favorable. PMID:22413059

The Broken Ring: Reduced Aromaticity in Lys-Trp Cations and High pH Tautomer Correlates with Lower Quantum Yield and Shorter Lifetimes

PubMed Central

2015-01-01

Several nonradiative processes compete with tryptophan fluorescence emission. The difficulty in spectral interpretation lies in associating specific molecular environmental features with these processes and thereby utilizing the fluorescence spectral data to identify the local environment of tryptophan. Here, spectroscopic and molecular modeling study of Lys-Trp dipeptide charged species shows that backbone-ring interactions are undistinguished. Instead, quantum mechanical ground state isosurfaces reveal variations in indole π electron distribution and density that parallel charge (as a function of pK1, pK2, and pKR) on the backbone and residues. A pattern of aromaticity-associated quantum yield and fluorescence lifetime changes emerges. Where quantum yield is high, isosurfaces have a charge distribution similar to the highest occupied molecular orbital (HOMO) of indole, which is the dominant fluorescent ground state of the 1La transition dipole moment. Where quantum yield is low, isosurface charge distribution over the ring is uneven, diminished, and even found off ring. At pH 13, the indole amine is deprotonated, and Lys-Trp quantum yield is extremely low due to tautomer structure that concentrates charge on the indole amine; the isosurface charge distribution bears scant resemblance to the indole HOMO. Such greatly diminished fluorescence has been observed for proteins where the indole nitrogen is hydrogen bonded, lending credence to the association of aromaticity changes with diminished quantum yield in proteins as well. Thus tryptophan ground state isosurfaces are an indicator of indole aromaticity, signaling the partition of excitation energy between radiative and nonradiative processes. PMID:24882092

Gaussian maximally multipartite-entangled states

NASA Astrophysics Data System (ADS)

Facchi, Paolo; Florio, Giuseppe; Lupo, Cosmo; Mancini, Stefano; Pascazio, Saverio

2009-12-01

We study maximally multipartite-entangled states in the context of Gaussian continuous variable quantum systems. By considering multimode Gaussian states with constrained energy, we show that perfect maximally multipartite-entangled states, which exhibit the maximum amount of bipartite entanglement for all bipartitions, only exist for systems containing n=2 or 3 modes. We further numerically investigate the structure of these states and their frustration for n≤7 .

Primary quantum yields of NO2 photodissociation

NASA Technical Reports Server (NTRS)

Gardner, Edward P.; Sperry, Paul D.; Calvert, Jack G.

1987-01-01

The quantum yields of formation of NO, O2, and NO2 loss are measured for NO2 vapor at low pressures (0.13-0.30 torr) irradiated at 334-405 nm wavelengths and temperature in the range 273-370 K in order to study the primary quantum efficiencies of NO2 photodecomposition. The temperature and wavelength dependences of the primary quantum efficiencies are examined. It is observed that the primary quantum efficiencies increase rapidly from near zero at 424 nm to near unity for excitation at wavelengths less than 394 nm. The theory of Pitts et al. (1964) that the energy deficiency for photodissociation of NO2 excited at wavelengths greater than 397.9 nm is due to the rotational and vibrational energy of the NO2 molecules is confirmed by the data. Values for the primary quantum yields of NO2 photodecomposition as a function of wavelength are presented.

Maximizing entanglement in bosonic Josephson junctions using shortcuts to adiabaticity and optimal control

NASA Astrophysics Data System (ADS)

Stefanatos, Dionisis; Paspalakis, Emmanuel

2018-05-01

In this article we consider a bosonic Josephson junction, a model system composed by two coupled nonlinear quantum oscillators which can be implemented in various physical contexts, initially prepared in a product of weakly populated coherent states. We quantify the maximum achievable entanglement between the modes of the junction and then use shortcuts to adiabaticity, a method developed to speed up adiabatic quantum dynamics, as well as numerical optimization, to find time-dependent controls (the nonlinearity and the coupling of the junction) which bring the system to a maximally entangled state.

Photosensitized electron transfer processes in SiO2 colloids and sodium lauryl sulfate micellar systems: Correlation of quantum yields with interfacial surface potentials

PubMed Central

Laane, Colja; Willner, Itamar; Otvos, John W.; Calvin, Melvin

1981-01-01

The effectiveness of negatively charged colloidal SiO2 particles in controlling photosensitized electron transfer reactions has been studied and compared with that of the negatively charged sodium lauryl sulfate (NaLauSO4) micellar system. In particular, the photosensitized reduction of the zwitterionic electron acceptor propylviologen sulfonate (PVS0) with tris(2,2′-bipyridinium)ruthenium(II) [Ru(bipy)32+] as the sensitizer and triethanolamine as the electron donor is found to have a quantum yield of 0.033 for formation of the radical anion (PVS[unk]) in the SiO2 colloid compared with 0.005 in the homogeneous system and 0.0086 in a NaLauSO4 micellar solution. The higher quantum yields obtained with the SiO2 colloidal system are attributed to substantial stabilization against back reaction of the intermediate photoproducts—i.e., Ru(bipy)33+ and PVS[unk]—by electrostatic repulsion of the reduced electron acceptor from the negatively charged particle surface. The binding properties of the SiO2 particles and NaLauSO4 micelles were investigated by flow dialysis. The results show that the sensitizer binds to both interfaces and that the SiO2 interface is characterized by a much higher surface potential than the micellar interface (≈-170 mV vs. -85 mV). The effect of ionic strength on the surface potential was estimated from the Gouy-Chapman theory, and the measured quantum yields of photosensitized electron transfer were correlated with surface potential at different ionic strengths. This correlation shows that the quantum yield is not affected by surface potentials smaller than ≈-40 mV. At larger potentials, the quantum yield increases rapidly. The quantum yield obtained in the micellar system at different strengths fits nicely on the correlation curve for the colloid SiO2 system. These results indicate that the surface potential is the dominant factor in the quantum yield improvement for PVS0 reduction. PMID:16593095

Generalized Entanglement Entropies of Quantum Designs.

PubMed

Liu, Zi-Wen; Lloyd, Seth; Zhu, Elton Yechao; Zhu, Huangjun

2018-03-30

The entanglement properties of random quantum states or dynamics are important to the study of a broad spectrum of disciplines of physics, ranging from quantum information to high energy and many-body physics. This Letter investigates the interplay between the degrees of entanglement and randomness in pure states and unitary channels. We reveal strong connections between designs (distributions of states or unitaries that match certain moments of the uniform Haar measure) and generalized entropies (entropic functions that depend on certain powers of the density operator), by showing that Rényi entanglement entropies averaged over designs of the same order are almost maximal. This strengthens the celebrated Page's theorem. Moreover, we find that designs of an order that is logarithmic in the dimension maximize all Rényi entanglement entropies and so are completely random in terms of the entanglement spectrum. Our results relate the behaviors of Rényi entanglement entropies to the complexity of scrambling and quantum chaos in terms of the degree of randomness, and suggest a generalization of the fast scrambling conjecture.

Generalized Entanglement Entropies of Quantum Designs

NASA Astrophysics Data System (ADS)

Liu, Zi-Wen; Lloyd, Seth; Zhu, Elton Yechao; Zhu, Huangjun

2018-03-01

The entanglement properties of random quantum states or dynamics are important to the study of a broad spectrum of disciplines of physics, ranging from quantum information to high energy and many-body physics. This Letter investigates the interplay between the degrees of entanglement and randomness in pure states and unitary channels. We reveal strong connections between designs (distributions of states or unitaries that match certain moments of the uniform Haar measure) and generalized entropies (entropic functions that depend on certain powers of the density operator), by showing that Rényi entanglement entropies averaged over designs of the same order are almost maximal. This strengthens the celebrated Page's theorem. Moreover, we find that designs of an order that is logarithmic in the dimension maximize all Rényi entanglement entropies and so are completely random in terms of the entanglement spectrum. Our results relate the behaviors of Rényi entanglement entropies to the complexity of scrambling and quantum chaos in terms of the degree of randomness, and suggest a generalization of the fast scrambling conjecture.

Electro Optical Properties of Copolymer Blends: Lasing, Electroluminescence and Photophysics

DTIC Science & Technology

2006-04-15

conjugated main chain structures with high photoluminescent and electroluminescent quantum yields. The structures incorporated fluorene containing moieties...The systems studied focused on novel conjugated main chain structures with high photoluminescent and electroluminescent quantum yields. The structures...the quantum efficient fluorine group. The properties of segmented copolymers that incorporate fluorenes were compared to the homo-PPV type systems

A versatile method for the determination of photochemical quantum yields via online UV-Vis spectroscopy.

PubMed

Stadler, Eduard; Eibel, Anna; Fast, David; Freißmuth, Hilde; Holly, Christian; Wiech, Mathias; Moszner, Norbert; Gescheidt, Georg

2018-05-16

We have developed a simple method for determining the quantum yields of photo-induced reactions. Our setup features a fibre coupled UV-Vis spectrometer, LED irradiation sources, and a calibrated spectrophotometer for precise measurements of the LED photon flux. The initial slope in time-resolved absorbance profiles provides the quantum yield. We show the feasibility of our methodology for the kinetic analysis of photochemical reactions and quantum yield determination. The typical chemical actinometers, ferrioxalate and ortho-nitrobenzaldehyde, as well as riboflavin, a spiro-compound, phosphorus- and germanium-based photoinitiators for radical polymerizations and the frequently utilized photo-switch azobenzene serve as paradigms. The excellent agreement of our results with published data demonstrates the high potential of the proposed method as a convenient alternative to the time-consuming chemical actinometry.

Fluorescence quantum yield measurements of fluorescent proteins: a laboratory experiment for a biochemistry or molecular biophysics laboratory course.

PubMed

Wall, Kathryn P; Dillon, Rebecca; Knowles, Michelle K

2015-01-01

Fluorescent proteins are commonly used in cell biology to assess where proteins are within a cell as a function of time and provide insight into intracellular protein function. However, the usefulness of a fluorescent protein depends directly on the quantum yield. The quantum yield relates the efficiency at which a fluorescent molecule converts absorbed photons into emitted photons and it is necessary to know for assessing what fluorescent protein is the most appropriate for a particular application. In this work, we have designed an upper-level, biochemistry laboratory experiment where students measure the fluorescence quantum yields of fluorescent proteins relative to a standard organic dye. Four fluorescent protein variants, enhanced cyan fluorescent protein (ECFP), enhanced green fluorescent protein (EGFP), mCitrine, and mCherry, were used, however the methods described are useful for the characterization of any fluorescent protein or could be expanded to fluorescent quantum yield measurements of organic dye molecules. The laboratory is designed as a guided inquiry project and takes two, 4 hr laboratory periods. During the first day students design the experiment by selecting the excitation wavelength, choosing the standard, and determining the concentration needed for the quantum yield experiment that takes place in the second laboratory period. Overall, this laboratory provides students with a guided inquiry learning experience and introduces concepts of fluorescence biophysics into a biochemistry laboratory curriculum. © 2014 The International Union of Biochemistry and Molecular Biology.

Photochemical redox reactions of copper(II)-alanine complexes in aqueous solutions.

PubMed

Lin, Chen-Jui; Hsu, Chao-Sheng; Wang, Po-Yen; Lin, Yi-Liang; Lo, Yu-Shiu; Wu, Chien-Hou

2014-05-19

The photochemical redox reactions of Cu(II)/alanine complexes have been studied in deaerated solutions over an extensive range of pH, Cu(II) concentration, and alanine concentration. Under irradiation, the ligand-to-metal charge transfer results in the reduction of Cu(II) to Cu(I) and the concomitant oxidation of alanine, which produces ammonia and acetaldehyde. Molar absorptivities and quantum yields of photoproducts for Cu(II)/alanine complexes at 313 nm are characterized mainly with the equilibrium Cu(II) speciation where the presence of simultaneously existing Cu(II) species is taken into account. By applying regression analysis, individual Cu(I) quantum yields are determined to be 0.094 ± 0.014 for the 1:1 complex (CuL) and 0.064 ± 0.012 for the 1:2 complex (CuL2). Individual quantum yields of ammonia are 0.055 ± 0.007 for CuL and 0.036 ± 0.005 for CuL2. Individual quantum yields of acetaldehyde are 0.030 ± 0.007 for CuL and 0.024 ± 0.007 for CuL2. CuL always has larger quantum yields than CuL2, which can be attributed to the Cu(II) stabilizing effect of the second ligand. For both CuL and CuL2, the individual quantum yields of Cu(I), ammonia, and acetaldehyde are in the ratio of 1.8:1:0.7. A reaction mechanism for the formation of the observed photoproducts is proposed.

Generalized teleportation by quantum walks

NASA Astrophysics Data System (ADS)

Wang, Yu; Shang, Yun; Xue, Peng

2017-09-01

We develop a generalized teleportation scheme based on quantum walks with two coins. For an unknown qubit state, we use two-step quantum walks on the line and quantum walks on the cycle with four vertices for teleportation. For any d-dimensional states, quantum walks on complete graphs and quantum walks on d-regular graphs can be used for implementing teleportation. Compared with existing d-dimensional states teleportation, prior entangled state is not required and the necessary maximal entanglement resource is generated by the first step of quantum walk. Moreover, two projective measurements with d elements are needed by quantum walks on the complete graph, rather than one joint measurement with d^2 basis states. Quantum walks have many applications in quantum computation and quantum simulations. This is the first scheme of realizing communicating protocol with quantum walks, thus opening wider applications.

Generalized model screening potentials for Fermi-Dirac plasmas

NASA Astrophysics Data System (ADS)

Akbari-Moghanjoughi, M.

2016-04-01

In this paper, some properties of relativistically degenerate quantum plasmas, such as static ion screening, structure factor, and Thomson scattering cross-section, are studied in the framework of linearized quantum hydrodynamic theory with the newly proposed kinetic γ-correction to Bohm term in low frequency limit. It is found that the correction has a significant effect on the properties of quantum plasmas in all density regimes, ranging from solid-density up to that of white dwarf stars. It is also found that Shukla-Eliasson attractive force exists up to a few times the density of metals, and the ionic correlations are seemingly apparent in the radial distribution function signature. Simplified statically screened attractive and repulsive potentials are presented for zero-temperature Fermi-Dirac plasmas, valid for a wide range of quantum plasma number-density and atomic number values. Moreover, it is observed that crystallization of white dwarfs beyond a critical core number-density persists with this new kinetic correction, but it is shifted to a much higher number-density value of n0 ≃ 1.94 × 1037 cm-3 (1.77 × 1010 gr cm-3), which is nearly four orders of magnitude less than the nuclear density. It is found that the maximal Thomson scattering with the γ-corrected structure factor is a remarkable property of white dwarf stars. However, with the new γ-correction, the maximal scattering shifts to the spectrum region between hard X-ray and low-energy gamma-rays. White dwarfs composed of higher atomic-number ions are observed to maximally Thomson-scatter at slightly higher wavelengths, i.e., they maximally scatter slightly low-energy photons in the presence of correction.

Polariton-Assisted Singlet Fission in Acene Aggregates.

PubMed

Martínez-Martínez, Luis A; Du, Matthew; F Ribeiro, Raphael; Kéna-Cohen, Stéphane; Yuen-Zhou, Joel

2018-04-19

Singlet fission is an important candidate to increase energy conversion efficiency in organic photovoltaics by providing a pathway to increase the quantum yield of excitons per photon absorbed in select materials. We investigate the dependence of exciton quantum yield for acenes in the strong light-matter interaction (polariton) regime, where the materials are embedded in optical microcavities. Starting from an open-quantum-systems approach, we build a kinetic model for time-evolution of species of interest in the presence of singlet quenchers and show that polaritons can decrease or increase exciton quantum yields compared to the cavity-free case. In particular, we find that hexacene, under the conditions of our model, can feature a higher yield than cavity-free pentacene when assisted by polaritonic effects. Similarly, we show that pentacene yield can be increased when assisted by polariton states. Finally, we address how various relaxation processes between bright and dark states in lossy microcavities affect polariton photochemistry. Our results also provide insights on how to choose microcavities to enhance similarly related chemical processes.

Light propagation and fluorescence quantum yields in liquid scintillators

NASA Astrophysics Data System (ADS)

Buck, C.; Gramlich, B.; Wagner, S.

2015-09-01

For the simulation of the scintillation and Cherenkov light propagation in large liquid scintillator detectors a detailed knowledge about the absorption and emission spectra of the scintillator molecules is mandatory. Furthermore reemission probabilities and quantum yields of the scintillator components influence the light propagation inside the liquid. Absorption and emission properties are presented for liquid scintillators using 2,5-Diphenyloxazole (PPO) and 4-bis-(2-Methylstyryl)benzene (bis-MSB) as primary and secondary wavelength shifter. New measurements of the quantum yields for various aromatic molecules are shown.

Potential advantages of curve sawing non-straight hardwood logs

Treesearch

Philip A. Araman

2007-01-01

Curve sawing is not new to the softwood industry. Softwood sawmill managers think about how fast they can push logs through their sawmill to maximize the yield of 1x and 2x lumber. Curve sawing helps mills maximize yield when sawing non-straight logs. Hardwood sawmill managers don’t want to push logs through their sawmills, because they want to maximize lumber value...

Quantum mechanics: The Bayesian theory generalized to the space of Hermitian matrices

NASA Astrophysics Data System (ADS)

Benavoli, Alessio; Facchini, Alessandro; Zaffalon, Marco

2016-10-01

We consider the problem of gambling on a quantum experiment and enforce rational behavior by a few rules. These rules yield, in the classical case, the Bayesian theory of probability via duality theorems. In our quantum setting, they yield the Bayesian theory generalized to the space of Hermitian matrices. This very theory is quantum mechanics: in fact, we derive all its four postulates from the generalized Bayesian theory. This implies that quantum mechanics is self-consistent. It also leads us to reinterpret the main operations in quantum mechanics as probability rules: Bayes' rule (measurement), marginalization (partial tracing), independence (tensor product). To say it with a slogan, we obtain that quantum mechanics is the Bayesian theory in the complex numbers.

Intermediate quantum maps for quantum computation

NASA Astrophysics Data System (ADS)

Giraud, O.; Georgeot, B.

2005-10-01

We study quantum maps displaying spectral statistics intermediate between Poisson and Wigner-Dyson. It is shown that they can be simulated on a quantum computer with a small number of gates, and efficiently yield information about fidelity decay or spectral statistics. We study their matrix elements and entanglement production and show that they converge with time to distributions which differ from random matrix predictions. A randomized version of these maps can be implemented even more economically and yields pseudorandom operators with original properties, enabling, for example, one to produce fractal random vectors. These algorithms are within reach of present-day quantum computers.

Quantum Yields of CAM Plants Measured by Photosynthetic O2 Exchange 1

PubMed Central

Adams, William W.; Nishida, Kojiro; Osmond, C. Barry

1986-01-01

The quantum yield of photosynthetic O2 exchange was measured in eight species of leaf succulents representative of both malic enzyme type and phosphoenolpyruvate carboxykinase type CAM plants. Measurements were made at 25°C and CO2 saturation using a leaf disc O2 electrode system, either during or after deacidification. The mean quantum yield was 0.095 ± 0.012 (sd) moles O2 per mole quanta, which compared with 0.094 ± 0.006 (sd) moles O2 per mole quanta for spinach leaf discs measured under the same conditions. There were no consistent differences in quantum yield between decarboxylation types or during different phases of CAM metabolism. On the basis of current notions of compartmentation of CAM biochemistry, our observations are interpreted to indicate that CO2 refixation is energetically independent of gluconeogenesis during deacidification. PMID:16664793

Maximizing plant density affects broccoli yield and quality

USDA-ARS?s Scientific Manuscript database

Increased demand for fresh market bunch broccoli (Brassica oleracea L. var. italica) has led to increased production along the United States east coast. Maximizing broccoli yields is a primary concern for quickly expanding southeastern commercial markets. This broccoli plant density study was carr...

Photodynamic Efficiency: From Molecular Photochemistry to Cell Death

PubMed Central

Bacellar, Isabel O. L.; Tsubone, Tayana M.; Pavani, Christiane; Baptista, Mauricio S.

2015-01-01

Photodynamic therapy (PDT) is a clinical modality used to treat cancer and infectious diseases. The main agent is the photosensitizer (PS), which is excited by light and converted to a triplet excited state. This latter species leads to the formation of singlet oxygen and radicals that oxidize biomolecules. The main motivation for this review is to suggest alternatives for achieving high-efficiency PDT protocols, by taking advantage of knowledge on the chemical and biological processes taking place during and after photosensitization. We defend that in order to obtain specific mechanisms of cell death and maximize PDT efficiency, PSes should oxidize specific molecular targets. We consider the role of subcellular localization, how PS photochemistry and photophysics can change according to its nanoenvironment, and how can all these trigger specific cell death mechanisms. We propose that in order to develop PSes that will cause a breakthrough enhancement in the efficiency of PDT, researchers should first consider tissue and intracellular localization, instead of trying to maximize singlet oxygen quantum yields in in vitro tests. In addition to this, we also indicate many open questions and challenges remaining in this field, hoping to encourage future research. PMID:26334268

Tight-binding calculation of single-band and generalized Wannier functions of graphene

NASA Astrophysics Data System (ADS)

Ribeiro, Allan Victor; Bruno-Alfonso, Alexys

Recent work has shown that a tight-binding approach associated with Wannier functions (WFs) provides an intuitive physical image of the electronic structure of graphene. Regarding the case of graphene, Marzari et al. displayed the calculated WFs and presented a comparison between the Wannier-interpolated bands and the bands generated by using the density-functional code. Jung and MacDonald provided a tight-binding model for the π-bands of graphene that involves maximally localized Wannier functions (MLWFs). The mixing of the bands yields better localized WFs. In the present work, the MLWFs of graphene are calculated by combining the Quantum-ESPRESSO code and tight-binding approach. The MLWFs of graphene are calculated from the Bloch functions obtained through a tight binding approach that includes interactions and overlapping obtained by partially fitting the DFT bands. The phase of the Bloch functions of each band is appropriately chosen to produce MLWFs. The same thing applies to the coefficients of their linear combination in the generalized case. The method allows for an intuitive understanding of the maximally localized WFs of graphene and shows excellent agreement with the literature. Moreover, it provides accurate results at reduced computational cost.

Two-step entanglement concentration for arbitrary electronic cluster state

NASA Astrophysics Data System (ADS)

Zhao, Sheng-Yang; Liu, Jiong; Zhou, Lan; Sheng, Yu-Bo

2013-12-01

We present an efficient protocol for concentrating an arbitrary four-electron less-entangled cluster state into a maximally entangled cluster state. As a two-step entanglement concentration protocol (ECP), it only needs one pair of less-entangled cluster state, which makes this ECP more economical. With the help of electronic polarization beam splitter (PBS) and the charge detection, the whole concentration process is essentially the quantum nondemolition (QND) measurement. Therefore, the concentrated maximally entangled state can be remained for further application. Moreover, the discarded terms in some traditional ECPs can be reused to obtain a high success probability. It is feasible and useful in current one-way quantum computation.

Absolute continuity for operator valued completely positive maps on C∗-algebras

NASA Astrophysics Data System (ADS)

Gheondea, Aurelian; Kavruk, Ali Şamil

2009-02-01

Motivated by applicability to quantum operations, quantum information, and quantum probability, we investigate the notion of absolute continuity for operator valued completely positive maps on C∗-algebras, previously introduced by Parthasarathy [in Athens Conference on Applied Probability and Time Series Analysis I (Springer-Verlag, Berlin, 1996), pp. 34-54]. We obtain an intrinsic definition of absolute continuity, we show that the Lebesgue decomposition defined by Parthasarathy is the maximal one among all other Lebesgue-type decompositions and that this maximal Lebesgue decomposition does not depend on the jointly dominating completely positive map, we obtain more flexible formulas for calculating the maximal Lebesgue decomposition, and we point out the nonuniqueness of the Lebesgue decomposition as well as a sufficient condition for uniqueness. In addition, we consider Radon-Nikodym derivatives for absolutely continuous completely positive maps that, in general, are unbounded positive self-adjoint operators affiliated to a certain von Neumann algebra, and we obtain a spectral approximation by bounded Radon-Nikodym derivatives. An application to the existence of the infimum of two completely positive maps is indicated, and formulas in terms of Choi's matrices for the Lebesgue decomposition of completely positive maps in matrix algebras are obtained.

Poly(vinylpyrrolidone) supported copper nanoclusters: glutathione enhanced blue photoluminescence for application in phosphor converted light emitting devices

NASA Astrophysics Data System (ADS)

Wang, Zhenguang; Susha, Andrei S.; Chen, Bingkun; Reckmeier, Claas; Tomanec, Ondrej; Zboril, Radek; Zhong, Haizheng; Rogach, Andrey L.

2016-03-01

Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92.Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92. Electronic supplementary information (ESI) available: The optical spectra of control experiments for Cu NC synthesis, optimization of the reaction conditions, and spectra for LEDs chips and blue LEDs. See DOI: 10.1039/c6nr00806b

Single-particle tracking of quantum dot-conjugated prion proteins inside yeast cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuji, Toshikazu; Kawai-Noma, Shigeko; Pack, Chan-Gi

2011-02-25

Research highlights: {yields} We develop a method to track a quantum dot-conjugated protein in yeast cells. {yields} We incorporate the conjugated quantum dot proteins into yeast spheroplasts. {yields} We track the motions by conventional or 3D tracking microscopy. -- Abstract: Yeast is a model eukaryote with a variety of biological resources. Here we developed a method to track a quantum dot (QD)-conjugated protein in the budding yeast Saccharomyces cerevisiae. We chemically conjugated QDs with the yeast prion Sup35, incorporated them into yeast spheroplasts, and tracked the motions by conventional two-dimensional or three-dimensional tracking microscopy. The method paves the way towardmore » the individual tracking of proteins of interest inside living yeast cells.« less

Quantum Teamwork for Unconditional Multiparty Communication with Gaussian States

NASA Astrophysics Data System (ADS)

Zhang, Jing; Adesso, Gerardo; Xie, Changde; Peng, Kunchi

2009-08-01

We demonstrate the capability of continuous variable Gaussian states to communicate multipartite quantum information. A quantum teamwork protocol is presented according to which an arbitrary possibly entangled multimode state can be faithfully teleported between two teams each comprising many cooperative users. We prove that N-mode Gaussian weighted graph states exist for arbitrary N that enable unconditional quantum teamwork implementations for any arrangement of the teams. These perfect continuous variable maximally multipartite entangled resources are typical among pure Gaussian states and are unaffected by the entanglement frustration occurring in multiqubit states.

Optimal GHZ Paradox for Three Qubits

NASA Astrophysics Data System (ADS)

Ren, Changliang; Su, Hong-Yi; Xu, Zhen-Peng; Wu, Chunfeng; Chen, Jing-Ling

2015-08-01

Quatum nonlocality as a valuable resource is of vital importance in quantum information processing. The characterization of the resource has been extensively investigated mainly for pure states, while relatively less is know for mixed states. Here we prove the existence of the optimal GHZ paradox by using a novel and simple method to extract an optimal state that can saturate the tradeoff relation between quantum nonlocality and the state purity. In this paradox, the logical inequality which is formulated by the GHZ-typed event probabilities can be violated maximally by the optimal state for any fixed amount of purity (or mixedness). Moreover, the optimal state can be described as a standard GHZ state suffering flipped color noise. The maximal amount of noise that the optimal state can resist is 50%. We suggest our result to be a step toward deeper understanding of the role played by the AVN proof of quantum nonlocality as a useful physical resource.

Single-copy entanglement in critical quantum spin chains

NASA Astrophysics Data System (ADS)

Eisert, J.; Cramer, M.

2005-10-01

We consider the single-copy entanglement as a quantity to assess quantum correlations in the ground state in quantum many-body systems. We show for a large class of models that already on the level of single specimens of spin chains, criticality is accompanied with the possibility of distilling a maximally entangled state of arbitrary dimension from a sufficiently large block deterministically, with local operations and classical communication. These analytical results—which refine previous results on the divergence of block entropy as the rate at which maximally entangled pairs can be distilled from many identically prepared chains—are made quantitative for general isotropic translationally invariant spin chains that can be mapped onto a quasifree fermionic system, and for the anisotropic XY model. For the XX model, we provide the asymptotic scaling of ˜(1/6)log2(L) , and contrast it with the block entropy.

Self-guided method to search maximal Bell violations for unknown quantum states

NASA Astrophysics Data System (ADS)

Yang, Li-Kai; Chen, Geng; Zhang, Wen-Hao; Peng, Xing-Xiang; Yu, Shang; Ye, Xiang-Jun; Li, Chuan-Feng; Guo, Guang-Can

2017-11-01

In recent decades, a great variety of research and applications concerning Bell nonlocality have been developed with the advent of quantum information science. Providing that Bell nonlocality can be revealed by the violation of a family of Bell inequalities, finding maximal Bell violation (MBV) for unknown quantum states becomes an important and inevitable task during Bell experiments. In this paper we introduce a self-guided method to find MBVs for unknown states using a stochastic gradient ascent algorithm (SGA), by parametrizing the corresponding Bell operators. For three investigated systems (two qubit, three qubit, and two qutrit), this method can ascertain the MBV of general two-setting inequalities within 100 iterations. Furthermore, we prove SGA is also feasible when facing more complex Bell scenarios, e.g., d -setting d -outcome Bell inequality. Moreover, compared to other possible methods, SGA exhibits significant superiority in efficiency, robustness, and versatility.

Highly efficient hyperentanglement concentration with two steps assisted by quantum swap gates.

PubMed

Ren, Bao-Cang; Long, Gui Lu

2015-11-10

We present a two-step hyperentanglement concentration protocol (hyper-ECP) for polarization-spatial hyperentangled Bell states based on the high-capacity character of hyperentanglement resorting to the swap gates, which is used to obtain maximally hyperentangled states from partially hyperentangled pure states in long-distance quantum communication. The swap gate, which is constructed with the giant optical circular birefringence (GOCB) of a diamond nitrogen-vacancy (NV) center embedded in a photonic crystal cavity, can be used to transfer the information in one degree of freedom (DOF) between photon systems. By transferring the useful information between hyperentangled photon pairs, more photon pairs in maximally hyperentangled state can be obtained in our hyper-ECP, and the success probability of the hyper-ECP is greatly improved. Moreover, we show that the high-fidelity quantum gate operations can be achieved by mapping the infidelities to heralded losses even in the weak coupling regime.

Divergence-free approach for obtaining decompositions of quantum-optical processes

NASA Astrophysics Data System (ADS)

Sabapathy, K. K.; Ivan, J. S.; García-Patrón, R.; Simon, R.

2018-02-01

Operator-sum representations of quantum channels can be obtained by applying the channel to one subsystem of a maximally entangled state and deploying the channel-state isomorphism. However, for continuous-variable systems, such schemes contain natural divergences since the maximally entangled state is ill defined. We introduce a method that avoids such divergences by utilizing finitely entangled (squeezed) states and then taking the limit of arbitrary large squeezing. Using this method, we derive an operator-sum representation for all single-mode bosonic Gaussian channels where a unique feature is that both quantum-limited and noisy channels are treated on an equal footing. This technique facilitates a proof that the rank-1 Kraus decomposition for Gaussian channels at its respective entanglement-breaking thresholds, obtained in the overcomplete coherent-state basis, is unique. The methods could have applications to simulation of continuous-variable channels.

Highly efficient hyperentanglement concentration with two steps assisted by quantum swap gates

PubMed Central

Ren, Bao-Cang; Long, Gui Lu

2015-01-01

We present a two-step hyperentanglement concentration protocol (hyper-ECP) for polarization-spatial hyperentangled Bell states based on the high-capacity character of hyperentanglement resorting to the swap gates, which is used to obtain maximally hyperentangled states from partially hyperentangled pure states in long-distance quantum communication. The swap gate, which is constructed with the giant optical circular birefringence (GOCB) of a diamond nitrogen-vacancy (NV) center embedded in a photonic crystal cavity, can be used to transfer the information in one degree of freedom (DOF) between photon systems. By transferring the useful information between hyperentangled photon pairs, more photon pairs in maximally hyperentangled state can be obtained in our hyper-ECP, and the success probability of the hyper-ECP is greatly improved. Moreover, we show that the high-fidelity quantum gate operations can be achieved by mapping the infidelities to heralded losses even in the weak coupling regime. PMID:26552898

Topological Quantum Buses: Coherent Quantum Information Transfer between Topological and Conventional Qubits

NASA Astrophysics Data System (ADS)

Bonderson, Parsa; Lutchyn, Roman M.

2011-04-01

We propose computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits. We describe a concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit. Specifically, this device measures the joint (fermion) parity of these two different qubits by using the Aharonov-Casher effect in conjunction with an ancilliary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows one to produce states in which the topological and conventional qubits are maximally entangled and to teleport quantum states between the topological and conventional quantum systems.

Work extremum principle: structure and function of quantum heat engines.

PubMed

Allahverdyan, Armen E; Johal, Ramandeep S; Mahler, Guenter

2008-04-01

We consider a class of quantum heat engines consisting of two subsystems interacting with a work-source and coupled to two separate baths at different temperatures Th>Tc. The purpose of the engine is to extract work due to the temperature difference. Its dynamics is not restricted to the near equilibrium regime. The engine structure is determined by maximizing the extracted work under various constraints. When this maximization is carried out at finite power, the engine dynamics is described by well-defined temperatures and satisfies the local version of the second law. In addition, its efficiency is bounded from below by the Curzon-Ahlborn value 1-radical Tc/Th and from above by the Carnot value 1-(Tc/Th). The latter is reached-at finite power--for a macroscopic engine, while the former is achieved in the equilibrium limit Th-->Tc . The efficiency that maximizes the power is strictly larger than the Curzon-Ahloborn value. When the work is maximized at a zero power, even a small (few-level) engine extracts work right at the Carnot efficiency.

Automated error correction in IBM quantum computer and explicit generalization

NASA Astrophysics Data System (ADS)

Ghosh, Debjit; Agarwal, Pratik; Pandey, Pratyush; Behera, Bikash K.; Panigrahi, Prasanta K.

2018-06-01

Construction of a fault-tolerant quantum computer remains a challenging problem due to unavoidable noise and fragile quantum states. However, this goal can be achieved by introducing quantum error-correcting codes. Here, we experimentally realize an automated error correction code and demonstrate the nondestructive discrimination of GHZ states in IBM 5-qubit quantum computer. After performing quantum state tomography, we obtain the experimental results with a high fidelity. Finally, we generalize the investigated code for maximally entangled n-qudit case, which could both detect and automatically correct any arbitrary phase-change error, or any phase-flip error, or any bit-flip error, or combined error of all types of error.

Photoelectric Effect: Back to Basics.

ERIC Educational Resources Information Center

Powell, R. A.

1978-01-01

Presents a simplified theoretical analysis of the variation of quantum yield with photon energy in the photoelectric experiment. Describes a way to amplify the experiment and make it more instructive to advanced students through the measurement of quantum yield of a photo cell. (GA)

DETERMINATION OF APPARENT QUANTUM YIELD SPECTRA FOR THE FORMATION OF BIOLOGICALLY LABILE PHOTOPRODUCTS

EPA Science Inventory

Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, a...

Terahertz cascades from nanoparticles

NASA Astrophysics Data System (ADS)

Arnardottir, K. B.; Liew, T. C. H.

2018-05-01

In this article we propose a system capable of terahertz (THz) radiation with quantum yield above unity. The system consists of nanoparticles where the material composition varies along the radial direction of each nanoparticle in such a way that a ladder of equidistant energy levels emerges. By then exciting the highest level of this ladder we produce multiple photons of the same frequency in the THz range. We demonstrate how we can calculate a continuous material composition profile that achieves a high quantum yield and then show that a more experimentally friendly design of a multishell nanoparticle can still result in a high quantum yield.

Photo-kinetics of photoinduced transformation reaction of methylene green with titanium trichloride in different solvents

NASA Astrophysics Data System (ADS)

Nadeem, Syed Muhammad Saqib; Saeed, Rehana

2017-08-01

The photo-kinetics of photoinduced transformation reaction of methylene green and titanium trichloride was investigated in water and different aqueous-alcoholic solvents. The reaction is pseudo-first order, dependent only on the concentration of titanium trichloride at fixed concentration of methylene green. The effect of water and aqueous-alcoholic solvents was studied in the acidic range from 4 to 7. It was observed that the quantum yield (φ) of reaction increased with increase in polarity of the solvent. The quantum yield (φ) was high in acidic condition and decreased with further increase in acidity. The quantum yield (φ) increased sharply with increase in concentration of titanium trichloride while it almost remained unaffected by change in concentration of methylene green. The addition of ions increased the quantum yield (φ) of reaction. The increase in temperature decreased the rate and quantum yield (φ) of reaction. An electron transfer mechanism for the reaction has been proposed in accordance with the kinetics of reaction. The absence of any reaction intermediate was confirmed by spectroscopic investigations. Activation energy ( E a) was calculated by Arrhenius relation. Thermodynamic parameters such as activation energy ( E a), enthalpy change (Δ H), free energy change (Δ G) and entropy change (Δ S) were also evaluated.

Fluorescence quantum yield of carbon dioxide for quantitative UV laser-induced fluorescence in high-pressure flames

NASA Astrophysics Data System (ADS)

Lee, T.; Bessler, W. G.; Yoo, J.; Schulz, C.; Jeffries, J. B.; Hanson, R. K.

2008-11-01

The fluorescence quantum yield for ultraviolet laser-induced fluorescence of CO2 is determined for selected excitation wavelengths in the range 215-250 nm. Wavelength-resolved laser-induced fluorescence (LIF) spectra of CO2, NO, and O2 are measured in the burned gases of a laminar CH4/air flame ( φ=0.9 and 1.1) at 20 bar with additional NO seeded into the flow. The fluorescence spectra are fit to determine the relative contribution of the three species to infer an estimate of fluorescence quantum yield for CO2 that ranges from 2-8×10-6 depending on temperature and excitation wavelength with an estimated uncertainty of ±0.5×10-6. The CO2 fluorescence signal increases linearly with gas pressure for flames with constant CO2 mole fraction for the 10 to 60 bar range, indicating that collisional quenching is not an important contributor to the CO2 fluorescence quantum yield. Spectral simulation calculations are used to choose two wavelengths for excitation of CO2, 239.34 and 242.14 nm, which minimize interference from LIF of NO and O2. Quantitative LIF images of CO2 are demonstrated using these two excitation wavelengths and the measured fluorescence quantum yield.

Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Ke; Verschuuren, Marc A.; Lozano, Gabriel

2015-08-21

Optical losses in metals represent the largest limitation to the external quantum yield of emitters coupled to plasmonic antennas. These losses can be at the emission wavelength, but they can be more important at shorter wavelengths, i.e., at the excitation wavelength of the emitters, where the conductivity of metals is usually lower. We present accurate measurements of the absolute external photoluminescent quantum yield of a thin layer of emitting material deposited over a periodic nanoantenna phased array. Emission and absorptance measurements of the sample are performed using a custom-made setup including an integrating sphere and variable angle excitation. The measurementsmore » reveal a strong dependence of the external quantum yield on the angle at which the optical field excites the sample. Such behavior is attributed to the coupling between far-field illumination and near-field excitation mediated by the collective resonances supported by the array. Numerical simulations confirm that the inherent losses associated with the metal can be greatly reduced by selecting an optimum angle of illumination, which boosts the light conversion efficiency in the emitting layer. This combined experimental and numerical characterization of the emission from plasmonic arrays reveals the need to carefully design the illumination to achieve the maximum external quantum yield.« less

The limits of crop productivity: validating theoretical estimates and determining the factors that limit crop yields in optimal environments

NASA Technical Reports Server (NTRS)

Bugbee, B.; Monje, O.

1992-01-01

Plant scientists have sought to maximize the yield of food crops since the beginning of agriculture. There are numerous reports of record food and biomass yields (per unit area) in all major crop plants, but many of the record yield reports are in error because they exceed the maximal theoretical rates of the component processes. In this article, we review the component processes that govern yield limits and describe how each process can be individually measured. This procedure has helped us validate theoretical estimates and determine what factors limit yields in optimal environments.

Multipartite quantum correlations among atoms in QED cavities

NASA Astrophysics Data System (ADS)

Batle, J.; Farouk, A.; Tarawneh, O.; Abdalla, S.

2018-02-01

We study the nonlocality dynamics for two models of atoms in cavity quantum electrodynamics (QED); the first model contains atoms in a single cavity undergoing nearest-neighbor interactions with no initial correlation, and the second contains atoms confined in n different and noninteracting cavities, all of which were initially prepared in a maximally correlated state of n qubits corresponding to the atomic degrees of freedom. The nonlocality evolution of the states in the second model shows that the corresponding maximal violation of a multipartite Bell inequality exhibits revivals at precise times, defining, nonlocality sudden deaths and nonlocality sudden rebirths, in analogy with entanglement. These quantum correlations are provided analytically for the second model to make the study more thorough. Differences in the first model regarding whether the array of atoms inside the cavity is arranged in a periodic or open fashion are crucial to the generation or redistribution of quantum correlations. This contribution paves the way to using the nonlocality multipartite correlation measure for describing the collective complex behavior displayed by slightly interacting cavity QED arrays.

Efficient Carrier Multiplication in Colloidal Silicon Nanorods

DOE PAGES

Stolle, Carl Jackson; Lu, Xiaotang; Yu, Yixuan; ...

2017-08-01

In this study, auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimesmore » increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy E g. Beyond a critical length, the CM quantum yield decreases. Finally, nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2.9E g, which corresponded to a multiexciton yield that was twice as high as observed for the spherical nanocrystals.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stolle, Carl Jackson; Lu, Xiaotang; Yu, Yixuan

In this study, auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimesmore » increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy E g. Beyond a critical length, the CM quantum yield decreases. Finally, nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2.9E g, which corresponded to a multiexciton yield that was twice as high as observed for the spherical nanocrystals.« less

Effects of Controlled-Release Fertilizer on Leaf Area Index and Fruit Yield in High-Density Soilless Tomato Culture Using Low Node-Order Pinching

PubMed Central

Kinoshita, Takafumi; Yano, Takayoshi; Sugiura, Makoto; Nagasaki, Yuji

2014-01-01

To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m2·m−2; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method. PMID:25402478

Effects of Bleaching by Nitrogen Deficiency on the Quantum Yield of Photosystem II in Synechocystis sp. PCC 6803 Revealed by Chl Fluorescence Measurements.

PubMed

Ogawa, Takako; Sonoike, Kintake

2016-03-01

Estimation of photosynthesis by Chl fluorescence measurement of cyanobacteria is always problematic due to the interference from respiratory electron transfer and from phycocyanin fluorescence. The interference from respiratory electron transfer could be avoided by the use of DCMU or background illumination by blue light, which oxidizes the plastoquinone pool that tends to be reduced by respiration. On the other hand, the precise estimation of photosynthesis in cells with a different phycobilisome content by Chl fluorescence measurement is difficult. By subtracting the basal fluorescence due to the phycobilisome and PSI, it becomes possible to estimate the precise maximum quantum yield of PSII in cyanobacteria. Estimated basal fluorescence accounted for 60% of the minimum fluorescence, resulting in a large difference between the 'apparent' yield and 'true' yield under high phycocyanin conditions. The calculated value of the 'true' maximum quantum yield of PSII was around 0.8, which was similar to the value observed in land plants. The results suggest that the cause of the apparent low yield reported in cyanobacteria is mainly ascribed to the interference from phycocyanin fluorescence. We also found that the 'true' maximum quantum yield of PSII decreased under nitrogen-deficient conditions, suggesting the impairment of the PSII reaction center, while the 'apparent' maximum quantum yield showed a marginal change under the same conditions. Due to the high contribution of phycocyanin fluorescence in cyanobacteria, it is essential to eliminate the influence of the change in phycocyanin content on Chl fluorescence measurement and to evaluate the 'true' photosynthetic condition. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Universal Three-Qubit Entanglement Generation Based on Linear Optical Elements and Quantum Non-Demolition Detectors

NASA Astrophysics Data System (ADS)

Liu, Xin-Chang

2017-02-01

Recently, entanglement plays an important role in quantum information science. Here we propose an efficient and applicable method which transforms arbitrary three-qubit unknown state to a maximally entangled Greenberger-Horne-Zeilinger state, and the proposed method could be further generalized to multi-qubit case. The proposed setup exploits only linear optical elements and quantum non-demolition detectors using cross-Kerr media. As the quantum non-demolition detection could reveal us the output state of the photons without destroying them. This property may make our proposed setup flexible and can be widely used in current quantum information science and technology.

A quantum framework for likelihood ratios

NASA Astrophysics Data System (ADS)

Bond, Rachael L.; He, Yang-Hui; Ormerod, Thomas C.

The ability to calculate precise likelihood ratios is fundamental to science, from Quantum Information Theory through to Quantum State Estimation. However, there is no assumption-free statistical methodology to achieve this. For instance, in the absence of data relating to covariate overlap, the widely used Bayes’ theorem either defaults to the marginal probability driven “naive Bayes’ classifier”, or requires the use of compensatory expectation-maximization techniques. This paper takes an information-theoretic approach in developing a new statistical formula for the calculation of likelihood ratios based on the principles of quantum entanglement, and demonstrates that Bayes’ theorem is a special case of a more general quantum mechanical expression.

Macroscopicity of quantum superpositions on a one-parameter unitary path in Hilbert space

NASA Astrophysics Data System (ADS)

Volkoff, T. J.; Whaley, K. B.

2014-12-01

We analyze quantum states formed as superpositions of an initial pure product state and its image under local unitary evolution, using two measurement-based measures of superposition size: one based on the optimal quantum binary distinguishability of the branches of the superposition and another based on the ratio of the maximal quantum Fisher information of the superposition to that of its branches, i.e., the relative metrological usefulness of the superposition. A general formula for the effective sizes of these states according to the branch-distinguishability measure is obtained and applied to superposition states of N quantum harmonic oscillators composed of Gaussian branches. Considering optimal distinguishability of pure states on a time-evolution path leads naturally to a notion of distinguishability time that generalizes the well-known orthogonalization times of Mandelstam and Tamm and Margolus and Levitin. We further show that the distinguishability time provides a compact operational expression for the superposition size measure based on the relative quantum Fisher information. By restricting the maximization procedure in the definition of this measure to an appropriate algebra of observables, we show that the superposition size of, e.g., NOON states and hierarchical cat states, can scale linearly with the number of elementary particles comprising the superposition state, implying precision scaling inversely with the total number of photons when these states are employed as probes in quantum parameter estimation of a 1-local Hamiltonian in this algebra.

Increasing plant density in eastern United States broccoli production systems to maximize marketable head yields

USDA-ARS?s Scientific Manuscript database

Increased demand for fresh market broccoli (Brassica oleracea L. var. italica) has led to increased production along the eastern seaboard of the United States. Maximizing broccoli yields is a primary concern for quickly expanding eastern commercial markets. Thus, a plant density study was carried ...

Origins and optimization of entanglement in plasmonically coupled quantum dots

DOE PAGES

Otten, Matthew; Larson, Jeffrey; Min, Misun; ...

2016-08-11

In this paper, a system of two or more quantum dots interacting with a dissipative plasmonic nanostructure is investigated in detail by using a cavity quantum electrodynamics approach with a model Hamiltonian. We focus on determining and understanding system configurations that generate multiple bipartite quantum entanglements between the occupation states of the quantum dots. These configurations include allowing for the quantum dots to be asymmetrically coupled to the plasmonic system. Analytical solution of a simplified limit for an arbitrary number of quantum dots and numerical simulations and optimization for the two- and three-dot cases are used to develop guidelines formore » maximizing the bipartite entanglements. For any number of quantum dots, we show that through simple starting states and parameter guidelines, one quantum dot can be made to share a strong amount of bipartite entanglement with all other quantum dots in the system, while entangling all other pairs to a lesser degree.« less

A linearization of quantum channels

NASA Astrophysics Data System (ADS)

Crowder, Tanner

2015-06-01

Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.

High quantum-yield phosphors via quantum splitting and upconversion

NASA Astrophysics Data System (ADS)

Jeong, Joayoung

The Gd3+ ion has been used to induce quantum splitting in luminescent materials by using cross-relaxation energy transfer (CRET). In Nd:LiGdF4, quantum splitting results from a two-step CRET between Gd3+ and Nd3+, first involving a transition 6G→6I on Gd3+ and an excitation within the 4f3 configuration of Nd3+ followed by a second CRET that brings Gd3+ to 6P7/2. The excited Nd3+ ion rapidly relaxes nonradiatively to the emitting 4F3/2. The excited Gd3+ ion then transfers its energy back to Nd3+, which gives rise to the second photon. The result is a quantum yield of 1.05 +/- 0.35 with emission in the NIR following excitation at 175 nm. GdF3:Pr3+, Eu 3+ also exhibits quantum splitting, but only at very low concentration of Pr3+ (0.3%) and Eu3+ (0.2%), resulting in a quantum yield of approximately 20% under 160-nm excitation. Host intrinsic emission via a self-trapped exciton (STE) was also examined as a means to sensitize Gd3+ emission. The material ScPO4:Gd 3+ exhibits a high absolute quantum yield of 0.9 +/- 0.2 under 170-nm excitation, demonstrating a potentially new and efficient pathway for exciting quantum splitting phosphors. Single crystals of the material GdZrF7 were grown, and its structure was established via single-crystal X-ray diffraction methods. Doped samples of GdZrF7:Yb3+, Er3+ exhibit bright up-conversion luminescence with light output that is up to twice that of a commercial material based on the host Gd2O2S. When doped with Eu3+, the fluoride also emits a nearly white color under vacuum ultraviolet excitation with an absolute quantum yield near 0.9. The new compound Gd4.67(SiO4)3S was synthesized and studied. The structure was established via single-crystal X-ray methods, and the luminescence of Tb3+ samples was investigated.

Optimal secure quantum teleportation of coherent states of light

NASA Astrophysics Data System (ADS)

Liuzzo-Scorpo, Pietro; Adesso, Gerardo

2017-08-01

We investigate quantum teleportation of ensembles of coherent states of light with a Gaussian distributed displacement in phase space. Recently, the following general question has been addressed in [P. Liuzzo-Scorpo et al., arXiv:1705.03017]: Given a limited amount of entanglement and mean energy available as resources, what is the maximal fidelity that can be achieved on average in the teleportation of such an alphabet of states? Here, we consider a variation of this question, where Einstein-Podolsky-Rosen steering is used as a resource rather than plain entanglement. We provide a solution by means of an optimisation within the space of Gaussian quantum channels, which allows for an intuitive visualisation of the problem. We first show that not all channels are accessible with a finite degree of steering, and then prove that practical schemes relying on asymmetric two-mode Gaussian states enable one to reach the maximal fidelity at the border with the inaccessible region. Our results provide a rigorous quantitative assessment of steering as a resource for secure quantum teleportation beyond the so-called no-cloning threshold. The schemes we propose can be readily implemented experimentally by a conventional Braunstein-Kimble continuous variable teleportation protocol involving homodyne detections and corrective displacements with an optimally tuned gain. These protocols can be integrated as elementary building blocks in quantum networks, for reliable storage and transmission of quantum optical states.

Finding the quantum thermoelectric with maximal efficiency and minimal entropy production at given power output

NASA Astrophysics Data System (ADS)

Whitney, Robert S.

2015-03-01

We investigate the nonlinear scattering theory for quantum systems with strong Seebeck and Peltier effects, and consider their use as heat engines and refrigerators with finite power outputs. This paper gives detailed derivations of the results summarized in a previous paper [R. S. Whitney, Phys. Rev. Lett. 112, 130601 (2014), 10.1103/PhysRevLett.112.130601]. It shows how to use the scattering theory to find (i) the quantum thermoelectric with maximum possible power output, and (ii) the quantum thermoelectric with maximum efficiency at given power output. The latter corresponds to a minimal entropy production at that power output. These quantities are of quantum origin since they depend on system size over electronic wavelength, and so have no analog in classical thermodynamics. The maximal efficiency coincides with Carnot efficiency at zero power output, but decreases with increasing power output. This gives a fundamental lower bound on entropy production, which means that reversibility (in the thermodynamic sense) is impossible for finite power output. The suppression of efficiency by (nonlinear) phonon and photon effects is addressed in detail; when these effects are strong, maximum efficiency coincides with maximum power. Finally, we show in particular limits (typically without magnetic fields) that relaxation within the quantum system does not allow the system to exceed the bounds derived for relaxation-free systems, however, a general proof of this remains elusive.

Teleporting an unknown quantum state with unit fidelity and unit probability via a non-maximally entangled channel and an auxiliary system

NASA Astrophysics Data System (ADS)

Rashvand, Taghi

2016-11-01

We present a new scheme for quantum teleportation that one can teleport an unknown state via a non-maximally entangled channel with certainly, using an auxiliary system. In this scheme depending on the state of the auxiliary system, one can find a class of orthogonal vectors set as a basis which by performing von Neumann measurement in each element of this class Alice can teleport an unknown state with unit fidelity and unit probability. A comparison of our scheme with some previous schemes is given and we will see that our scheme has advantages that the others do not.

Long-distance practical quantum key distribution by entanglement swapping.

PubMed

Scherer, Artur; Sanders, Barry C; Tittel, Wolfgang

2011-02-14

We develop a model for practical, entanglement-based long-distance quantum key distribution employing entanglement swapping as a key building block. Relying only on existing off-the-shelf technology, we show how to optimize resources so as to maximize secret key distribution rates. The tools comprise lossy transmission links, such as telecom optical fibers or free space, parametric down-conversion sources of entangled photon pairs, and threshold detectors that are inefficient and have dark counts. Our analysis provides the optimal trade-off between detector efficiency and dark counts, which are usually competing, as well as the optimal source brightness that maximizes the secret key rate for specified distances (i.e. loss) between sender and receiver.

Photoactive High Explosives: Substituents Effects on Tetrazine Photochemistry and Photophysics

DOE PAGES

McGrane, Shawn David; Bolme, Cynthia Anne; Greenfield, Margo Torello; ...

2016-01-21

High explosives that are photoactive, i.e., can be initiated with light, offer significant advantages in reduced potential for accidental electrical initiation. In this study, we examined a series of structurally related tetrazine based photoactive high explosive materials to detail their photochemical and photophysical properties. Using photobleaching infrared absorption, we determined quantum yields of photochemistry for nanosecond pulsed excitation at 355 and 532 nm. Changes in mass spectrometry during laser irradiation in vacuum measured the evolution of gaseous products. Fluorescence spectra, quantum yields, and lifetimes were measured to observe radiative channels of energy decay that compete with photochemistry. For the 6more » materials studied, quantum yields of photochemistry ranged from <10 –5 to 0.03 and quantum yield of fluorescence ranged from <10 –3 to 0.33. In all cases, the photoexcitation nonradiatively relaxed primarily to heat, appropriate for supporting photothermal initiation processes. Lastly, the photochemistry observed was dominated by ring scission of the tetrazine, but there was evidence of more extensive multistep reactions as well.« less

Optomechanical Control of Quantum Yield in Trans-Cis Ultrafast Photoisomerization of a Retinal Chromophore Model.

PubMed

Valentini, Alessio; Rivero, Daniel; Zapata, Felipe; García-Iriepa, Cristina; Marazzi, Marco; Palmeiro, Raúl; Fdez Galván, Ignacio; Sampedro, Diego; Olivucci, Massimo; Frutos, Luis Manuel

2017-03-27

The quantum yield of a photochemical reaction is one of the most fundamental quantities in photochemistry, as it measures the efficiency of the transduction of light energy into chemical energy. Nature has evolved photoreceptors in which the reactivity of a chromophore is enhanced by its molecular environment to achieve high quantum yields. The retinal chromophore sterically constrained inside rhodopsin proteins represents an outstanding example of such a control. In a more general framework, mechanical forces acting on a molecular system can strongly modify its reactivity. Herein, we show that the exertion of tensile forces on a simplified retinal chromophore model provokes a substantial and regular increase in the trans-to-cis photoisomerization quantum yield in a counterintuitive way, as these extension forces facilitate the formation of the more compressed cis photoisomer. A rationale for the mechanochemical effect on this photoisomerization mechanism is also proposed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topological quantum buses: coherent quantum information transfer between topological and conventional qubits.

PubMed

Bonderson, Parsa; Lutchyn, Roman M

2011-04-01

We propose computing bus devices that enable quantum information to be coherently transferred between topological and conventional qubits. We describe a concrete realization of such a topological quantum bus acting between a topological qubit in a Majorana wire network and a conventional semiconductor double quantum dot qubit. Specifically, this device measures the joint (fermion) parity of these two different qubits by using the Aharonov-Casher effect in conjunction with an ancilliary superconducting flux qubit that facilitates the measurement. Such a parity measurement, together with the ability to apply Hadamard gates to the two qubits, allows one to produce states in which the topological and conventional qubits are maximally entangled and to teleport quantum states between the topological and conventional quantum systems. © 2011 American Physical Society

Maximal privacy without coherence.

PubMed

Leung, Debbie; Li, Ke; Smith, Graeme; Smolin, John A

2014-07-18

Privacy is a fundamental feature of quantum mechanics. A coherently transmitted quantum state is inherently private. Remarkably, coherent quantum communication is not a prerequisite for privacy: there are quantum channels that are too noisy to transmit any quantum information reliably that can nevertheless send private classical information. Here, we ask how much private classical information a channel can transmit if it has little quantum capacity. We present a class of channels N(d) with input dimension d(2), quantum capacity Q(N(d)) ≤ 1, and private capacity P(N(d)) = log d. These channels asymptotically saturate an interesting inequality P(N) ≤ (1/2)[log d(A) + Q(N)] for any channel N with input dimension d(A) and capture the essence of privacy stripped of the confounding influence of coherence.

Nonlocal games and optimal steering at the boundary of the quantum set

NASA Astrophysics Data System (ADS)

Zhen, Yi-Zheng; Goh, Koon Tong; Zheng, Yu-Lin; Cao, Wen-Fei; Wu, Xingyao; Chen, Kai; Scarani, Valerio

2016-08-01

The boundary between classical and quantum correlations is well characterized by linear constraints called Bell inequalities. It is much harder to characterize the boundary of the quantum set itself in the space of no-signaling correlations. For the points on the quantum boundary that violate maximally some Bell inequalities, J. Oppenheim and S. Wehner [Science 330, 1072 (2010), 10.1126/science.1192065] pointed out a complex property: Alice's optimal measurements steer Bob's local state to the eigenstate of an effective operator corresponding to its maximal eigenvalue. This effective operator is the linear combination of Bob's local operators induced by the coefficients of the Bell inequality, and it can be interpreted as defining a fine-grained uncertainty relation. It is natural to ask whether the same property holds for other points on the quantum boundary, using the Bell expression that defines the tangent hyperplane at each point. We prove that this is indeed the case for a large set of points, including some that were believed to provide counterexamples. The price to pay is to acknowledge that the Oppenheim-Wehner criterion does not respect equivalence under the no-signaling constraint: for each point, one has to look for specific forms of writing the Bell expressions.

Distance between Quantum States and Gauge-Gravity Duality.

PubMed

Miyaji, Masamichi; Numasawa, Tokiro; Shiba, Noburo; Takayanagi, Tadashi; Watanabe, Kento

2015-12-31

We study a quantum information metric (or fidelity susceptibility) in conformal field theories with respect to a small perturbation by a primary operator. We argue that its gravity dual is approximately given by a volume of maximal time slice in an anti-de Sitter spacetime when the perturbation is exactly marginal. We confirm our claim in several examples.

Long distance quantum teleportation in a quantum relay configuration.

PubMed

de Riedmatten, H; Marcikic, I; Tittel, W; Zbinden, H; Collins, D; Gisin, N

2004-01-30

A long distance quantum teleportation experiment with a fiber-delayed Bell state measurement (BSM) is reported. The source creating the qubits to be teleported and the source creating the necessary entangled state are connected to the beam splitter realizing the BSM by two 2 km long optical fibers. In addition, the teleported qubits are analyzed after 2.2 km of optical fiber, in another laboratory separated by 55 m. Time-bin qubits carried by photons at 1310 nm are teleported onto photons at 1550 nm. The fidelity is of 77%, above the maximal value obtainable without entanglement. This is the first realization of an elementary quantum relay over significant distances, which will allow an increase in the range of quantum communication and quantum key distribution.

Squeezed-state quantum key distribution with a Rindler observer

NASA Astrophysics Data System (ADS)

Zhou, Jian; Shi, Ronghua; Guo, Ying

2018-03-01

Lengthening the maximum transmission distance of quantum key distribution plays a vital role in quantum information processing. In this paper, we propose a directional squeezed-state protocol with signals detected by a Rindler observer in the relativistic quantum field framework. We derive an analytical solution to the transmission problem of squeezed states from the inertial sender to the accelerated receiver. The variance of the involved signal mode is closer to optimality than that of the coherent-state-based protocol. Simulation results show that the proposed protocol has better performance than the coherent-state counterpart especially in terms of the maximal transmission distance.

Some New Properties of Quantum Correlations

NASA Astrophysics Data System (ADS)

Liu, Feng; Li, Fei; Wei, Yunxia

2017-02-01

Quantum coherence measures the correlation between different measurement results in a single-system, while entanglement and quantum discord measure the correlation among different subsystems in a multipartite system. In this paper, we focus on the relative entropy form of them, and obtain three new properties of them as follows: 1) General forms of maximally coherent states for the relative entropy coherence, 2) Linear monogamy of the relative entropy entanglement, and 3) Subadditivity of quantum discord. Here, the linear monogamy is defined as there is a small constant as the upper bound on the sum of the relative entropy entanglement in subsystems.

Trapped-Ion Quantum Logic with Global Radiation Fields.

PubMed

Weidt, S; Randall, J; Webster, S C; Lake, K; Webb, A E; Cohen, I; Navickas, T; Lekitsch, B; Retzker, A; Hensinger, W K

2016-11-25

Trapped ions are a promising tool for building a large-scale quantum computer. However, the number of required radiation fields for the realization of quantum gates in any proposed ion-based architecture scales with the number of ions within the quantum computer, posing a major obstacle when imagining a device with millions of ions. Here, we present a fundamentally different approach for trapped-ion quantum computing where this detrimental scaling vanishes. The method is based on individually controlled voltages applied to each logic gate location to facilitate the actual gate operation analogous to a traditional transistor architecture within a classical computer processor. To demonstrate the key principle of this approach we implement a versatile quantum gate method based on long-wavelength radiation and use this method to generate a maximally entangled state of two quantum engineered clock qubits with fidelity 0.985(12). This quantum gate also constitutes a simple-to-implement tool for quantum metrology, sensing, and simulation.

Synthesis, characterization and photophysical-theoretical analysis of compounds A-π-D. 1. Effect of alkyl-phenyl substituted amines in photophysical properties

NASA Astrophysics Data System (ADS)

Ortega, E.; Montecinos, R.; Cattin, L.; Díaz, F. R.; del Valle, M. A.; Bernède, J. C.

2017-08-01

The study of new dipolar A-π-D molecules, which have an acceptor (A) and donor (D) charge joined by a conjugate bridge, have been an attention focus in the recent years due their different properties. In the current work, a molecular system has been modified in order to compare the effect on properties, such as quantum yield. Thus, two series were generated (alkyl- and alkoxy-substituted) to determine if molecules with tertiary asymmetric amines change their optical properties and whether quantum yield is affected. The different products have been characterized by several techniques such as UV-Vis spectrophotometry, elemental analysis, NMR, FT-IR, mass spectroscopy and fluorescence spectroscopy. Furthermore, their behavior in eight organic solvents, dichloromethane, tetrahydrofuran, ethyl acetate, 1,4-dioxane, acetone, acetonitrile, dimethylformamide and dimethylsulfoxide were experimentally and theoretically studied. The quantum yields were higher for the alkyl-substituted series. Theoretically, the dihedral angles formed between the tertiary amine and carbonyl group moieties have a correlation with quantum yield values, helping to explain why they are higher in non-polar solvents. Consequently, the maximum quantum yield was obtained with (E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(methyl(phenyl)amino)-9H-fluoren-2-yl) vinyl)thiophen-2-yl)acrylic acid (M8-1) in 1,4-dioxane, reaching 98.8%.

Silicon Nanoparticles with Surface Nitrogen: 90% Quantum Yield with Narrow Luminescence Bandwidth and the Ligand Structure Based Energy Law.

PubMed

Li, Qi; Luo, Tian-Yi; Zhou, Meng; Abroshan, Hadi; Huang, Jingchun; Kim, Hyung J; Rosi, Nathaniel L; Shao, Zhengzhong; Jin, Rongchao

2016-09-27

Silicon nanoparticles (NPs) have been widely accepted as an alternative material for typical quantum dots and commercial organic dyes in light-emitting and bioimaging applications owing to silicon's intrinsic merits of least toxicity, low cost, and high abundance. However, to date, how to improve Si nanoparticle photoluminescence (PL) performance (such as ultrahigh quantum yield, sharp emission peak, high stability) is still a major issue. Herein, we report surface nitrogen-capped Si NPs with PL quantum yield up to 90% and narrow PL bandwidth (full width at half-maximum (fwhm) ≈ 40 nm), which can compete with commercial dyes and typical quantum dots. Comprehensive studies have been conducted to unveil the influence of particle size, structure, and amount of surface ligand on the PL of Si NPs. Especially, a general ligand-structure-based PL energy law for surface nitrogen-capped Si NPs is identified in both experimental and theoretical analyses, and the underlying PL mechanisms are further discussed.

More bang for your buck: super-adiabatic quantum engines.

PubMed

del Campo, A; Goold, J; Paternostro, M

2014-08-28

The practical untenability of the quasi-static assumption makes any realistic engine intrinsically irreversible and its operating time finite, thus implying friction effects at short cycle times. An important technological goal is thus the design of maximally efficient engines working at the maximum possible power. We show that, by utilising shortcuts to adiabaticity in a quantum engine cycle, one can engineer a thermodynamic cycle working at finite power and zero friction. Our findings are illustrated using a harmonic oscillator undergoing a quantum Otto cycle.

More bang for your buck: Super-adiabatic quantum engines

PubMed Central

Campo, A. del; Goold, J.; Paternostro, M.

2014-01-01

The practical untenability of the quasi-static assumption makes any realistic engine intrinsically irreversible and its operating time finite, thus implying friction effects at short cycle times. An important technological goal is thus the design of maximally efficient engines working at the maximum possible power. We show that, by utilising shortcuts to adiabaticity in a quantum engine cycle, one can engineer a thermodynamic cycle working at finite power and zero friction. Our findings are illustrated using a harmonic oscillator undergoing a quantum Otto cycle. PMID:25163421

Coherent attacking continuous-variable quantum key distribution with entanglement in the middle

NASA Astrophysics Data System (ADS)

Zhang, Zhaoyuan; Shi, Ronghua; Zeng, Guihua; Guo, Ying

2018-06-01

We suggest an approach on the coherent attack of continuous-variable quantum key distribution (CVQKD) with an untrusted entangled source in the middle. The coherent attack strategy can be performed on the double links of quantum system, enabling the eavesdropper to steal more information from the proposed scheme using the entanglement correlation. Numeric simulation results show the improved performance of the attacked CVQKD system in terms of the derived secret key rate with the controllable parameters maximizing the stolen information.

Do the cations in clay and the polymer matrix affect quantum dot fluorescent properties?

PubMed

Wei, Wenjun; Liu, Cui; Liu, Jiyan; Liu, Xueqing; Zou, Linling; Cai, Shaojun; Shi, Hong; Cao, Yuan-Cheng

2016-06-01

This paper studied the effects of cations and polymer matrix on the fluorescent properties of quantum dots (QDs). The results indicated that temperature has a greater impact on fluorescence intensity than clay cations (mainly K(+) and Na(+) ). Combined fluorescence lifetime and steady-state spectrometer tests showed that QD lifetimes all decreased when the cation concentration was increased, but the quantum yields were steady at various cation concentrations of 0, 0.05, 0.5 and 1 M. Poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA) and diepoxy resin were used to study the effects of polymers on QD lifetime and quantum yield. The results showed that the lifetime for QDs 550 nm in PEO and PVA was 17.33 and 17.12 ns, respectively; for the epoxy resin, the lifetime was 0.74 ns, a sharp decrease from 24.47 ns. The quantum yield for QDs 550 nm changed from 34.22% to 7.45% and 7.81% in PEO and PVA, respectively; for the epoxy resin the quantum yield was 2.25%. QDs 580 nm and 620 nm showed the same results as QDs 550 nm. This study provides useful information on the design, synthesis and application of QDs-polymer luminescent materials. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1.

PubMed

Laisk, Agu; Oja, Vello; Eichelmann, Hillar; Dall'Osto, Luca

2014-02-01

The spectral global quantum yield (YII, electrons/photons absorbed) of photosystem II (PSII) was measured in sunflower leaves in State 1 using monochromatic light. The global quantum yield of PSI (YI) was measured using low-intensity monochromatic light flashes and the associated transmittance change at 810nm. The 810-nm signal change was calibrated based on the number of electrons generated by PSII during the flash (4·O2 evolution) which arrived at the PSI donor side after a delay of 2ms. The intrinsic quantum yield of PSI (yI, electrons per photon absorbed by PSI) was measured at 712nm, where photon absorption by PSII was small. The results were used to resolve the individual spectra of the excitation partitioning coefficients between PSI (aI) and PSII (aII) in leaves. For comparison, pigment-protein complexes for PSII and PSI were isolated, separated by sucrose density ultracentrifugation, and their optical density was measured. A good correlation was obtained for the spectral excitation partitioning coefficients measured by these different methods. The intrinsic yield of PSI was high (yI=0.88), but it absorbed only about 1/3 of quanta; consequently, about 2/3 of quanta were absorbed by PSII, but processed with the low intrinsic yield yII=0.63. In PSII, the quantum yield of charge separation was 0.89 as detected by variable fluorescence Fv/Fm, but 29% of separated charges recombined (Laisk A, Eichelmann H and Oja V, Photosynth. Res. 113, 145-155). At wavelengths less than 580nm about 30% of excitation is absorbed by pigments poorly connected to either photosystem, most likely carotenoids bound in pigment-protein complexes. Copyright © 2013 Elsevier B.V. All rights reserved.

ABSORBANCE, ABSORPTION COEFFICIENT, AND APPARENT QUANTUM YIELD: A COMMENT ON AMBIGUITY IN THE USE OF THESE OPTICAL CONCEPTS

EPA Science Inventory

Several important optical terms such as "absorbance" and "absorption coefficient" are frequently used ambiguously in the current peer-reviewed literature. Since they are important terms that are required to derive other quantities such as the "apparent quantum yield" of photoprod...

Strategies in a symmetric quantum Kolkata restaurant problem

NASA Astrophysics Data System (ADS)

Sharif, Puya; Heydari, Hoshang

2012-12-01

The Quantum Kolkata restaurant problem is a multiple-choice version of the quantum minority game, where a set of n non-communicating players have to chose between one of m choices. A payoff is granted to the players that make a unique choice. It has previously been shown that shared entanglement and quantum operations can aid the players to coordinate their actions and acquire higher payoffs than is possible with classical randomization. In this paper the initial quantum state is expanded to a family of GHZ-type states and strategies are discussed in terms of possible final outcomes. It is shown that the players individually seek outcomes that maximize the collective good.

Faithful Remote Information Concentration Based on the Optimal Universal 1→2 Telecloning of Arbitrary Two-Qubit States

NASA Astrophysics Data System (ADS)

Peng, Jia-Yin; Lei, Hong-Xuan; Mo, Zhi-Wen

2014-05-01

The previous protocols of remote quantum information concentration were focused on the reverse process of quantum telecloning of single-qubit states. We here investigate the reverse process of optimal universal 1→2 telecloning of arbitrary two-qubit states. The aim of this telecloning is to distribute respectively the quantum information to two groups of spatially separated receivers from a group of two senders situated at two different locations. Our scheme shows that the distributed quantum information can be remotely concentrated back to a group of two different receivers with 1 of probability by utilizing maximally four-particle cluster state and four-particle GHZ state as quantum channel.

Light intensity-voltage correlations and leakage-current excess noise in a single-mode semiconductor laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurin, I.; Bramati, A.; Giacobino, E.

2005-09-15

Semiconductor lasers are particularly well suited for the implementation of pump-noise suppression, yielding a reduction of the intensity noise in the laser. In this simple picture, the maximal amount of squeezing is equal to the quantum efficiency. However, experimental results on intensity noise reduction by pump-noise suppression are usually above this limit. This discrepancy suggests that additional noise sources must be involved. Here we successful y interpret the full noise behavior of a single-mode laser diode far above threshold by considering two excess noise sources: the leakage current fluctuations across the laser and the Petermann excess noise. We have estimatedmore » the contribution of each noise source using the results of the correlations between the laser output intensity noise and the voltage fluctuations across the laser diode (light-voltage correlations) and obtained good agreement between our theory and experimental results.« less

[Nanotechnology: a big revolution from the small world].

PubMed

Bassi, Matteo; Santinello, Irene; Bevilacqua, Andrea; Bassi, Pierfrancesco

2013-01-01

Nanotechnology is a multidisciplinary field originating from the interaction of several different disciplines, such as engineering, physics, biology and chemistry. New materials and devices effectively interact with the body at molecular level, yielding a brand new range of highly selective and targeted applications designed to maximize the therapeutic efficiency while reducing the side effects. Liposomes, quantum dots, carbon nanotubes and superparamagnetic nanoparticles are among the most assessed nanotechnologies. Meanwhile, other futuristic platforms are paving the way toward a new scientific paradigm, able to deeply change the research path in the medical science. The growth of nanotechnology, driven by the dramatic advances in science and technology, clearly creates new opportunities for the development of the medical science and disease treatment in human health care. Despite the concerns and the on-going studies about their safety, nanotechnology clearly emerges as holding the promise of delivering one of the greatest breakthroughs in the history of medical science.

The impacts of the quantum-dot confining potential on the spin-orbit effect.

PubMed

Li, Rui; Liu, Zhi-Hai; Wu, Yidong; Liu, C S

2018-05-09

For a nanowire quantum dot with the confining potential modeled by both the infinite and the finite square wells, we obtain exactly the energy spectrum and the wave functions in the strong spin-orbit coupling regime. We find that regardless of how small the well height is, there are at least two bound states in the finite square well: one has the σ x [Formula: see text] = -1 symmetry and the other has the σ x [Formula: see text] = 1 symmetry. When the well height is slowly tuned from large to small, the position of the maximal probability density of the first excited state moves from the center to x ≠ 0, while the position of the maximal probability density of the ground state is always at the center. A strong enhancement of the spin-orbit effect is demonstrated by tuning the well height. In particular, there exists a critical height [Formula: see text], at which the spin-orbit effect is enhanced to maximal.

Quantum Criticality and Black Holes

ScienceCinema

Sachdev, Subir [Harvard University, Cambridge, Massachusetts, United States

2017-12-09

I will describe the behavior of a variety of condensed matter systems in the vicinity of zero temperature quantum phase transitions. There is a remarkable analogy between the hydrodynamics of such systems and the quantum theory of black holes. I will show how insights from this analogy have shed light on recent experiments on the cuprate high temperature superconductors. Studies of new materials and trapped ultracold atoms are yielding new quantum phases, with novel forms of quantum entanglement. Some materials are of technological importance: e.g. high temperature superconductors. Exact solutions via black hole mapping have yielded first exact results for transport coefficients in interacting many-body systems, and were valuable in determining general structure of hydrodynamics. Theory of VBS order and Nernst effect in cuprates. Tabletop 'laboratories for the entire universe': quantum mechanics of black holes, quark-gluon plasma, neutrons stars, and big-bang physics.

Brightly Luminescent and Color-Tunable Colloidal CH3NH3PbX3 (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology.

PubMed

Zhang, Feng; Zhong, Haizheng; Chen, Cheng; Wu, Xian-gang; Hu, Xiangmin; Huang, Hailong; Han, Junbo; Zou, Bingsuo; Dong, Yuping

2015-04-28

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn(4+) as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.

No extension of quantum theory can have improved predictive power.

PubMed

Colbeck, Roger; Renner, Renato

2011-08-02

According to quantum theory, measurements generate random outcomes, in stark contrast with classical mechanics. This raises the question of whether there could exist an extension of the theory that removes this indeterminism, as suspected by Einstein, Podolsky and Rosen. Although this has been shown to be impossible, existing results do not imply that the current theory is maximally informative. Here we ask the more general question of whether any improved predictions can be achieved by any extension of quantum theory. Under the assumption that measurements can be chosen freely, we answer this question in the negative: no extension of quantum theory can give more information about the outcomes of future measurements than quantum theory itself. Our result has significance for the foundations of quantum mechanics, as well as applications to tasks that exploit the inherent randomness in quantum theory, such as quantum cryptography.

Nonlocal memory effects allow perfect teleportation with mixed states

PubMed Central

Laine, Elsi-Mari; Breuer, Heinz-Peter; Piilo, Jyrki

2014-01-01

One of the most striking consequences of quantum physics is quantum teleportation – the possibility to transfer quantum states over arbitrary distances. Since its theoretical introduction, teleportation has been demonstrated experimentally up to the distance of 143 km. In the original proposal two parties share a maximally entangled quantum state acting as a resource for the teleportation task. If, however, the state is influenced by decoherence, perfect teleportation can no longer be accomplished. Therefore, one of the current major challenges in accomplishing teleportation over long distances is to overcome the limitations imposed by decoherence and the subsequent mixedness of the resource state. Here we show that, in the presence of nonlocal memory effects, perfect quantum teleportation can be achieved even with mixed photon polarisation states. Our results imply that memory effects can be exploited in harnessing noisy quantum systems for quantum communication and that non-Markovianity is a resource for quantum information tasks. PMID:24714695

Multiparty quantum mutual information: An alternative definition

NASA Astrophysics Data System (ADS)

Kumar, Asutosh

2017-07-01

Mutual information is the reciprocal information that is common to or shared by two or more parties. Quantum mutual information for bipartite quantum systems is non-negative, and bears the interpretation of total correlation between the two subsystems. This may, however, no longer be true for three or more party quantum systems. In this paper, we propose an alternative definition of multipartite information, taking into account the shared information between two and more parties. It is non-negative, observes monotonicity under partial trace as well as completely positive maps, and equals the multipartite information measure in literature for pure states. We then define multiparty quantum discord, and give some examples. Interestingly, we observe that quantum discord increases when a measurement is performed on a large number of subsystems. Consequently, the symmetric quantum discord, which involves a measurement on all parties, reveals the maximal quantumness. This raises a question on the interpretation of measured mutual information as a classical correlation.

No extension of quantum theory can have improved predictive power

PubMed Central

Colbeck, Roger; Renner, Renato

2011-01-01

According to quantum theory, measurements generate random outcomes, in stark contrast with classical mechanics. This raises the question of whether there could exist an extension of the theory that removes this indeterminism, as suspected by Einstein, Podolsky and Rosen. Although this has been shown to be impossible, existing results do not imply that the current theory is maximally informative. Here we ask the more general question of whether any improved predictions can be achieved by any extension of quantum theory. Under the assumption that measurements can be chosen freely, we answer this question in the negative: no extension of quantum theory can give more information about the outcomes of future measurements than quantum theory itself. Our result has significance for the foundations of quantum mechanics, as well as applications to tasks that exploit the inherent randomness in quantum theory, such as quantum cryptography. PMID:21811240

Parametric source of two-photon states with a tunable degree of entanglement and mixing: Experimental preparation of Werner states and maximally entangled mixed states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cinelli, C.; Di Nepi, G.; De Martini, F.

2004-08-01

A parametric source of polarization-entangled photon pairs with striking spatial characteristics is reported. The distribution of the output electromagnetic k modes excited by spontaneous parametric down-conversion and coupled to the output detectors can be very broad. Using these states realized over a full entanglement ring output distribution, the nonlocal properties of the generated entanglement have been tested by standard Bell measurements and by Ou-Mandel interferometry. A 'mode-patchwork' technique based on the quantum superposition principle is adopted to synthesize in a straightforward and reliable way any kind of mixed state, of large conceptual and technological interest in modern quantum information. Tunablemore » Werner states and maximally entangled mixed states have indeed been created by this technique and investigated by quantum tomography. A study of the entropic and nonlocal properties of these states has been undertaken experimentally and theoretically, by a unifying variational approach.« less

Qubit absorption refrigerator at strong coupling

NASA Astrophysics Data System (ADS)

Mu, Anqi; Agarwalla, Bijay Kumar; Schaller, Gernot; Segal, Dvira

2017-12-01

We demonstrate that a quantum absorption refrigerator (QAR) can be realized from the smallest quantum system, a qubit, by coupling it in a non-additive (strong) manner to three heat baths. This function is un-attainable for the qubit model under the weak system-bath coupling limit, when the dissipation is additive. In an optimal design, the reservoirs are engineered and characterized by a single frequency component. We then obtain closed expressions for the cooling window and refrigeration efficiency, as well as bounds for the maximal cooling efficiency and the efficiency at maximal power. Our results agree with macroscopic designs and with three-level models for QARs, which are based on the weak system-bath coupling assumption. Beyond the optimal limit, we show with analytical calculations and numerical simulations that the cooling efficiency varies in a non-universal manner with model parameters. Our work demonstrates that strongly-coupled quantum machines can exhibit function that is un-attainable under the weak system-bath coupling assumption.

Fisher information in a quantum-critical environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun Zhe; Ma Jian; Lu Xiaoming

2010-08-15

We consider a process of parameter estimation in a spin-j system surrounded by a quantum-critical spin chain. Quantum Fisher information lies at the heart of the estimation task. We employ Ising spin chain in a transverse field as the environment which exhibits a quantum phase transition. Fisher information decays with time almost monotonously when the environment reaches the critical point. By choosing a fixed time or taking the time average, one can see the quantum Fisher information presents a sudden drop at the critical point. Different initial states of the environment are considered. The phenomenon that the quantum Fisher information,more » namely, the precision of estimation, changes dramatically can be used to detect the quantum criticality of the environment. We also introduce a general method to obtain the maximal Fisher information for a given state.« less

Structural Basis for Near Unity Quantum Yield Core/Shell Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

McBride, James; Treadway, Joe; Pennycook, Stephen J

2006-01-01

Aberration-corrected Z-contrast scanning transmission electron microscopy of core/shell nanocrystals shows clear correlations between structure and quantum efficiency. Uniform shell coverage is obtained only for a graded CdS/ZnS shell material and is found to be critical to achieving near 100% quantum yield. The sublattice sensitivity of the images confirms that preferential growth takes place on the anion-terminated surfaces. This explains the three-dimensional "nanobullet" shape observed in the case of core/shell nanorods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Lin; Chen Yixin

We show that no universal quantum cloning machine exists that can broadcast an arbitrary mixed qubit with a constant fidelity. Based on this result, we investigate the dependent quantum cloner in the sense that some parameter of the input qubit {rho}{sub s}({theta},{omega},{lambda}) is regarded as constant in the fidelity. For the case of constant {omega}, we establish the 1{yields}2 optimal symmetric dependent cloner with a fidelity 1/2. It is also shown that the 1{yields}M optimal quantum cloning machine for pure qubits is also optimal for mixed qubits, when {lambda} is the unique parameter in the fidelity. For general N{yields}M broadcastingmore » of mixed qubits, the situation is very different.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo

We analyze quantum algorithms for cloning of a quantum measurement. Our aim is to mimic two uses of a device performing an unknown von Neumann measurement with a single use of the device. When the unknown device has to be used before the bipartite state to be measured is available we talk about 1{yields}2 learning of the measurement, otherwise the task is called 1{yields}2 cloning of a measurement. We perform the optimization for both learning and cloning for arbitrary dimension d of the Hilbert space. For 1{yields}2 cloning we also propose a simple quantum network that achieves the optimal fidelity.more » The optimal fidelity for 1{yields}2 learning just slightly outperforms the estimate and prepare strategy in which one first estimates the unknown measurement and depending on the result suitably prepares the duplicate.« less

Rigorous quantum limits on monitoring free masses and harmonic oscillators

NASA Astrophysics Data System (ADS)

Roy, S. M.

2018-03-01

There are heuristic arguments proposing that the accuracy of monitoring position of a free mass m is limited by the standard quantum limit (SQL): σ2( X (t ) ) ≥σ2( X (0 ) ) +(t2/m2) σ2( P (0 ) ) ≥ℏ t /m , where σ2( X (t ) ) and σ2( P (t ) ) denote variances of the Heisenberg representation position and momentum operators. Yuen [Phys. Rev. Lett. 51, 719 (1983), 10.1103/PhysRevLett.51.719] discovered that there are contractive states for which this result is incorrect. Here I prove universally valid rigorous quantum limits (RQL), viz. rigorous upper and lower bounds on σ2( X (t ) ) in terms of σ2( X (0 ) ) and σ2( P (0 ) ) , given by Eq. (12) for a free mass and by Eq. (36) for an oscillator. I also obtain the maximally contractive and maximally expanding states which saturate the RQL, and use the contractive states to set up an Ozawa-type measurement theory with accuracies respecting the RQL but beating the standard quantum limit. The contractive states for oscillators improve on the Schrödinger coherent states of constant variance and may be useful for gravitational wave detection and optical communication.

Optical simulation of a Popescu-Rohrlich Box

PubMed Central

Chu, Wen-Jing; Zong, Xiao-Lan; Yang, Ming; Pan, Guo-Zhu; Cao, Zhuo-Liang

2016-01-01

It is well known that the fair-sampling loophole in Bell test opened by the selection of the state to be measured can lead to post-quantum correlations. In this paper, we make the selection of the results after measurement, which opens the fair- sampling loophole too, and thus can lead to post-quantum correlations. This kind of result-selection loophole can be realized by pre- and post-selection processes within the “two-state vector formalism”, and a physical simulation of Popescu-Rohrlich (PR) box is designed in linear optical system. The probability distribution of the PR has a maximal CHSH value 4, i.e. it can maximally violate CHSH inequality. Because the “two-state vector formalism” violates the information causality, it opens the locality loophole too, which means that this kind of results selection within “two-state vector formalism” leads to both fair- sampling loophole and locality loophole, so we call it a comprehensive loophole in Bell test. The comprehensive loophole opened by the results selection within “two-state vector formalism” may be another possible explanation of why post-quantum correlations are incompatible with quantum mechanics and seem not to exist in nature. PMID:27329203

Optical simulation of a Popescu-Rohrlich Box.

PubMed

Chu, Wen-Jing; Zong, Xiao-Lan; Yang, Ming; Pan, Guo-Zhu; Cao, Zhuo-Liang

2016-06-22

It is well known that the fair-sampling loophole in Bell test opened by the selection of the state to be measured can lead to post-quantum correlations. In this paper, we make the selection of the results after measurement, which opens the fair- sampling loophole too, and thus can lead to post-quantum correlations. This kind of result-selection loophole can be realized by pre- and post-selection processes within the "two-state vector formalism", and a physical simulation of Popescu-Rohrlich (PR) box is designed in linear optical system. The probability distribution of the PR has a maximal CHSH value 4, i.e. it can maximally violate CHSH inequality. Because the "two-state vector formalism" violates the information causality, it opens the locality loophole too, which means that this kind of results selection within "two-state vector formalism" leads to both fair- sampling loophole and locality loophole, so we call it a comprehensive loophole in Bell test. The comprehensive loophole opened by the results selection within "two-state vector formalism" may be another possible explanation of why post-quantum correlations are incompatible with quantum mechanics and seem not to exist in nature.

Early Identification of Herbicide Stress in Soybean (Glycine max (L.) Merr.) Using Chlorophyll Fluorescence Imaging Technology

PubMed Central

Li, Hui; Wang, Pei; Weber, Jonas Felix; Gerhards, Roland

2017-01-01

Herbicides may damage soybean in conventional production systems. Chlorophyll fluorescence imaging technology has been applied to identify herbicide stress in weed species a few days after application. In this study, greenhouse experiments followed by field experiments at five sites were conducted to investigate if the chlorophyll fluorescence imaging is capable of identifying herbicide stress in soybean shortly after application. Measurements were carried out from emergence until the three-to-four-leaf stage of the soybean plants. Results showed that maximal photosystem II (PS II) quantum yield and shoot dry biomass was significantly reduced in soybean by herbicides compared to the untreated control plants. The stress of PS II inhibiting herbicides occurred on the cotyledons of soybean and plants recovered after one week. The stress induced by DOXP synthase-, microtubule assembly-, or cell division-inhibitors was measured from the two-leaf stage until four-leaf stage of soybean. We could demonstrate that the chlorophyll fluorescence imaging technology is capable for detecting herbicide stress in soybean. The system can be applied under both greenhouse and field conditions. This helps farmers to select weed control strategies with less phytotoxicity in soybean and avoid yield losses due to herbicide stress. PMID:29271905

Early Identification of Herbicide Stress in Soybean (Glycine max (L.) Merr.) Using Chlorophyll Fluorescence Imaging Technology.

PubMed

Li, Hui; Wang, Pei; Weber, Jonas Felix; Gerhards, Roland

2017-12-22

Herbicides may damage soybean in conventional production systems. Chlorophyll fluorescence imaging technology has been applied to identify herbicide stress in weed species a few days after application. In this study, greenhouse experiments followed by field experiments at five sites were conducted to investigate if the chlorophyll fluorescence imaging is capable of identifying herbicide stress in soybean shortly after application. Measurements were carried out from emergence until the three-to-four-leaf stage of the soybean plants. Results showed that maximal photosystem II (PS II) quantum yield and shoot dry biomass was significantly reduced in soybean by herbicides compared to the untreated control plants. The stress of PS II inhibiting herbicides occurred on the cotyledons of soybean and plants recovered after one week. The stress induced by DOXP synthase-, microtubule assembly-, or cell division-inhibitors was measured from the two-leaf stage until four-leaf stage of soybean. We could demonstrate that the chlorophyll fluorescence imaging technology is capable for detecting herbicide stress in soybean. The system can be applied under both greenhouse and field conditions. This helps farmers to select weed control strategies with less phytotoxicity in soybean and avoid yield losses due to herbicide stress.

Recovery of maximally entangled quantum states by weak-measurement reversal

NASA Astrophysics Data System (ADS)

Maleki, Yusef; Zheltikov, Aleksei M.

2018-05-01

Maximal quantum entanglement provided by N00N states is a unique resource in the quest for the ultimate precision in physical measurements. Such states, however, are fragile and prone to decoherence. Even in weak-measurement schemes, as we demonstrate in this work, the phase super-resolution provided by N00N states is achieved at a cost of an N-fold enhancement of amplitude damping. Still, as the analysis presented here shows, a partial collapse of N00N states induced by weak measurements can be reversed, despite the dramatic, N-fold enhancement of amplitude damping, through appropriate reversal operations on the post-measurement state, enabling a full restoration of the Heisenberg-limit phase super-resolution of N00N states.

Assessment of the Maximal Split-Half Coefficient to Estimate Reliability

ERIC Educational Resources Information Center

Thompson, Barry L.; Green, Samuel B.; Yang, Yanyun

2010-01-01

The maximal split-half coefficient is computed by calculating all possible split-half reliability estimates for a scale and then choosing the maximal value as the reliability estimate. Osburn compared the maximal split-half coefficient with 10 other internal consistency estimates of reliability and concluded that it yielded the most consistently…

Influence of quantum dot's quantum yield to chemiluminescent resonance energy transfer.

PubMed

Wang, Hai-Qiao; Li, Yong-Qiang; Wang, Jian-Hao; Xu, Qiao; Li, Xiu-Qing; Zhao, Yuan-Di

2008-03-03

The resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and quantum dots (QDs, emission at 593 nm) acceptors (CRET) was investigated. The resonance energy transfer efficiencies were compared while the oil soluble QDs, water soluble QDs (modified with thioglycolate) and QD-HRP conjugates were used as acceptor. The fluorescence of QD can be observed in the three cases, indicating that the CRET occurs while QD acceptor in different status was used. The highest CRET efficiency (10.7%) was obtained in the case of oil soluble QDs, and the lowest CRET efficiency (2.7%) was observed in the QD-HRP conjugates case. This result is coincident with the quantum yields of the acceptors (18.3% and 0.4%). The same result was observed in another similar set of experiment, in which the amphiphilic polymer modified QDs (emission at 675 nm) were used. It suggests that the quantum yield of the QD in different status is the crucial factor to the CRET efficiency. Furthermore, the multiplexed CRET between luminol donor and three different sizes QD acceptors was observed simultaneously. This work will offer useful support for improving the CRET studies based on quantum dots.

Is a description deeper than the quantum one possible?

NASA Astrophysics Data System (ADS)

Ghirardi, GianCarlo; Romano, Raffaele

2014-12-01

Recently, it has been argued that quantum mechanics is a complete theory, and that different quantum states do necessarily correspond to different elements of reality, under the assumptions that quantum mechanics is correct and that measurement settings can be freely chosen. In this work, we prove that this result is a consequence of an unnecessarily strong mathematical expression of the free choice assumption, which embodies more conditions than explicitly stated. The issues of the completeness of quantum mechanics, and of the interpretation of the state vector, are by no means resolved. Taking this perspective, we describe how the recently introduced class of crypto-nonlocal hidden variables theories can be used to characterize the maximal possible departure from quantum mechanics, when the system consists of a pair of qubits.

Performance of device-independent quantum key distribution

NASA Astrophysics Data System (ADS)

Cao, Zhu; Zhao, Qi; Ma, Xiongfeng

2016-07-01

Quantum key distribution provides information-theoretically-secure communication. In practice, device imperfections may jeopardise the system security. Device-independent quantum key distribution solves this problem by providing secure keys even when the quantum devices are untrusted and uncharacterized. Following a recent security proof of the device-independent quantum key distribution, we improve the key rate by tightening the parameter choice in the security proof. In practice where the system is lossy, we further improve the key rate by taking into account the loss position information. From our numerical simulation, our method can outperform existing results. Meanwhile, we outline clear experimental requirements for implementing device-independent quantum key distribution. The maximal tolerable error rate is 1.6%, the minimal required transmittance is 97.3%, and the minimal required visibility is 96.8 % .

Amplitudes in the N=4 supersymmetric Yang-Mills theory from quantum geometry of momentum space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gorsky, A.

We discuss multiloop maximally helicity violating amplitudes in the N=4 supersymmetric Yang-Mills theory in terms of effective gravity in the momentum space with IR regulator branes as degrees of freedom. Kinematical invariants of external particles yield the moduli spaces of complex or Kahler structures which are the playgrounds for the Kodaira-Spencer or Kahler type gravity. We suggest fermionic representation of the loop maximally helicity violating amplitudes in the N=4 supersymmetric Yang-Mills theory assuming the identification of the IR regulator branes with Kodaira-Spencer fermions in the B model and Lagrangian branes in the A model. The two-easy mass box diagram ismore » related to the correlator of fermionic currents on the spectral curve in the B model or hyperbolic volume in the A model and it plays the role of a building block in the whole picture. The Bern-Dixon-Smirnov-like ansatz has the interpretation as the semiclassical limit of a fermionic correlator. It is argued that fermionic representation implies a kind of integrability on the moduli spaces. We conjecture the interpretation of the reggeon degrees of freedom in terms of the open strings stretched between the IR regulator branes.« less

Photosynthetic characteristics and mycosporine-like amino acids under UV radiation: a competitive advantage of Mastocarpus stellatus over Chondrus crispus at the Helgoland shoreline?

NASA Astrophysics Data System (ADS)

Bischof, K.; Kräbs, G.; Hanelt, D.; Wiencke, C.

2000-05-01

Chondrus crispus and Mastocarpus stellatus both inhabit the intertidal and upper sublittoral zone of Helgoland, but with C. crispus generally taking a lower position. Measurements of chlorophyll fluorescence, activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), and content and composition of UV absorbing mycosporine-like amino acids (MAAs) were conducted in the laboratory, to test whether susceptibility to UV radiation may play a role in the vertical distribution of these two species. Effective and maximal quantum yield of photochemistry as well as maximal electron transport rate (ETRmax) in C. crispus were more strongly affected by UV-B radiation than in M. stellatus. In both species, no negative effects of the respective radiation conditions were found on total activity of RubisCO. Total MAA content in M. stellatus was up to 6-fold higher than in C. crispus and the composition of MAAs in the two species was different. The results indicate that, among others, UV-B sensitivity may be a factor restricting C. crispus to the lower intertidal and upper sublittoral zone, whereas M. stellatus is better adapted to UV radiation and is therefore more competitive in the upper intertidal zone.

The Dolinar Receiver in an Information Theoretic Framework

NASA Technical Reports Server (NTRS)

Erkmen, Baris I.; Birnbaum, Kevin M.; Moision, Bruce E.; Dolinar, Samuel J.

2011-01-01

Optical communication at the quantum limit requires that measurements on the optical field be maximally informative, but devising physical measurements that accomplish this objective has proven challenging. The Dolinar receiver exemplifies a rare instance of success in distinguishing between two coherent states: an adaptive local oscillator is mixed with the signal prior to photodetection, which yields an error probability that meets the Helstrom lower bound with equality. Here we apply the same local-oscillator-based architecture with aninformation-theoretic optimization criterion. We begin with analysis of this receiver in a general framework for an arbitrary coherent-state modulation alphabet, and then we concentrate on two relevant examples. First, we study a binary antipodal alphabet and show that the Dolinar receiver's feedback function not only minimizes the probability of error, but also maximizes the mutual information. Next, we study ternary modulation consistingof antipodal coherent states and the vacuum state. We derive an analytic expression for a near-optimal local oscillator feedback function, and, via simulation, we determine its photon information efficiency (PIE). We provide the PIE versus dimensional information efficiency (DIE) trade-off curve and show that this modulation and the our receiver combination performs universally better than (generalized) on-off keying plus photoncounting, although, the advantage asymptotically vanishes as the bits-per-photon diverges towards infinity.

Spectral dependence of irreversible light-induced fluorescence quenching: Chlorophyll forms with maximal emission at 700-702 and 705-710nm as spectroscopic markers of conformational changes in the core complex.

PubMed

Nematov, Sherzod; Casazza, Anna Paola; Remelli, William; Khuvondikov, Vakhobjon; Santabarbara, Stefano

2017-07-01

The spectral dependence of the irreversible non-photochemical fluorescence quenching associated with photoinhibition in vitro has been comparatively investigated in thylakoid membranes, PSII enriched particles and PSII core complexes isolated from spinach. The analysis of the fluorescence emission spectra of dark-adapted and quenched samples as a function of the detection temperature in the 280-80K interval, indicates that Chlorophyll spectral forms having maximal emission in the 700-702nm and 705-710nm ranges gain relative intensity in concomitance with the establishment of irreversible light-induced quenching, acting thereby as spectroscopic markers. The relative enhancement of the 700-702nm and 705-710nm forms emission could be due either to an increase of their stoichiometric abundance or to their intrinsically low fluorescence quantum yields. These two factors, that can also coexist, need to be promoted by light-induced alterations in chromophore-protein as well as chromophore-chromophore interactions. The bands centred at about 701 and 706nm are also observed in the PSII core complex, suggesting their, at least partial, localisation in proximity to the reaction centre, and the occurrence of light-induced conformational changes in the core subunits. Copyright © 2017 Elsevier B.V. All rights reserved.

[Effects of water stress and temperature on gas exchange and chlorophyll fluorescence of Sinocalycanthus chinensis leaves].

PubMed

Ke, Shi-sheng; Jin, Ze-xin

2008-01-01

Sinocalycanthus chinensis is an endangered species in Sinocalycanthus, and only distributed in Zhejiang Province of China. This paper studied the photosynthetic responses of 2-year-old pot-cultured S. chinensis to different levels of water stress and temperature. The results indicated that under mild and moderate water stress, the net photosynthetic rate (Pn) of S. chinensis leaves was decreased to 92.3% and 74.3% of the control, respectively, which was mainly attributed to stomatal limitation; and under severe water stress, the Pn was decreased to 44.4% of the control, which might be mainly linked to non-stomatal limitation. The appropriate temperature for S. chinensis photosynthesis was from 20 degrees C to 28 degrees C. At 39 degrees C, the Pn, water use efficiency (WUE), and maximal photochemistry efficiency (Fv/Fm) were decreased significantly, while the dark respiration rate (Rd) and transpiration rate (Tr) were enhanced significantly. With increasing water stress and temperature, some photosynthetic parameters including light saturation point (LSP), apparent quantum yield (AQY) and maximal CO2 assimilation rate (Pmax) decreased to certain extents, while light compensation point (LCP) increased, suggesting that both severe water stress and higher temperature were the important environmental factors affecting the survival of S. chinensis.

Triazatruxene: A Rigid Central Donor Unit for a D-A3 Thermally Activated Delayed Fluorescence Material Exhibiting Sub-Microsecond Reverse Intersystem Crossing and Unity Quantum Yield via Multiple Singlet-Triplet State Pairs.

PubMed

Dos Santos, Paloma L; Ward, Jonathan S; Congrave, Daniel G; Batsanov, Andrei S; Eng, Julien; Stacey, Jessica E; Penfold, Thomas J; Monkman, Andrew P; Bryce, Martin R

2018-06-01

By inverting the common structural motif of thermally activated delayed fluorescence materials to a rigid donor core and multiple peripheral acceptors, reverse intersystem crossing (rISC) rates are demonstrated in an organic material that enables utilization of triplet excited states at faster rates than Ir-based phosphorescent materials. A combination of the inverted structure and multiple donor-acceptor interactions yields up to 30 vibronically coupled singlet and triplet states within 0.2 eV that are involved in rISC. This gives a significant enhancement to the rISC rate, leading to delayed fluorescence decay times as low as 103.9 ns. This new material also has an emission quantum yield ≈1 and a very small singlet-triplet gap. This work shows that it is possible to achieve both high photoluminescence quantum yield and fast rISC in the same molecule. Green organic light-emitting diode devices with external quantum efficiency >30% are demonstrated at 76 cd m -2 .

The Effect of Correlated Energetic Disorder on Charge Transport in Organic Semiconductors

NASA Astrophysics Data System (ADS)

Allen, Jonathan; Röding, Sebastian; Cherqui, Charles; Dunlap, David

2012-10-01

In their 1995 paper describing a Monte Carlo simulation for dissociation of an electron-hole pair in the presence of Gaussian energetic disorder, Albrect and Bäassler reported a surprising result. They found that increasing the width σ of the energetic disorder increases the quantum yield φ. They attributed this behavior to the tendency for energy fluctuations to compete against the Coulombic pair attraction, driving the electron-hole pair apart at short distances where, without disorder, recombination would be almost certain. We have expanded upon this notion, and introduced spatial correlation into the energetic disorder. By correlating the energetic disorder, we have demonstrated even larger quantum yields in simulation, attributable to the tendency of correlation to drive the charges further apart spatially than merely random disorder. Our results generally support the findings of Greenham et al. in that a larger correlation radius gives a larger quantum yield. In addition to larger quantum yield, we believe that correlated disorder could be used to create pathways for charge transport within a material, allowing the charge carrier behavior to be tuned.

Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission.

PubMed

Quan, Li Na; Zhao, Yongbiao; García de Arquer, F Pelayo; Sabatini, Randy; Walters, Grant; Voznyy, Oleksandr; Comin, Riccardo; Li, Yiying; Fan, James Z; Tan, Hairen; Pan, Jun; Yuan, Mingjian; Bakr, Osman M; Lu, Zhenghong; Kim, Dong Ha; Sargent, Edward H

2017-06-14

Organo-metal halide perovskites are a promising platform for optoelectronic applications in view of their excellent charge-transport and bandgap tunability. However, their low photoluminescence quantum efficiencies, especially in low-excitation regimes, limit their efficiency for light emission. Consequently, perovskite light-emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield, even at low excitation intensities. We tailor the composition of quasi-2D perovskites to direct the energy transfer into the lowest-bandgap minority phase and to do so faster than it is lost to nonradiative centers. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm 2 , yielding a ratio of quantum yield to excitation intensity of 0.3 cm 2 /mW; this represents a decrease of 2 orders of magnitude in the excitation power required to reach high efficiency compared with the best prior reports. Using this strategy, we report light-emitting diodes with external quantum efficiencies of 7.4% and a high luminescence of 8400 cd/m 2 .

Quantum controlled-Z gate for weakly interacting qubits

NASA Astrophysics Data System (ADS)

Mičuda, Michal; Stárek, Robert; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Ježek, Miroslav; Filip, Radim; Fiurášek, Jaromír

2015-08-01

We propose and experimentally demonstrate a scheme for the implementation of a maximally entangling quantum controlled-Z gate between two weakly interacting systems. We conditionally enhance the interqubit coupling by quantum interference. Both before and after the interqubit interaction, one of the qubits is coherently coupled to an auxiliary quantum system, and finally it is projected back onto qubit subspace. We experimentally verify the practical feasibility of this technique by using a linear optical setup with weak interferometric coupling between single-photon qubits. Our procedure is universally applicable to a wide range of physical platforms including hybrid systems such as atomic clouds or optomechanical oscillators coupled to light.

Quantum localization and bound-state formation in Bose-Einstein condensates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franzosi, Roberto; Giampaolo, Salvatore M.; Illuminati, Fabrizio

2010-12-15

We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity andmore » a bounded energy spectrum.« less

Multi-objective optimization in quantum parameter estimation

NASA Astrophysics Data System (ADS)

Gong, BeiLi; Cui, Wei

2018-04-01

We investigate quantum parameter estimation based on linear and Kerr-type nonlinear controls in an open quantum system, and consider the dissipation rate as an unknown parameter. We show that while the precision of parameter estimation is improved, it usually introduces a significant deformation to the system state. Moreover, we propose a multi-objective model to optimize the two conflicting objectives: (1) maximizing the Fisher information, improving the parameter estimation precision, and (2) minimizing the deformation of the system state, which maintains its fidelity. Finally, simulations of a simplified ɛ-constrained model demonstrate the feasibility of the Hamiltonian control in improving the precision of the quantum parameter estimation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vertesi, T.; Bene, E.

A bipartite Bell inequality is derived which is maximally violated on the two-qubit state space if measurements describable by positive operator valued measure (POVM) elements are allowed, rather than restricting the possible measurements to projective ones. In particular, the presented Bell inequality requires POVMs in order to be maximally violated by a maximally entangled two-qubit state. This answers a question raised by N. Gisin [in Quantum Reality, Relativistic Causality, and Closing the Epistemic Circle: Essays in Honour of Abner Shimony, edited by W. C. Myrvold and J. Christian (Springer, The Netherlands, 2009), pp. 125-138].

Measurement of fluorophore concentrations and fluorescence quantum yield in tissue-simulating phantoms using three diffusion models of steady-state spatially resolved fluorescence.

PubMed

Diamond, Kevin R; Farrell, Thomas J; Patterson, Michael S

2003-12-21

Steady-state diffusion theory models of fluorescence in tissue have been investigated for recovering fluorophore concentrations and fluorescence quantum yield. Spatially resolved fluorescence, excitation and emission reflectance Carlo simulations, and measured using a multi-fibre probe on tissue-simulating phantoms containing either aluminium phthalocyanine tetrasulfonate (AlPcS4), Photofrin meso-tetra-(4-sulfonatophenyl)-porphine dihydrochloride The accuracy of the fluorophore concentration and fluorescence quantum yield recovered by three different models of spatially resolved fluorescence were compared. The models were based on: (a) weighted difference of the excitation and emission reflectance, (b) fluorescence due to a point excitation source or (c) fluorescence due to a pencil beam excitation source. When literature values for the fluorescence quantum yield were used for each of the fluorophores, the fluorophore absorption coefficient (and hence concentration) at the excitation wavelength (mu(a,x,f)) was recovered with a root-mean-square accuracy of 11.4% using the point source model of fluorescence and 8.0% using the more complicated pencil beam excitation model. The accuracy was calculated over a broad range of optical properties and fluorophore concentrations. The weighted difference of reflectance model performed poorly, with a root-mean-square error in concentration of about 50%. Monte Carlo simulations suggest that there are some situations where the weighted difference of reflectance is as accurate as the other two models, although this was not confirmed experimentally. Estimates of the fluorescence quantum yield in multiple scattering media were also made by determining mu(a,x,f) independently from the fitted absorption spectrum and applying the various diffusion theory models. The fluorescence quantum yields for AlPcS4 and TPPS4 were calculated to be 0.59 +/- 0.03 and 0.121 +/- 0.001 respectively using the point source model, and 0.63 +/- 0.03 and 0.129 +/- 0.002 using the pencil beam excitation model. These results are consistent with published values.

Quantum incompatibility of channels with general outcome operator algebras

NASA Astrophysics Data System (ADS)

Kuramochi, Yui

2018-04-01

A pair of quantum channels is said to be incompatible if they cannot be realized as marginals of a single channel. This paper addresses the general structure of the incompatibility of completely positive channels with a fixed quantum input space and with general outcome operator algebras. We define a compatibility relation for such channels by identifying the composite outcome space as the maximal (projective) C*-tensor product of outcome algebras. We show theorems that characterize this compatibility relation in terms of the concatenation and conjugation of channels, generalizing the recent result for channels with quantum outcome spaces. These results are applied to the positive operator valued measures (POVMs) by identifying each of them with the corresponding quantum-classical (QC) channel. We also give a characterization of the maximality of a POVM with respect to the post-processing preorder in terms of the conjugate channel of the QC channel. We consider another definition of compatibility of normal channels by identifying the composite outcome space with the normal tensor product of the outcome von Neumann algebras. We prove that for a given normal channel, the class of normally compatible channels is upper bounded by a special class of channels called tensor conjugate channels. We show the inequivalence of the C*- and normal compatibility relations for QC channels, which originates from the possibility and impossibility of copying operations for commutative von Neumann algebras in C*- and normal compatibility relations, respectively.

Satisfying the Einstein-Podolsky-Rosen criterion with massive particles

NASA Astrophysics Data System (ADS)

Peise, J.; Kruse, I.; Lange, K.; Lücke, B.; Pezzè, L.; Arlt, J.; Ertmer, W.; Hammerer, K.; Santos, L.; Smerzi, A.; Klempt, C.

2016-03-01

In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of quantum mechanics by devising a quantum state of two massive particles with maximally correlated space and momentum coordinates. The EPR criterion qualifies such continuous-variable entangled states, as shown successfully with light fields. Here, we report on the production of massive particles which meet the EPR criterion for continuous phase/amplitude variables. The created quantum state of ultracold atoms shows an EPR parameter of 0.18(3), which is 2.4 standard deviations below the threshold of 1/4. Our state presents a resource for tests of quantum nonlocality with massive particles and a wide variety of applications in the field of continuous-variable quantum information and metrology.

Fisher-Symmetric Informationally Complete Measurements for Pure States.

PubMed

Li, Nan; Ferrie, Christopher; Gross, Jonathan A; Kalev, Amir; Caves, Carlton M

2016-05-06

We introduce a new kind of quantum measurement that is defined to be symmetric in the sense of uniform Fisher information across a set of parameters that uniquely represent pure quantum states in the neighborhood of a fiducial pure state. The measurement is locally informationally complete-i.e., it uniquely determines these parameters, as opposed to distinguishing two arbitrary quantum states-and it is maximal in the sense of a multiparameter quantum Cramér-Rao bound. For a d-dimensional quantum system, requiring only local informational completeness allows us to reduce the number of outcomes of the measurement from a minimum close to but below 4d-3, for the usual notion of global pure-state informational completeness, to 2d-1.

Cryogenic on-chip multiplexer for the study of quantum transport in 256 split-gate devices

NASA Astrophysics Data System (ADS)

Al-Taie, H.; Smith, L. W.; Xu, B.; See, P.; Griffiths, J. P.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Kelly, M. J.; Smith, C. G.

2013-06-01

We present a multiplexing scheme for the measurement of large numbers of mesoscopic devices in cryogenic systems. The multiplexer is used to contact an array of 256 split gates on a GaAs/AlGaAs heterostructure, in which each split gate can be measured individually. The low-temperature conductance of split-gate devices is governed by quantum mechanics, leading to the appearance of conductance plateaux at intervals of 2e2/h. A fabrication-limited yield of 94% is achieved for the array, and a "quantum yield" is also defined, to account for disorder affecting the quantum behaviour of the devices. The quantum yield rose from 55% to 86% after illuminating the sample, explained by the corresponding increase in carrier density and mobility of the two-dimensional electron gas. The multiplexer is a scalable architecture, and can be extended to other forms of mesoscopic devices. It overcomes previous limits on the number of devices that can be fabricated on a single chip due to the number of electrical contacts available, without the need to alter existing experimental set ups.

Fast Entanglement Establishment via Local Dynamics for Quantum Repeater Networks

NASA Astrophysics Data System (ADS)

Gyongyosi, Laszlo; Imre, Sandor

Quantum entanglement is a necessity for future quantum communication networks, quantum internet, and long-distance quantum key distribution. The current approaches of entanglement distribution require high-delay entanglement transmission, entanglement swapping to extend the range of entanglement, high-cost entanglement purification, and long-lived quantum memories. We introduce a fundamental protocol for establishing entanglement in quantum communication networks. The proposed scheme does not require entanglement transmission between the nodes, high-cost entanglement swapping, entanglement purification, or long-lived quantum memories. The protocol reliably establishes a maximally entangled system between the remote nodes via dynamics generated by local Hamiltonians. The method eliminates the main drawbacks of current schemes allowing fast entanglement establishment with a minimized delay. Our solution provides a fundamental method for future long-distance quantum key distribution, quantum repeater networks, quantum internet, and quantum-networking protocols. This work was partially supported by the GOP-1.1.1-11-2012-0092 project sponsored by the EU and European Structural Fund, by the Hungarian Scientific Research Fund - OTKA K-112125, and by the COST Action MP1006.

Complexation and toxicity of copper in higher plants. I. Characterization of copper accumulation, speciation, and toxicity in Crassula helmsii as a new copper accumulator.

PubMed

Küpper, Hendrik; Götz, Birgit; Mijovilovich, Ana; Küpper, Frithjof C; Meyer-Klaucke, Wolfram

2009-10-01

The amphibious water plant Crassula helmsii is an invasive copper (Cu)-tolerant neophyte in Europe. It now turned out to accumulate Cu up to more than 9,000 ppm in its shoots at 10 microm (=0.6 ppm) Cu(2+) in the nutrient solution, indicating that it is a Cu hyperaccumulator. We investigated uptake, binding environment, and toxicity of Cu in this plant under emerged and submerged conditions. Extended x-ray absorption fine structure measurements on frozen-hydrated samples revealed that Cu was bound almost exclusively by oxygen ligands, likely organic acids, and not any sulfur ligands. Despite significant differences in photosynthesis biochemistry and biophysics between emerged and submerged plants, no differences in Cu ligands were found. While measurements of tissue pH confirmed the diurnal acid cycle typical for Crassulacean acid metabolism, Delta(13)C measurements showed values typical for regular C3 photosynthesis. Cu-induced inhibition of photosynthesis mainly affected the photosystem II (PSII) reaction center, but with some unusual features. Most obviously, the degree of light saturation of electron transport increased during Cu stress, while maximal dark-adapted PSII quantum yield did not change and light-adapted quantum yield of PSII photochemistry decreased particularly in the first 50 s after onset of actinic irradiance. This combination of changes, which were strongest in submerged cultures, shows a decreasing number of functional reaction centers relative to the antenna in a system with high antenna connectivity. Nonphotochemical quenching, in contrast, was modified by Cu mainly in emerged cultures. Pigment concentrations in stressed plants strongly decreased, but no changes in their ratios occurred, indicating that cells either survived intact or died and bleached quickly.

Quantum Prisoners' Dilemma in Fluctuating Massless Scalar Field

NASA Astrophysics Data System (ADS)

Huang, Zhiming

2017-12-01

Quantum systems are easily affected by external environment. In this paper, we investigate the influences of external massless scalar field to quantum Prisoners' Dilemma (QPD) game. We firstly derive the master equation that describes the system evolution with initial maximally entangled state. Then, we discuss the effects of a fluctuating massless scalar field on the game's properties such as payoff, Nash equilibrium, and symmetry. We find that for different game strategies, vacuum fluctuation has different effects on payoff. Nash equilibrium is broken but the symmetry of the game is not violated.

Adaptation to high CO2 concentration in an optimal environment: radiation capture, canopy quantum yield and carbon use efficiency

NASA Technical Reports Server (NTRS)

Monje, O.; Bugbee, B.

1998-01-01

The effect of elevated [CO2] on wheat (Triticum aestivum L. Veery 10) productivity was examined by analysing radiation capture, canopy quantum yield, canopy carbon use efficiency, harvest index and daily C gain. Canopies were grown at either 330 or 1200 micromoles mol-1 [CO2] in controlled environments, where root and shoot C fluxes were monitored continuously from emergence to harvest. A rapidly circulating hydroponic solution supplied nutrients, water and root zone oxygen. At harvest, dry mass predicted from gas exchange data was 102.8 +/- 4.7% of the observed dry mass in six trials. Neither radiation capture efficiency nor carbon use efficiency were affected by elevated [CO2], but yield increased by 13% due to a sustained increase in canopy quantum yield. CO2 enrichment increased root mass, tiller number and seed mass. Harvest index and chlorophyll concentration were unchanged, but CO2 enrichment increased average life cycle net photosynthesis (13%, P < 0.05) and root respiration (24%, P < 0.05). These data indicate that plant communities adapt to CO2 enrichment through changes in C allocation. Elevated [CO2] increases sink strength in optimal environments, resulting in sustained increases in photosynthetic capacity, canopy quantum yield and daily C gain throughout the life cycle.

Advances of two-stage riser catalytic cracking of heavy oil for maximizing propylene yield (TMP) process.

PubMed

Chaohe, Yang; Xiaobo, Chen; Jinhong, Zhang; Chunyi, Li; Honghong, Shan

Two-stage riser catalytic cracking of heavy oil for maximizing propylene yield (TMP) process proposed by State Key Laboratory of Heavy oil Processing, China University of Petroleum, can remarkably enhance the propylene yield and minimize the dry gas and coke yields, and obtain high-quality light oils (gasoline and diesel). It has been commercialized since 2006. Up to now, three TMP commercial units have been put into production and other four commercial units are under design and construction. The commercial data showed that taking paraffinic based Daqing (China) atmospheric residue as the feedstock, the propylene yield reached 20.31 wt%, the liquid products yield (the total yield of liquefied petroleum gas, gasoline, and diesel) was 82.66 wt%, and the total yield of dry gas and coke was 14.28 wt%. Moreover, the research octane number of gasoline could be up to 96.

Multiphoton entanglement concentration and quantum cryptography.

PubMed

Durkin, Gabriel A; Simon, Christoph; Bouwmeester, Dik

2002-05-06

Multiphoton states from parametric down-conversion can be entangled both in polarization and photon number. Maximal high-dimensional entanglement can be concentrated postselectively from these states via photon counting. This makes them natural candidates for quantum key distribution, where the presence of more than one photon per detection interval has up to now been considered undesirable. We propose a simple multiphoton cryptography protocol for the case of low losses.

Squeezing of magnetic flux in nanorings.

PubMed

Dajka, J; Ptok, A; Luczka, J

2012-12-12

We study superconducting and non-superconducting nanorings and look for non-classical features of magnetic flux passing through nanorings. We show that the magnetic flux can exhibit purely quantum properties in some peculiar states with quadrature squeezing. We identify a subset of Gazeau-Klauder states in which the magnetic flux can be squeezed and, within tailored parameter regimes, quantum fluctuations of the magnetic flux can be maximally reduced.

Rigidifying fluorescent linkers by metal-organic framework formation for fluorescence blue shift and quantum yield enhancement.

PubMed

Wei, Zhangwen; Gu, Zhi-Yuan; Arvapally, Ravi K; Chen, Ying-Pin; McDougald, Roy N; Ivy, Joshua F; Yakovenko, Andrey A; Feng, Dawei; Omary, Mohammad A; Zhou, Hong-Cai

2014-06-11

We demonstrate that rigidifying the structure of fluorescent linkers by structurally constraining them in metal-organic frameworks (MOFs) to control their conformation effectively tunes the fluorescence energy and enhances the quantum yield. Thus, a new tetraphenylethylene-based zirconium MOF exhibits a deep-blue fluorescent emission at 470 nm with a unity quantum yield (99.9 ± 0.5%) under Ar, representing ca. 3600 cm(-1) blue shift and doubled radiative decay efficiency vs the linker precursor. An anomalous increase in the fluorescence lifetime and relative intensity takes place upon heating the solid MOF from cryogenic to ambient temperatures. The origin of these unusual photoluminescence properties is attributed to twisted linker conformation, intramolecular hindrance, and framework rigidity.

The reaction of NH2 with NO2

NASA Technical Reports Server (NTRS)

Jayanty, R. K. M.; Simonaitis, R.; Heicklen, J.

1976-01-01

Ammonia (NH3) was photolyzed at 213.9 nm in the presence of NO2 at 25 C in order to study the reactions of NH2 with NO2. The products included NO, with a quantum yield of 1.0. The other measured products of the reaction were N2 and N2O with respective quantum yields of 0.94 plus or minus 0.10 and 0.3 in the presence of small amounts of He and 0.65 plus or minus 0.15 and 0.13 in the presence of a large excess of He. The quantum yield for NO2 consumption was 6.0 plus or minus 2.0 in the absence of He. These results are explained in terms of various reactions.

Greenberger-Horne-Zeilinger states-based blind quantum computation with entanglement concentration.

PubMed

Zhang, Xiaoqian; Weng, Jian; Lu, Wei; Li, Xiaochun; Luo, Weiqi; Tan, Xiaoqing

2017-09-11

In blind quantum computation (BQC) protocol, the quantum computability of servers are complicated and powerful, while the clients are not. It is still a challenge for clients to delegate quantum computation to servers and keep the clients' inputs, outputs and algorithms private. Unfortunately, quantum channel noise is unavoidable in the practical transmission. In this paper, a novel BQC protocol based on maximally entangled Greenberger-Horne-Zeilinger (GHZ) states is proposed which doesn't need a trusted center. The protocol includes a client and two servers, where the client only needs to own quantum channels with two servers who have full-advantage quantum computers. Two servers perform entanglement concentration used to remove the noise, where the success probability can almost reach 100% in theory. But they learn nothing in the process of concentration because of the no-signaling principle, so this BQC protocol is secure and feasible.

Complementarity of information and the emergence of the classical world

NASA Astrophysics Data System (ADS)

Zwolak, Michael; Zurek, Wojciech

2013-03-01

We prove an anti-symmetry property relating accessible information about a system through some auxiliary system F and the quantum discord with respect to a complementary system F'. In Quantum Darwinism, where fragments of the environment relay information to observers - this relation allows us to understand some fundamental properties regarding correlations between a quantum system and its environment. First, it relies on a natural separation of accessible information and quantum information about a system. Under decoherence, this separation shows that accessible information is maximized for the quasi-classical pointer observable. Other observables are accessible only via correlations with the pointer observable. Second, It shows that objective information becomes accessible to many observers only when quantum information is relegated to correlations with the global environment, and, therefore, locally inaccessible. The resulting complementarity explains why, in a quantum Universe, we perceive objective classical reality, and supports Bohr's intuition that quantum phenomena acquire classical reality only when communicated.

The entropic cost of quantum generalized measurements

NASA Astrophysics Data System (ADS)

Mancino, Luca; Sbroscia, Marco; Roccia, Emanuele; Gianani, Ilaria; Somma, Fabrizia; Mataloni, Paolo; Paternostro, Mauro; Barbieri, Marco

2018-03-01

Landauer's principle introduces a symmetry between computational and physical processes: erasure of information, a logically irreversible operation, must be underlain by an irreversible transformation dissipating energy. Monitoring micro- and nano-systems needs to enter into the energetic balance of their control; hence, finding the ultimate limits is instrumental to the development of future thermal machines operating at the quantum level. We report on the experimental investigation of a lower bound to the irreversible entropy associated to generalized quantum measurements on a quantum bit. We adopted a quantum photonics gate to implement a device interpolating from the weakly disturbing to the fully invasive and maximally informative regime. Our experiment prompted us to introduce a bound taking into account both the classical result of the measurement and the outcoming quantum state; unlike previous investigation, our entropic bound is based uniquely on measurable quantities. Our results highlight what insights the information-theoretic approach provides on building blocks of quantum information processors.

Quantum thermalization through entanglement in an isolated many-body system.

PubMed

Kaufman, Adam M; Tai, M Eric; Lukin, Alexander; Rispoli, Matthew; Schittko, Robert; Preiss, Philipp M; Greiner, Markus

2016-08-19

Statistical mechanics relies on the maximization of entropy in a system at thermal equilibrium. However, an isolated quantum many-body system initialized in a pure state remains pure during Schrödinger evolution, and in this sense it has static, zero entropy. We experimentally studied the emergence of statistical mechanics in a quantum state and observed the fundamental role of quantum entanglement in facilitating this emergence. Microscopy of an evolving quantum system indicates that the full quantum state remains pure, whereas thermalization occurs on a local scale. We directly measured entanglement entropy, which assumes the role of the thermal entropy in thermalization. The entanglement creates local entropy that validates the use of statistical physics for local observables. Our measurements are consistent with the eigenstate thermalization hypothesis. Copyright © 2016, American Association for the Advancement of Science.

Irreversibility and entanglement spectrum statistics in quantum circuits

NASA Astrophysics Data System (ADS)

Shaffer, Daniel; Chamon, Claudio; Hamma, Alioscia; Mucciolo, Eduardo R.

2014-12-01

We show that in a quantum system evolving unitarily under a stochastic quantum circuit the notions of irreversibility, universality of computation, and entanglement are closely related. As the state evolves from an initial product state, it gets asymptotically maximally entangled. We define irreversibility as the failure of searching for a disentangling circuit using a Metropolis-like algorithm. We show that irreversibility corresponds to Wigner-Dyson statistics in the level spacing of the entanglement eigenvalues, and that this is obtained from a quantum circuit made from a set of universal gates for quantum computation. If, on the other hand, the system is evolved with a non-universal set of gates, the statistics of the entanglement level spacing deviates from Wigner-Dyson and the disentangling algorithm succeeds. These results open a new way to characterize irreversibility in quantum systems.

Adiabatically modeling quantum gates with two-site Heisenberg spins chain: Noise vs interferometry

NASA Astrophysics Data System (ADS)

Jipdi, M. N.; Tchoffo, M.; Fai, L. C.

2018-02-01

We study the Landau Zener (LZ) dynamics of a two-site Heisenberg spin chain assisted with noise and focus on the implementation of logic gates via the resulting quantum interference. We present the evidence of the quantum interference phenomenon in triplet spin states and confirm that, three-level systems mimic Landau-Zener-Stückelberg (LZS) interferometers with occupancies dependent on the effective phase. It emerges that, the critical parameters tailoring the system are obtained for constructive interferences where the two sets of the chain are found to be maximally entangled. Our findings demonstrate that the enhancement of the magnetic field strength suppresses noise effects; consequently, the noise severely impacts the occurrence of quantum interference for weak magnetic fields while for strong fields, quantum interference subsists and allows the modeling of universal sets of quantum gates.

Recurrent neural network approach to quantum signal: coherent state restoration for continuous-variable quantum key distribution

NASA Astrophysics Data System (ADS)

Lu, Weizhao; Huang, Chunhui; Hou, Kun; Shi, Liting; Zhao, Huihui; Li, Zhengmei; Qiu, Jianfeng

2018-05-01

In continuous-variable quantum key distribution (CV-QKD), weak signal carrying information transmits from Alice to Bob; during this process it is easily influenced by unknown noise which reduces signal-to-noise ratio, and strongly impacts reliability and stability of the communication. Recurrent quantum neural network (RQNN) is an artificial neural network model which can perform stochastic filtering without any prior knowledge of the signal and noise. In this paper, a modified RQNN algorithm with expectation maximization algorithm is proposed to process the signal in CV-QKD, which follows the basic rule of quantum mechanics. After RQNN, noise power decreases about 15 dBm, coherent signal recognition rate of RQNN is 96%, quantum bit error rate (QBER) drops to 4%, which is 6.9% lower than original QBER, and channel capacity is notably enlarged.

Quantization with maximally degenerate Poisson brackets: the harmonic oscillator!

NASA Astrophysics Data System (ADS)

Nutku, Yavuz

2003-07-01

Nambu's construction of multi-linear brackets for super-integrable systems can be thought of as degenerate Poisson brackets with a maximal set of Casimirs in their kernel. By introducing privileged coordinates in phase space these degenerate Poisson brackets are brought to the form of Heisenberg's equations. We propose a definition for constructing quantum operators for classical functions, which enables us to turn the maximally degenerate Poisson brackets into operators. They pose a set of eigenvalue problems for a new state vector. The requirement of the single-valuedness of this eigenfunction leads to quantization. The example of the harmonic oscillator is used to illustrate this general procedure for quantizing a class of maximally super-integrable systems.

Maximizers in Lipschitz spacetimes are either timelike or null

NASA Astrophysics Data System (ADS)

Graf, Melanie; Ling, Eric

2018-04-01

We prove that causal maximizers in C 0,1 spacetimes are either timelike or null. This question was posed in Sämann and Steinbauer (2017 arXiv:1710.10887) since bubbling regions in C0, α spacetimes (α <1 ) can produce causal maximizers that contain a segment which is timelike and a segment which is null, see Chruściel and Grant (2012 Class. Quantum Grav. 29 145001). While C 0,1 spacetimes do not produce bubbling regions, the causal character of maximizers for spacetimes with regularity at least C 0,1 but less than C 1,1 was unknown until now. As an application we show that timelike geodesically complete spacetimes are C 0,1-inextendible.

Dephasing-covariant operations enable asymptotic reversibility of quantum resources

NASA Astrophysics Data System (ADS)

Chitambar, Eric

2018-05-01

We study the power of dephasing-covariant operations in the resource theories of coherence and entanglement. These are quantum operations whose actions commute with a projective measurement. In the resource theory of coherence, we find that any two states are asymptotically interconvertible under dephasing-covariant operations. This provides a rare example of a resource theory in which asymptotic reversibility can be attained without needing the maximal set of resource nongenerating operations. When extended to the resource theory of entanglement, the resultant operations share similarities with local operations and classical communication, such as prohibiting the increase of all Rényi α -entropies of entanglement under pure-state transformations. However, we show these operations are still strong enough to enable asymptotic reversibility between any two maximally correlated mixed states, even in the multipartite setting.

Reassessment of the nonlocality of correlation boxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costa, A.P.; Parisio, Fernando, E-mail: parisio@df.ufpe.br

Correlation boxes are hypothetical systems usually designed to produce the maximal algebraic violation of a Bell inequality, beyond the quantum bound and without superluminal signalling. The fact that these systems show stronger correlations than those presented by maximally entangled quantum states, as the spin singlet, has been regarded as a demonstration that the former are more nonlocal than the latter. By applying an alternative, consistent measure of nonlocality to a family of correlation boxes, we show that this conclusion is not necessarily true. Complementarily, we define a class of systems displaying subquantum correlations which, nevertheless, are more nonlocal than themore » singlet state, showing that the extent of the numeric violation of an inequality may have little to do with the degree of nonlocality, especially in the case of correlation boxes.« less

Benchmarking the D-Wave Two

NASA Astrophysics Data System (ADS)

Job, Joshua; Wang, Zhihui; Rønnow, Troels; Troyer, Matthias; Lidar, Daniel

2014-03-01

We report on experimental work benchmarking the performance of the D-Wave Two programmable annealer on its native Ising problem, and a comparison to available classical algorithms. In this talk we will focus on the comparison with an algorithm originally proposed and implemented by Alex Selby. This algorithm uses dynamic programming to repeatedly optimize over randomly selected maximal induced trees of the problem graph starting from a random initial state. If one is looking for a quantum advantage over classical algorithms, one should compare to classical algorithms which are designed and optimized to maximally take advantage of the structure of the type of problem one is using for the comparison. In that light, this classical algorithm should serve as a good gauge for any potential quantum speedup for the D-Wave Two.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stark, Christopher C.; Roberge, Aki; Mandell, Avi

ExoEarth yield is a critical science metric for future exoplanet imaging missions. Here we estimate exoEarth candidate yield using single visit completeness for a variety of mission design and astrophysical parameters. We review the methods used in previous yield calculations and show that the method choice can significantly impact yield estimates as well as how the yield responds to mission parameters. We introduce a method, called Altruistic Yield Optimization, that optimizes the target list and exposure times to maximize mission yield, adapts maximally to changes in mission parameters, and increases exoEarth candidate yield by up to 100% compared to previousmore » methods. We use Altruistic Yield Optimization to estimate exoEarth candidate yield for a large suite of mission and astrophysical parameters using single visit completeness. We find that exoEarth candidate yield is most sensitive to telescope diameter, followed by coronagraph inner working angle, followed by coronagraph contrast, and finally coronagraph contrast noise floor. We find a surprisingly weak dependence of exoEarth candidate yield on exozodi level. Additionally, we provide a quantitative approach to defining a yield goal for future exoEarth-imaging missions.« less

Seasonal and spatial variabilities in the water chemistry of prairie pothole wetlands influence the photoproduction of reactive intermediates.

PubMed

McCabe, Andrew J; Arnold, William A

2016-07-01

The hydrology and water chemistry of prairie pothole wetlands vary spatially and temporally, on annual and decadal timescales. Pesticide contamination of wetlands arising from agricultural activities is a foremost concern. Photochemical reactions are important in the natural attenuation of pesticides and may be important in limiting ecological and human exposure. Little is known, however, about the variable influence of wetland water chemistry on indirect photochemistry. In this study, seasonal water samples were collected from seven sites throughout the prairie pothole region over three years to understand the spatiotemporal dynamics of reactive intermediate photoproduction. Samples were classified by the season in which they were collected (spring, summer, or fall) and the typical hydroperiod of the wetland surface water (temporary or semi-permanent). Under photostable conditions, steady-state concentrations and apparent quantum yields or quantum yield coefficients were measured for triplet excited states of dissolved organic matter, singlet oxygen, hydroxyl radical, and carbonate radical under simulated sunlight. Steady-state concentrations and quantum yields increased on average by 15% and 40% from spring to fall, respectively. Temporary wetlands had 40% higher steady-state concentrations of reactive intermediates than semi-permanent wetlands, but 50% lower quantum yields. Computed quantum yields for reactive intermediate formation were used to predict the indirect photochemical half-lives of seven pesticides in average temporary and semi-permanent prairie pothole wetlands. As a first approximation, the predictions agree to within two orders of magnitude of previously reported half-lives. Copyright © 2016 Elsevier Ltd. All rights reserved.

Generalized Weyl-Wigner map and Vey quantum mechanics

NASA Astrophysics Data System (ADS)

Dias, Nuno Costa; Prata, João Nuno

2001-12-01

The Weyl-Wigner map yields the entire structure of Moyal quantum mechanics directly from the standard operator formulation. The covariant generalization of Moyal theory, also known as Vey quantum mechanics, was presented in the literature many years ago. However, a derivation of the formalism directly from standard operator quantum mechanics, clarifying the relation between the two formulations, is still missing. In this article we present a covariant generalization of the Weyl order prescription and of the Weyl-Wigner map and use them to derive Vey quantum mechanics directly from the standard operator formulation. The procedure displays some interesting features: it yields all the key ingredients and provides a more straightforward interpretation of the Vey theory including a direct implementation of unitary operator transformations as phase space coordinate transformations in the Vey idiom. These features are illustrated through a simple example.

Relativistic quantum games in noninertial frames

NASA Astrophysics Data System (ADS)

Khan, Salman; Khalid Khan, M.

2011-09-01

We study the influence of the Unruh effect on quantum non-zero sum games. In particular, we investigate the quantum Prisoners’ Dilemma both for entangled and unentangled initial states and show that the acceleration of the noninertial frames disturbs the symmetry of the game. It is shown that for the maximally entangled initial state, the classical strategy \\hat{C} (cooperation) becomes the dominant strategy. Our investigation shows that any quantum strategy does no better for any player against the classical strategies. The miracle move of Eisert et al (1999 Phys. Rev. Lett.83 3077) is no more a superior move. We show that the dilemma-like situation is resolved in favor of one player or the other.

Monogamy equalities for qubit entanglement from Lorentz invariance.

PubMed

Eltschka, Christopher; Siewert, Jens

2015-04-10

A striking result from nonrelativistic quantum mechanics is the monogamy of entanglement, which states that a particle can be maximally entangled only with one other party, not with several ones. While there is the exact quantitative relation for three qubits and also several inequalities describing monogamy properties, it is not clear to what extent exact monogamy relations are a general feature of quantum mechanics. We prove that in all many-qubit systems there exist strict monogamy laws for quantum correlations. They come about through the curious relationship between the nonrelativistic quantum mechanics of qubits and Minkowski space. We elucidate the origin of entanglement monogamy from this symmetry perspective and provide recipes to construct new families of such equalities.

Decoherence estimation in quantum theory and beyond

NASA Astrophysics Data System (ADS)

Pfister, Corsin

The quantum physics literature provides many different characterizations of decoherence. Most of them have in common that they describe decoherence as a kind of influence on a quantum system upon interacting with an another system. In the spirit of quantum information theory, we adapt a particular viewpoint on decoherence which describes it as the loss of information into a system that is possibly controlled by an adversary. We use a quantitative framework for decoherence that builds on operational characterizations of the min-entropy that have been developed in the quantum information literature. It characterizes decoherence as an influence on quantum channels that reduces their suitability for a variety of quantifiable tasks such as the distribution of secret cryptographic keys of a certain length or the distribution of a certain number of maximally entangled qubit pairs. This allows for a quantitative and operational characterization of decoherence via operational characterizations of the min-entropy. In this thesis, we present a series of results about the estimation of the minentropy, subdivided into three parts. The first part concerns the estimation of a quantum adversary's uncertainty about classical information--expressed by the smooth min-entropy--as it is done in protocols for quantum key distribution (QKD). We analyze this form of min-entropy estimation in detail and find that some of the more recently suggested QKD protocols have previously unnoticed security loopholes. We show that the specifics of the sifting subroutine of a QKD protocol are crucial for security by pointing out mistakes in the security analysis in the literature and by presenting eavesdropping attacks on those problematic protocols. We provide solutions to the identified problems and present a formalized analysis of the min-entropy estimate that incorporates the sifting stage of QKD protocols. In the second part, we extend ideas from QKD to a protocol that allows to estimate an adversary's uncertainty about quantum information, expressed by the fully quantum smooth min-entropy. Roughly speaking, we show that a protocol that resembles the parallel execution of two QKD protocols can be used to lower bound the min-entropy of some unmeasured qubits. We explain how this result may influence the ongoing search for protocols for entanglement distribution. The third part is dedicated to the development of a framework that allows the estimation of decoherence even in experiments that cannot be correctly described by quantum theory. Inspired by an equivalent formulation of the min-entropy that relates it to the fidelity with a maximally entangled state, we define a decoherence quantity for a very general class of probabilistic theories that reduces to the min-entropy in the special case of quantum theory. This entails a definition of maximal entanglement for generalized probabilistic theories. Using techniques from semidefinite and linear programming, we show how bounds on this quantity can be estimated through Bell-type experiments. This allows to test models for decoherence that cannot be described by quantum theory. As an example application, we devise an experimental test of a model for gravitational decoherence that has been suggested in the literature.

Purcell-enhanced quantum yield from carbon nanotube excitons coupled to plasmonic nanocavities

DOE PAGES

Luo, Yue; Ahmadi, Ehsaneh D.; Shayan, Kamran; ...

2017-11-10

Single-walled carbon nanotubes (SWCNTs) are promising absorbers and emitters to enable novel photonic applications and devices but are also known to suffer from low optical quantum yields. Here we demonstrate SWCNT excitons coupled to plasmonic nanocavity arrays reaching deeply into the Purcell regime with Purcell factors (F P) up to F P = 180 (average F P = 57), Purcell-enhanced quantum yields of 62% (average 42%), and a photon emission rate of 15 MHz into the first lens. The cavity coupling is quasi-deterministic since the photophysical properties of every SWCNT are enhanced by at least one order of magnitude. Furthermore,more » the measured ultra-narrow exciton linewidth (18 ueV) reaches the radiative lifetime limit, which is promising towards generation of transform-limited single photons. Furthermore, to demonstrate utility beyond quantum light sources we show that nanocavity-coupled SWCNTs perform as single-molecule thermometers detecting plasmonically induced heat at cryogenic temperatures in a unique interplay of excitons, phonons, and plasmons at the nanoscale.« less

High-dimensional quantum cloning and applications to quantum hacking

PubMed Central

Bouchard, Frédéric; Fickler, Robert; Boyd, Robert W.; Karimi, Ebrahim

2017-01-01

Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. Although perfect copies are prohibited, a quantum state may be copied with maximal accuracy via various optimal cloning schemes. Optimal quantum cloning, which lies at the border of the physical limit imposed by the no-signaling theorem and the Heisenberg uncertainty principle, has been experimentally realized for low-dimensional photonic states. However, an increase in the dimensionality of quantum systems is greatly beneficial to quantum computation and communication protocols. Nonetheless, no experimental demonstration of optimal cloning machines has hitherto been shown for high-dimensional quantum systems. We perform optimal cloning of high-dimensional photonic states by means of the symmetrization method. We show the universality of our technique by conducting cloning of numerous arbitrary input states and fully characterize our cloning machine by performing quantum state tomography on cloned photons. In addition, a cloning attack on a Bennett and Brassard (BB84) quantum key distribution protocol is experimentally demonstrated to reveal the robustness of high-dimensional states in quantum cryptography. PMID:28168219

High-dimensional quantum cloning and applications to quantum hacking.

PubMed

Bouchard, Frédéric; Fickler, Robert; Boyd, Robert W; Karimi, Ebrahim

2017-02-01

Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. Although perfect copies are prohibited, a quantum state may be copied with maximal accuracy via various optimal cloning schemes. Optimal quantum cloning, which lies at the border of the physical limit imposed by the no-signaling theorem and the Heisenberg uncertainty principle, has been experimentally realized for low-dimensional photonic states. However, an increase in the dimensionality of quantum systems is greatly beneficial to quantum computation and communication protocols. Nonetheless, no experimental demonstration of optimal cloning machines has hitherto been shown for high-dimensional quantum systems. We perform optimal cloning of high-dimensional photonic states by means of the symmetrization method. We show the universality of our technique by conducting cloning of numerous arbitrary input states and fully characterize our cloning machine by performing quantum state tomography on cloned photons. In addition, a cloning attack on a Bennett and Brassard (BB84) quantum key distribution protocol is experimentally demonstrated to reveal the robustness of high-dimensional states in quantum cryptography.

Quantum chi-squared and goodness of fit testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Temme, Kristan; Verstraete, Frank

2015-01-15

A quantum mechanical hypothesis test is presented for the hypothesis that a certain setup produces a given quantum state. Although the classical and the quantum problems are very much related to each other, the quantum problem is much richer due to the additional optimization over the measurement basis. A goodness of fit test for i.i.d quantum states is developed and a max-min characterization for the optimal measurement is introduced. We find the quantum measurement which leads both to the maximal Pitman and Bahadur efficiencies, and determine the associated divergence rates. We discuss the relationship of the quantum goodness of fitmore » test to the problem of estimating multiple parameters from a density matrix. These problems are found to be closely related and we show that the largest error of an optimal strategy, determined by the smallest eigenvalue of the Fisher information matrix, is given by the divergence rate of the goodness of fit test.« less

Entropy bound of local quantum field theory with generalized uncertainty principle

NASA Astrophysics Data System (ADS)

Kim, Yong-Wan; Lee, Hyung Won; Myung, Yun Soo

2009-03-01

We study the entropy bound for local quantum field theory (LQFT) with generalized uncertainty principle. The generalized uncertainty principle provides naturally a UV cutoff to the LQFT as gravity effects. Imposing the non-gravitational collapse condition as the UV-IR relation, we find that the maximal entropy of a bosonic field is limited by the entropy bound A 3 / 4 rather than A with A the boundary area.

Performance improvement of continuous-variable quantum key distribution with an entangled source in the middle via photon subtraction

NASA Astrophysics Data System (ADS)

Guo, Ying; Liao, Qin; Wang, Yijun; Huang, Duan; Huang, Peng; Zeng, Guihua

2017-03-01

A suitable photon-subtraction operation can be exploited to improve the maximal transmission of continuous-variable quantum key distribution (CVQKD) in point-to-point quantum communication. Unfortunately, the photon-subtraction operation faces solving the improvement transmission problem of practical quantum networks, where the entangled source is located in the third part, which may be controlled by a malicious eavesdropper, instead of in one of the trusted parts, controlled by Alice or Bob. In this paper, we show that a solution can come from using a non-Gaussian operation, in particular, the photon-subtraction operation, which provides a method to enhance the performance of entanglement-based (EB) CVQKD. Photon subtraction not only can lengthen the maximal transmission distance by increasing the signal-to-noise rate but also can be easily implemented with existing technologies. Security analysis shows that CVQKD with an entangled source in the middle (ESIM) from applying photon subtraction can well increase the secure transmission distance in both direct and reverse reconciliations of the EB-CVQKD scheme, even if the entangled source originates from an untrusted part. Moreover, it can defend against the inner-source attack, which is a specific attack by an untrusted entangled source in the framework of ESIM.

Random unitary evolution model of quantum Darwinism with pure decoherence

NASA Astrophysics Data System (ADS)

Balanesković, Nenad

2015-10-01

We study the behavior of Quantum Darwinism [W.H. Zurek, Nat. Phys. 5, 181 (2009)] within the iterative, random unitary operations qubit-model of pure decoherence [J. Novotný, G. Alber, I. Jex, New J. Phys. 13, 053052 (2011)]. We conclude that Quantum Darwinism, which describes the quantum mechanical evolution of an open system S from the point of view of its environment E, is not a generic phenomenon, but depends on the specific form of input states and on the type of S-E-interactions. Furthermore, we show that within the random unitary model the concept of Quantum Darwinism enables one to explicitly construct and specify artificial input states of environment E that allow to store information about an open system S of interest with maximal efficiency.

Enhancing teleportation fidelity by means of weak measurements or reversal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiu, Liang, E-mail: lqiu@cumt.edu.cn; Tang, Gang; Yang, Xianqing

2014-11-15

The enhancement of teleportation fidelity by weak measurement or quantum measurement reversal is investigated. One qubit of a maximally entangled state undergoes the amplitude damping, and the subsequent application of weak measurement or quantum measurement reversal could improve the teleportation fidelity beyond the classical region. The improvement could not be attributed to the increasing of entanglement, quantum discord, classical correlation or total correlation. We declare that it should be owed to the probabilistic nature of the method. - Highlights: • The method’s probabilistic nature should be responsible for the improvement. • Quantum or classical correlation cannot explain the improvement. •more » The receiver cannot apply weak measurements. • The sender’s quantum measurement reversal is only useful for |Ψ{sup ±}〉.« less

Optimal quantum networks and one-shot entropies

NASA Astrophysics Data System (ADS)

Chiribella, Giulio; Ebler, Daniel

2016-09-01

We develop a semidefinite programming method for the optimization of quantum networks, including both causal networks and networks with indefinite causal structure. Our method applies to a broad class of performance measures, defined operationally in terms of interative tests set up by a verifier. We show that the optimal performance is equal to a max relative entropy, which quantifies the informativeness of the test. Building on this result, we extend the notion of conditional min-entropy from quantum states to quantum causal networks. The optimization method is illustrated in a number of applications, including the inversion, charge conjugation, and controlization of an unknown unitary dynamics. In the non-causal setting, we show a proof-of-principle application to the maximization of the winning probability in a non-causal quantum game.

Restricted numerical range: A versatile tool in the theory of quantum information

NASA Astrophysics Data System (ADS)

Gawron, Piotr; Puchała, Zbigniew; Miszczak, Jarosław Adam; Skowronek, Łukasz; Życzkowski, Karol

2010-10-01

Numerical range of a Hermitian operator X is defined as the set of all possible expectation values of this observable among a normalized quantum state. We analyze a modification of this definition in which the expectation value is taken among a certain subset of the set of all quantum states. One considers, for instance, the set of real states, the set of product states, separable states, or the set of maximally entangled states. We show exemplary applications of these algebraic tools in the theory of quantum information: analysis of k-positive maps and entanglement witnesses, as well as study of the minimal output entropy of a quantum channel. Product numerical range of a unitary operator is used to solve the problem of local distinguishability of a family of two unitary gates.

Quantum yield and rate constant of the singlet 1Δ g oxygen luminescence in an aqueous medium in the presence of nanoscale inhomogeneities

NASA Astrophysics Data System (ADS)

Jarnikova, E. S.; Parkhats, M. V.; Stasheuski, A. S.; Lepeshkevich, S. V.; Dzhagarov, B. M.

2017-04-01

The quantum yields and lifetimes of photosensitized luminescence of the 1Δ g state of singlet oxygen in an aquatic media with a controlled concentration of dielectric anisotropy centers (polyethylene glycol) have been measured using the methods of laser fluorometry. It is established that the quantum yield and the rate constant ( k r ) of the a 1Δ g → X 3Σ g - luminescence of 1O2 increase as the polymer concentration increases. The effect is analyzed within a general approach involving a relationship between kr and dielectric properties of the medium and is explained by the increased density of photon states and the local field factor in the space around O2( a 1Δ g ).

Accurate quantum yields by laser gain vs absorption spectroscopy - Investigation of Br/Br(asterisk) channels in photofragmentation of Br2 and IBr

NASA Technical Reports Server (NTRS)

Haugen, H. K.; Weitz, E.; Leone, S. R.

1985-01-01

Various techniques have been used to study photodissociation dynamics of the halogens and interhalogens. The quantum yields obtained by these techniques differ widely. The present investigation is concerned with a qualitatively new approach for obtaining highly accurate quantum yields for electronically excited states. This approach makes it possible to obtain an accuracy of 1 percent to 3 percent. It is shown that measurement of the initial transient gain/absorption vs the final absorption in a single time-resolved signal is a very accurate technique in the study of absolute branching fractions in photodissociation. The new technique is found to be insensitive to pulse and probe laser characteristics, molecular absorption cross sections, and absolute precursor density.

Cross sections and quantum yields of the 3 micron emission for Er(3+) and Ho(3+) dopants in crystalsls

NASA Astrophysics Data System (ADS)

Payne, Stephen A.; Smith, Larry K.; Krupke, William F.

1995-05-01

The lifetime, quantum yields, and branching ratios for the 2.8 micron emissions of several Er-and Ho-doped fluorides and oxides were measured. Among the fluoride crystals examined, which included LiYF4, BaY2F8, LaF3, and KY3F10, only the Ho:LiFY4 systems showed any proof of nonradiative decay. Conversely, all the oxide crystals were affected by nonradiative processes, resulting in measured quantum yields ranging from 3.6% for Er:Y3Al5O12 to 62% for Er in Gd3Sc2Ga3O12. In addition, plots of the 2.8 micron emission cross sections for seven Er- and Ho-doped crystals were presented.

Sample-averaged biexciton quantum yield measured by solution-phase photon correlation.

PubMed

Beyler, Andrew P; Bischof, Thomas S; Cui, Jian; Coropceanu, Igor; Harris, Daniel K; Bawendi, Moungi G

2014-12-10

The brightness of nanoscale optical materials such as semiconductor nanocrystals is currently limited in high excitation flux applications by inefficient multiexciton fluorescence. We have devised a solution-phase photon correlation measurement that can conveniently and reliably measure the average biexciton-to-exciton quantum yield ratio of an entire sample without user selection bias. This technique can be used to investigate the multiexciton recombination dynamics of a broad scope of synthetically underdeveloped materials, including those with low exciton quantum yields and poor fluorescence stability. Here, we have applied this method to measure weak biexciton fluorescence in samples of visible-emitting InP/ZnS and InAs/ZnS core/shell nanocrystals, and to demonstrate that a rapid CdS shell growth procedure can markedly increase the biexciton fluorescence of CdSe nanocrystals.

Parity Deformed Jaynes-Cummings Model: “Robust Maximally Entangled States”

PubMed Central

Dehghani, A.; Mojaveri, B.; Shirin, S.; Faseghandis, S. Amiri

2016-01-01

The parity-deformations of the quantum harmonic oscillator are used to describe the generalized Jaynes-Cummings model based on the λ-analog of the Heisenberg algebra. The behavior is interestingly that of a coupled system comprising a two-level atom and a cavity field assisted by a continuous external classical field. The dynamical characters of the system is explored under the influence of the external field. In particular, we analytically study the generation of robust and maximally entangled states formed by a two-level atom trapped in a lossy cavity interacting with an external centrifugal field. We investigate the influence of deformation and detuning parameters on the degree of the quantum entanglement and the atomic population inversion. Under the condition of a linear interaction controlled by an external field, the maximally entangled states may emerge periodically along with time evolution. In the dissipation regime, the entanglement of the parity deformed JCM are preserved more with the increase of the deformation parameter, i.e. the stronger external field induces better degree of entanglement. PMID:27917882

Four-State Continuous-Variable Quantum Key Distribution with Photon Subtraction

NASA Astrophysics Data System (ADS)

Li, Fei; Wang, Yijun; Liao, Qin; Guo, Ying

2018-06-01

Four-state continuous-variable quantum key distribution (CVQKD) is one of the discretely modulated CVQKD which generates four nonorthogonal coherent states and exploits the sign of the measured quadrature of each state to encode information rather than uses the quadrature \\hat {x} or \\hat {p} itself. It has been proven that four-state CVQKD is more suitable than Gaussian modulated CVQKD in terms of transmission distance. In this paper, we propose an improved four-state CVQKD using an non-Gaussian operation, photon subtraction. A suitable photon-subtraction operation can be exploited to improve the maximal transmission of CVQKD in point-to-point quantum communication since it provides a method to enhance the performance of entanglement-based (EB) CVQKD. Photon subtraction not only can lengthen the maximal transmission distance by increasing the signal-to-noise rate but also can be easily implemented with existing technologies. Security analysis shows that the proposed scheme can lengthen the maximum transmission distance. Furthermore, by taking finite-size effect into account we obtain a tighter bound of the secure distance, which is more practical than that obtained in the asymptotic limit.

Violet-to-Blue Gain and Lasing from Colloidal CdS Nanoplatelets: Low-Threshold Stimulated Emission Despite Low Photoluminescence Quantum Yield

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diroll, Benjamin T.; Talapin, Dmitri V.; Schaller, Richard D.

Amplified spontaneous emission (ASE) and lasing from solution-processed materials are demonstrated in the challenging violet-to-blue (430–490 nm) spectral region for colloidal nanoplatelets of CdS and newly synthesized core/shell CdS/ZnS nanoplatelets. Despite modest band-edge photoluminescence quantum yields of 2% or less for single excitons, which we show results from hole trapping, the samples exhibit low ASE thresholds. Furthermore, four-monolayer CdS samples show ASE at shorter wavelengths than any reported film of colloidal quantum-confined material. This work underlines that low quantum yields for single excitons do not necessarily lead to a poor gain medium. The low ASE thresholds originate from negligible dispersionmore » in thickness, large absorption cross sections of 2.8 × 10–14 cm–2, and rather slow (150 to 300 ps) biexciton recombination. We show that under higher-fluence excitation, ASE can kinetically outcompete hole trapping. Using nanoplatelets as the gain medium, lasing is observed in a linear optical cavity. This work confirms the fundamental advantages of colloidal quantum well structures as gain media, even in the absence of high photoluminescence efficiency.« less

Total teleportation of a single-photon state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humble, Travis S; Bennink, Ryan S; Grice, Warren P

2008-01-01

Recent demonstrations of teleportation have transferred quantum information encoded into either polarization or field-quadrature degrees of freedom (DOFs), but an outstanding question is how to simultaneously teleport quantum information encoded into multiple DOFs. We describe how the transverse-spatial, spectral and polarization states of a single photon can be simultaneously teleported using a pair of multimode, polarization-entangled photons derived from spontaneous parametric down-conversion. Furthermore, when the initial photon pair is maximally entangled in the spatial, spectral, and polarization DOFs then the photon s full quantum state can be reliably teleported using a Bell-state measurement based on sum-frequency generation.

Distinguishing computable mixtures of quantum states

NASA Astrophysics Data System (ADS)

Grande, Ignacio H. López; Senno, Gabriel; de la Torre, Gonzalo; Larotonda, Miguel A.; Bendersky, Ariel; Figueira, Santiago; Acín, Antonio

2018-05-01

In this article we extend results from our previous work [Bendersky et al., Phys. Rev. Lett. 116, 230402 (2016), 10.1103/PhysRevLett.116.230402] by providing a protocol to distinguish in finite time and with arbitrarily high success probability any algorithmic mixture of pure states from the maximally mixed state. Moreover, we include an experimental realization, using a modified quantum key distribution setup, where two different random sequences of pure states are prepared; these sequences are indistinguishable according to quantum mechanics, but they become distinguishable when randomness is replaced with pseudorandomness within the experimental preparation process.

Quantum Entanglement and Chemical Reactivity.

PubMed

Molina-Espíritu, M; Esquivel, R O; López-Rosa, S; Dehesa, J S

2015-11-10

The water molecule and a hydrogenic abstraction reaction are used to explore in detail some quantum entanglement features of chemical interest. We illustrate that the energetic and quantum-information approaches are necessary for a full understanding of both the geometry of the quantum probability density of molecular systems and the evolution of a chemical reaction. The energy and entanglement hypersurfaces and contour maps of these two models show different phenomena. The energy ones reveal the well-known stable geometry of the models, whereas the entanglement ones grasp the chemical capability to transform from one state system to a new one. In the water molecule the chemical reactivity is witnessed through quantum entanglement as a local minimum indicating the bond cleavage in the dissociation process of the molecule. Finally, quantum entanglement is also useful as a chemical reactivity descriptor by detecting the transition state along the intrinsic reaction path in the hypersurface of the hydrogenic abstraction reaction corresponding to a maximally entangled state.

Quantum coding with finite resources.

PubMed

Tomamichel, Marco; Berta, Mario; Renes, Joseph M

2016-05-09

The quantum capacity of a memoryless channel determines the maximal rate at which we can communicate reliably over asymptotically many uses of the channel. Here we illustrate that this asymptotic characterization is insufficient in practical scenarios where decoherence severely limits our ability to manipulate large quantum systems in the encoder and decoder. In practical settings, we should instead focus on the optimal trade-off between three parameters: the rate of the code, the size of the quantum devices at the encoder and decoder, and the fidelity of the transmission. We find approximate and exact characterizations of this trade-off for various channels of interest, including dephasing, depolarizing and erasure channels. In each case, the trade-off is parameterized by the capacity and a second channel parameter, the quantum channel dispersion. In the process, we develop several bounds that are valid for general quantum channels and can be computed for small instances.

Continuous variable quantum key distribution with modulated entangled states.

PubMed

Madsen, Lars S; Usenko, Vladyslav C; Lassen, Mikael; Filip, Radim; Andersen, Ulrik L

2012-01-01

Quantum key distribution enables two remote parties to grow a shared key, which they can use for unconditionally secure communication over a certain distance. The maximal distance depends on the loss and the excess noise of the connecting quantum channel. Several quantum key distribution schemes based on coherent states and continuous variable measurements are resilient to high loss in the channel, but are strongly affected by small amounts of channel excess noise. Here we propose and experimentally address a continuous variable quantum key distribution protocol that uses modulated fragile entangled states of light to greatly enhance the robustness to channel noise. We experimentally demonstrate that the resulting quantum key distribution protocol can tolerate more noise than the benchmark set by the ideal continuous variable coherent state protocol. Our scheme represents a very promising avenue for extending the distance for which secure communication is possible.

Quantum coding with finite resources

PubMed Central

Tomamichel, Marco; Berta, Mario; Renes, Joseph M.

2016-01-01

The quantum capacity of a memoryless channel determines the maximal rate at which we can communicate reliably over asymptotically many uses of the channel. Here we illustrate that this asymptotic characterization is insufficient in practical scenarios where decoherence severely limits our ability to manipulate large quantum systems in the encoder and decoder. In practical settings, we should instead focus on the optimal trade-off between three parameters: the rate of the code, the size of the quantum devices at the encoder and decoder, and the fidelity of the transmission. We find approximate and exact characterizations of this trade-off for various channels of interest, including dephasing, depolarizing and erasure channels. In each case, the trade-off is parameterized by the capacity and a second channel parameter, the quantum channel dispersion. In the process, we develop several bounds that are valid for general quantum channels and can be computed for small instances. PMID:27156995

Inkjet printed fluorescent nanorod layers exhibit superior optical performance over quantum dots

NASA Astrophysics Data System (ADS)

Halivni, Shira; Shemesh, Shay; Waiskopf, Nir; Vinetsky, Yelena; Magdassi, Shlomo; Banin, Uri

2015-11-01

Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays.Semiconductor nanocrystals exhibit unique fluorescence properties which are tunable in size, shape and composition. The high quantum yield and enhanced stability have led to their use in biomedical imaging and flat panel displays. Here, semiconductor nanorod based inkjet inks are presented, overcoming limitations of the commonly reported quantum dots in printing applications. Fluorescent seeded nanorods were found to be outstanding candidates for fluorescent inks, due to their low particle-particle interactions and negligible self-absorption. This is manifested by insignificant emission shifts upon printing, even in highly concentrated printed layers and by maintenance of a high fluorescence quantum yield, unlike quantum dots which exhibit fluorescence wavelength shifts and quenching effects. This behavior results from the reduced absorption/emission overlap, accompanied by low energy transfer efficiencies between the nanorods as supported by steady state and time resolved fluorescence measurements. The new seeded nanorod inks enable patterning of thin fluorescent layers, for demanding light emission applications such as signage and displays. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06248a

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Kinetics and quantum yield of photoluminescence of EuFOD3 doped into a nanoporous glass with the help of supercritical CO2

NASA Astrophysics Data System (ADS)

Bagratashvili, V. N.; Gerasimova, V. I.; Gordienko, V. M.; Tsypina, S. I.; Chutko, E. A.

2008-08-01

The kinetics of photoluminescence of a EuFOD3 metalloorganic compound doped into a nanoporous Vycor glass by the method of supercritical fluid impregnation is studied. The lifetime of luminescence of EuFOD3 molecules in pores excited by an excimer XeCl laser was 40 μs, which is considerably smaller than this lifetime (150—890 μs) in solutions. The quantum yield of luminescence of EuFOD3 was estimate as ≈4×10-4.

Quantum Games under Decoherence

NASA Astrophysics Data System (ADS)

Huang, Zhiming; Qiu, Daowen

2016-02-01

Quantum systems are easily influenced by ambient environments. Decoherence is generated by system interaction with external environment. In this paper, we analyse the effects of decoherence on quantum games with Eisert-Wilkens-Lewenstein (EWL) (Eisert et al., Phys. Rev. Lett. 83(15), 3077 1999) and Marinatto-Weber (MW) (Marinatto and Weber, Phys. Lett. A 272, 291 2000) schemes. Firstly, referring to the analytical approach that was introduced by Eisert et al. (Phys. Rev. Lett. 83(15), 3077 1999), we analyse the effects of decoherence on quantum Chicken game by considering different traditional noisy channels. We investigate the Nash equilibria and changes of payoff in specific two-parameter strategy set for maximally entangled initial states. We find that the Nash equilibria are different in different noisy channels. Since Unruh effect produces a decoherence-like effect and can be perceived as a quantum noise channel (Omkar et al., arXiv: 1408.1477v1), with the same two parameter strategy set, we investigate the influences of decoherence generated by the Unruh effect on three-player quantum Prisoners' Dilemma, the non-zero sum symmetric multiplayer quantum game both for unentangled and entangled initial states. We discuss the effect of the acceleration of noninertial frames on the the game's properties such as payoffs, symmetry, Nash equilibrium, Pareto optimal, dominant strategy, etc. Finally, we study the decoherent influences of correlated noise and Unruh effect on quantum Stackelberg duopoly for entangled and unentangled initial states with the depolarizing channel. Our investigations show that under the influence of correlated depolarizing channel and acceleration in noninertial frame, some critical points exist for an unentangled initial state at which firms get equal payoffs and the game becomes a follower advantage game. It is shown that the game is always a leader advantage game for a maximally entangled initial state and there appear some points at which the payoffs become zero.

Separation of photoactive conformers based on hindered diarylethenes: efficient modulation in photocyclization quantum yields.

PubMed

Li, Wenlong; Jiao, Changhong; Li, Xin; Xie, Yongshu; Nakatani, Keitaro; Tian, He; Zhu, Weihong

2014-04-25

Endowing both solvent independency and excellent thermal bistability, the benzobis(thiadiazole)-bridged diarylethene system provides an efficient approach to realize extremely high photocyclization quantum yields (Φo-c , up to 90.6 %) by both separating completely pure anti-parallel conformer and suppressing intramolecular charge transfer (ICT). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photodissociation of quantum state-selected diatomic molecules yields new insight into ultracold chemistry

NASA Astrophysics Data System (ADS)

McDonald, Mickey; McGuyer, Bart H.; Lee, Chih-Hsi; Apfelbeck, Florian; Zelevinsky, Tanya

2016-05-01

When a molecule is subjected to a sufficiently energetic photon it can break apart into fragments through a process called ``photodissociation''. For over 70 years this simple chemical reaction has served as a vital experimental tool for acquiring information about molecular structure, since the character of the photodissociative transition can be inferred by measuring the 3D photofragment angular distribution (PAD). While theoretical understanding of this process has gradually evolved from classical considerations to a fully quantum approach, experiments to date have not yet revealed the full quantum nature of this process. In my talk I will describe recent experiments involving the photodissociation of ultracold, optical lattice-trapped, and fully quantum state-resolved 88Sr2 molecules. Optical absorption images of the PADs produced in these experiments reveal features which are inherently quantum mechanical in nature, such as matter-wave interference between output channels, and are sensitive to the quantum statistics of the molecular wavefunctions. The results of these experiments cannot be predicted using quasiclassical methods. Instead, we describe our results with a fully quantum mechanical model yielding new intuition about ultracold chemistry.

Aqueous synthesis of high bright and tunable near-infrared AgInSe2-ZnSe quantum dots for bioimaging.

PubMed

Che, Dongchen; Zhu, Xiaoxu; Wang, Hongzhi; Duan, Yourong; Zhang, Qinghong; Li, Yaogang

2016-02-01

Efficient synthetic methods for near-infrared quantum dots with good biophysical properties as bioimaging agents are urgently required. In this work, a simple and fast synthesis of highly luminescent, near-infrared AgInSe2-ZnSe quantum dots (QDs) with tunable emissions in aqueous media is reported. This method avoids high temperature and pressure and organic solvents to directly generate water-dispersible AgInSe2-ZnSe QDs. The photoluminescence emission peak of the AgInSe2-ZnSe QDs ranged from 625 to 940nm, with quantum yields up to 31%. The AgInSe2-ZnSe QDs with high quantum yield, near-infrared and low cytotoxic could be used as good cell labels, showing great potential applications in bio-imaging. Copyright © 2015 Elsevier Inc. All rights reserved.

Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

NASA Technical Reports Server (NTRS)

Zhao, Z.; Stickel, R. E.; Wine, P. H.

1995-01-01

Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well-known quantum yield for CO production from 248 nm photolysis of phosgene (Cl2CO2). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S((sup 3)P(sub J)) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S((sup 1)D(sub 2)) + OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N2 + N2O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought.

Culture expansion of adipose derived stromal cells. A closed automated Quantum Cell Expansion System compared with manual flask-based culture.

PubMed

Haack-Sørensen, Mandana; Follin, Bjarke; Juhl, Morten; Brorsen, Sonja K; Søndergaard, Rebekka H; Kastrup, Jens; Ekblond, Annette

2016-11-16

Adipose derived stromal cells (ASCs) are a rich and convenient source of cells for clinical regenerative therapeutic approaches. However, applications of ASCs often require cell expansion to reach the needed dose. In this study, cultivation of ASCs from stromal vascular fraction (SVF) over two passages in the automated and functionally closed Quantum Cell Expansion System (Quantum system) is compared with traditional manual cultivation. Stromal vascular fraction was isolated from abdominal fat, suspended in α-MEM supplemented with 10% Fetal Bovine Serum and seeded into either T75 flasks or a Quantum system that had been coated with cryoprecipitate. The cultivation of ASCs from SVF was performed in 3 ways: flask to flask; flask to Quantum system; and Quantum system to Quantum system. In all cases, quality controls were conducted for sterility, mycoplasmas, and endotoxins, in addition to the assessment of cell counts, viability, immunophenotype, and differentiation potential. The viability of ASCs passage 0 (P0) and P1 was above 96%, regardless of cultivation in flasks or Quantum system. Expression of surface markers and differentiation potential was consistent with ISCT/IFATS standards for the ASC phenotype. Sterility, mycoplasma, and endotoxin tests were consistently negative. An average of 8.0 × 10 7 SVF cells loaded into a Quantum system yielded 8.96 × 10 7 ASCs P0, while 4.5 × 10 6 SVF cells seeded per T75 flask yielded an average of 2.37 × 10 6 ASCs-less than the number of SVF cells seeded. ASCs P1 expanded in the Quantum system demonstrated a population doubling (PD) around 2.2 regardless of whether P0 was previously cultured in flasks or Quantum, while ASCs P1 in flasks only reached a PD of 1.0. Manufacturing of ASCs in a Quantum system enhances ASC expansion rate and yield significantly relative to manual processing in T-flasks, while maintaining the purity and quality essential to safe and robust cell production. Notably, the use of the Quantum system entails significantly reduced working hours and thereby costs.

Analysis of wavelength-dependent photoisomerization quantum yields in bilirubins by fitting two exciton absorption bands

NASA Astrophysics Data System (ADS)

Mazzoni, M.; Agati, G.; Troup, G. J.; Pratesi, R.

2003-09-01

The absorption spectra of bilirubins were deconvoluted by two Gaussian curves of equal width representing the exciton bands of the non-degenerate molecular system. The two bands were used to study the wavelength dependence of the (4Z, 15Z) rightarrow (4Z, 15E) configurational photoisomerization quantum yield of the bichromophoric bilirubin-IXalpha (BR-IX), the intrinsically asymmetric bile pigment associated with jaundice and the symmetrically substituted bilirubins (bilirubin-IIIalpha and mesobilirubin-XIIIalpha), when they are irradiated in aqueous solution bound to human serum albumin (HSA). The same study was performed for BR-IX in ammoniacal methanol solution (NH4OH/MeOH). The quantum yields of the configurational photoprocesses were fitted with a combination function of the two Gaussian bands normalized to the total absorption, using the proportionality coefficients and a scaling factor as parameters. The decrease of the (4Z, 15Z) rightarrow (4Z, 15E) quantum yield with increasing wavelength, which occurs for wavelengths longer than the most probable Franck-Condon transition of the molecule, did not result in a unique function of the exciton absorptions. In particular we found two ranges corresponding to different exciton interactions with different proportionality coefficients and scaling factors. The wavelength-dependent photoisomerization of bilirubins was described as an abrupt change in quantum yield as soon as the resulting excitation was strongly localized in each chromophore. The change was correlated to a variation of the interaction between the two chromophores when the short-wavelength exciton absorption became vanishingly small. With the help of the circular dichroism (CD) spectrum of BR-IX in HSA, a small band was resolved in the bilirubin absorption spectrum, delivering part of the energy required for the (4Z, 15Z) rightarrow (4Z, 15E) photoisomerization of the molecule.

Comparisons of Photosynthetic Responses of Xanthium strumarium and Helianthus annuus to Chronic and Acute Water Stress in Sun and Shade 1

PubMed Central

Ben, Gui-Ying; Osmond, C. Barry; Sharkey, Thomas D.

1987-01-01

We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O2 electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO2 saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O2 per mole photons) was slightly, if at all, affected by mild water stress (>−1.5 megapascals). (c) Severe water stress (<−1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (Fv/Fm) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred. PMID:16665465

Comparisons of Photosynthetic Responses of Xanthium strumarium and Helianthus annuus to Chronic and Acute Water Stress in Sun and Shade.

PubMed

Ben, G Y; Osmond, C B; Sharkey, T D

1987-06-01

We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O(2) electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO(2) saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O(2) per mole photons) was slightly, if at all, affected by mild water stress (>-1.5 megapascals). (c) Severe water stress (<-1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (F(v)/F(m)) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred.

Three-observer Bell inequality violation on a two-qubit entangled state

NASA Astrophysics Data System (ADS)

Schiavon, Matteo; Calderaro, Luca; Pittaluga, Mirko; Vallone, Giuseppe; Villoresi, Paolo

2017-03-01

Bipartite Bell inequalities can simultaneously be violated by two different pairs of observers when weak measurements and signalling is employed. Here, we experimentally demonstrate the violation of two simultaneous CHSH inequalities by exploiting a two-photon polarisation maximally entangled state. Our results demonstrate that large double violation is experimentally achievable. Our demonstration may have impact for Quantum Key Distribution or certification of Quantum Random Number generators based on weak measurements.

Integrability and nonintegrability of quantum systems. II. Dynamics in quantum phase space

NASA Astrophysics Data System (ADS)

Zhang, Wei-Min; Feng, Da Hsuan; Yuan, Jian-Min

1990-12-01

Based on the concepts of integrability and nonintegrability of a quantum system presented in a previous paper [Zhang, Feng, Yuan, and Wang, Phys. Rev. A 40, 438 (1989)], a realization of the dynamics in the quantum phase space is now presented. For a quantum system with dynamical group scrG and in one of its unitary irreducible-representation carrier spaces gerhΛ, the quantum phase space is a 2MΛ-dimensional topological space, where MΛ is the quantum-dynamical degrees of freedom. This quantum phase space is isomorphic to a coset space scrG/scrH via the unitary exponential mapping of the elementary excitation operator subspace of scrg (algebra of scrG), where scrH (⊂scrG) is the maximal stability subgroup of a fixed state in gerhΛ. The phase-space representation of the system is realized on scrG/scrH, and its classical analogy can be obtained naturally. It is also shown that there is consistency between quantum and classical integrability. Finally, a general algorithm for seeking the manifestation of ``quantum chaos'' via the classical analogy is provided. Illustrations of this formulation in several important quantum systems are presented.

Laser flash photolysis of ozone - O/1D/ quantum yields in the fall-off region 297-325 nm

NASA Technical Reports Server (NTRS)

Brock, J. C.; Watson, R. T.

1980-01-01

The wavelength dependence of the quantum yield for O(1D) production from ozone photolysis has been determined between 297.5 nm and 325 nm in order to resolve serious discrepancies among previous studies. The results of this investigation are compared to earlier work by calculating atmospheric production rate constants for O(1D). It is found that for the purpose of calculating this rate constant, there is now good agreement among three studies at 298 K. Furthermore, it appears that previous data on the temperature dependence of the O(1D) quantum yield fall-off is adequate for determining the vertical profile of the O(1D) production rate constant. Several experimental difficulties associated with using NO2(asterisk) chemiluminescence to monitor O(1D) have been identified.

Sample-Averaged Biexciton Quantum Yield Measured by Solution-Phase Photon Correlation

DOE PAGES

Beyler, Andrew P.; Bischof, Thomas S.; Cui, Jian; ...

2014-11-19

The brightness of nanoscale optical materials such as semiconductor nanocrystals is currently limited in high excitation flux applications by inefficient multiexciton fluorescence. We have devised a solution-phase photon correlation measurement that can conveniently and reliably measure the average biexciton-to-exciton quantum yield ratio of an entire sample without user selection bias. This technique can be used to investigate the multiexciton recombination dynamics of a broad scope of synthetically underdeveloped materials, including those with low exciton quantum yields and poor fluorescence stability. Here in this study, we have applied this method to measure weak biexciton fluorescence in samples of visible-emitting InP/ZnS andmore » InAs/ZnS core/shell nanocrystals, and to demonstrate that a rapid CdS shell growth procedure can markedly increase the biexciton fluorescence of CdSe nanocrystals.« less

Quantitative photoabsorption and fluorescence spectroscopy of benzene, naphthalene, and some derivatives at 106-295 nm

NASA Technical Reports Server (NTRS)

Suto, Masako; Wang, Xiuyan; Shan, Jun; Lee, L. C.

1992-01-01

Photoabsorption and fluorescence cross sections of benzene, (o-, m-, p-) xylenes, naphthalene, 1-methylnaphthalene, and 2-ethylnaphthalene in the gas phase are measured at 106-295 nm using synchrotron radiation as a light source. Fluorescences are observed from the photoexcitation of benzene and xylenes at 230-280 nm and from naphthalene and its derivatives at 190-295 nm. The absolute fluorescence cross section is determined by calibration with respect to the emission intensity of the NO(A-X) system, for which the fluorescence quantum yield is equal to 1. To cross-check the current calibration method, the quantum yield of the SO2(C-X) system at 220-230 nm was measured since it is about equal to 1. The current quantum-yield data are compared with previously published values measured by different methods.

Sample-Averaged Biexciton Quantum Yield Measured by Solution-Phase Photon Correlation

PubMed Central

Beyler, Andrew P.; Bischof, Thomas S.; Cui, Jian; Coropceanu, Igor; Harris, Daniel K.; Bawendi, Moungi G.

2015-01-01

The brightness of nanoscale optical materials such as semiconductor nanocrystals is currently limited in high excitation flux applications by inefficient multiexciton fluorescence. We have devised a solution-phase photon correlation measurement that can conveniently and reliably measure the average biexciton-to-exciton quantum yield ratio of an entire sample without user selection bias. This technique can be used to investigate the multiexciton recombination dynamics of a broad scope of synthetically underdeveloped materials, including those with low exciton quantum yields and poor fluorescence stability. Here, we have applied this method to measure weak biexciton fluorescence in samples of visible-emitting InP/ZnS and InAs/ZnS core/shell nanocrystals, and to demonstrate that a rapid CdS shell growth procedure can markedly increase the biexciton fluorescence of CdSe nanocrystals. PMID:25409496

No-cloning of quantum steering

NASA Astrophysics Data System (ADS)

Chiu, Ching-Yi; Lambert, Neill; Liao, Teh-Lu; Nori, Franco; Li, Che-Ming

2016-06-01

Einstein-Podolsky-Rosen (EPR) steering allows two parties to verify their entanglement, even if one party’s measurements are untrusted. This concept has not only provided new insights into the nature of non-local spatial correlations in quantum mechanics, but also serves as a resource for one-sided device-independent quantum information tasks. Here, we investigate how EPR steering behaves when one-half of a maximally entangled pair of qudits (multidimensional quantum systems) is cloned by a universal cloning machine. We find that EPR steering, as verified by a criterion based on the mutual information between qudits, can only be found in one of the copy subsystems but not both. We prove that this is also true for the single-system analogue of EPR steering. We find that this restriction, which we term ‘no-cloning of quantum steering’, elucidates the physical reason why steering can be used to secure sources and channels against cloning-based attacks when implementing quantum communication and quantum computation protocols.

Transmission of photonic quantum polarization entanglement in a nanoscale hybrid plasmonic waveguide.

PubMed

Li, Ming; Zou, Chang-Ling; Ren, Xi-Feng; Xiong, Xiao; Cai, Yong-Jing; Guo, Guo-Ping; Tong, Li-Min; Guo, Guang-Can

2015-04-08

Photonic quantum technologies have been extensively studied in quantum information science, owing to the high-speed transmission and outstanding low-noise properties of photons. However, applications based on photonic entanglement are restricted due to the diffraction limit. In this work, we demonstrate for the first time the maintaining of quantum polarization entanglement in a nanoscale hybrid plasmonic waveguide composed of a fiber taper and a silver nanowire. The transmitted state throughout the waveguide has a fidelity of 0.932 with the maximally polarization entangled state Φ(+). Furthermore, the Clauser, Horne, Shimony, and Holt (CHSH) inequality test performed, resulting in value of 2.495 ± 0.147 > 2, demonstrates the violation of the hidden variable model. Because the plasmonic waveguide confines the effective mode area to subwavelength scale, it can bridge nanophotonics and quantum optics and may be used as near-field quantum probe in a quantum near-field micro/nanoscope, which can realize high spatial resolution, ultrasensitive, fiber-integrated, and plasmon-enhanced detection.

More nonlocality with less purity.

PubMed

Bandyopadhyay, Somshubhro

2011-05-27

Quantum information is nonlocal in the sense that local measurements on a composite quantum system, prepared in one of many mutually orthogonal states, may not reveal in which state the system was prepared. It is shown that in the many copy limit this kind of nonlocality is fundamentally different for pure and mixed quantum states. In particular, orthogonal mixed states may not be distinguishable by local operations and classical communication, no matter how many copies are supplied, whereas any set of N orthogonal pure states can be perfectly discriminated with m copies, where m

Deterministic error correction for nonlocal spatial-polarization hyperentanglement

PubMed Central

Li, Tao; Wang, Guan-Yu; Deng, Fu-Guo; Long, Gui-Lu

2016-01-01

Hyperentanglement is an effective quantum source for quantum communication network due to its high capacity, low loss rate, and its unusual character in teleportation of quantum particle fully. Here we present a deterministic error-correction scheme for nonlocal spatial-polarization hyperentangled photon pairs over collective-noise channels. In our scheme, the spatial-polarization hyperentanglement is first encoded into a spatial-defined time-bin entanglement with identical polarization before it is transmitted over collective-noise channels, which leads to the error rejection of the spatial entanglement during the transmission. The polarization noise affecting the polarization entanglement can be corrected with a proper one-step decoding procedure. The two parties in quantum communication can, in principle, obtain a nonlocal maximally entangled spatial-polarization hyperentanglement in a deterministic way, which makes our protocol more convenient than others in long-distance quantum communication. PMID:26861681

Deterministic error correction for nonlocal spatial-polarization hyperentanglement.

PubMed

Li, Tao; Wang, Guan-Yu; Deng, Fu-Guo; Long, Gui-Lu

2016-02-10

Hyperentanglement is an effective quantum source for quantum communication network due to its high capacity, low loss rate, and its unusual character in teleportation of quantum particle fully. Here we present a deterministic error-correction scheme for nonlocal spatial-polarization hyperentangled photon pairs over collective-noise channels. In our scheme, the spatial-polarization hyperentanglement is first encoded into a spatial-defined time-bin entanglement with identical polarization before it is transmitted over collective-noise channels, which leads to the error rejection of the spatial entanglement during the transmission. The polarization noise affecting the polarization entanglement can be corrected with a proper one-step decoding procedure. The two parties in quantum communication can, in principle, obtain a nonlocal maximally entangled spatial-polarization hyperentanglement in a deterministic way, which makes our protocol more convenient than others in long-distance quantum communication.

Paraheliotropism can protect water-stressed bean (Phaseolus vulgaris L.) plants against photoinhibition.

PubMed

Pastenes, Claudio; Porter, Victor; Baginsky, Cecilia; Horton, Peter; González, Javiera

2004-12-01

In order to estimate the importance of leaf movements on photosynthesis in well-watered and water-stressed field grown bean cultivars (Arroz Tuscola (AT), Orfeo INIA (OI), Bayos Titan (BT), and Hallados Dorado (HD)), CO2 assimilation, leaf temperature, and capacity for the maximum quantum yield recovery, measured as Fv/Fm, were assessed. Leaf water potential was lower in water-stressed compared to control plants throughout the day. Water status determined a decrease in the CO2 assimilation and stomatal conductance as light intensity and temperature increased up to maximal intensities at midday. Both parameters were lower in stressed compared to control plants. Even though high light intensity and water-stress induced stomatal closure is regarded as a photoinhibitory condition, the recovery of variable to maximal fluorescence (Fv/Fm) after 30min of darkness was nearly constant in both water regimes. In fact, higher values were observed in OI and AT when under stress. Photochemical and non-photochemical fluorescence quenching resulted in minor changes during the day and were similar between watered and stressed plants. It is concluded that paraheliotropism, present in the four bean cultivars, efficiently protects stressed plants from photoinhibition in the field and helps maintain leaf temperatures far below the ambient temperatures, however, it may also be responsible for low CO2 assimilation rates in watered plants.

Theory of single-photon detectors employing smart strategies of detection

NASA Astrophysics Data System (ADS)

Silva, João Batista Rosa; Ramos, Rubens Viana

2005-11-01

Single-photon detectors have become more important with the advent of set-ups for optical communication using single-photon pulses, mainly quantum key distribution. The performance of quantum key distribution systems depends strongly on the performance of single-photon detectors. In this paper, aiming to overcome the afterpulsing that limits strongly the maximal transmission rate of quantum key distribution systems, three smart strategies for single-photon detection are discussed using analytical and numerical procedures. The three strategies are: hold-off time conditioned to avalanche presence, termed the Norwegian strategy, using one avalanche photodiode, using two raffled avalanche photodiodes and using two switched avalanche photodiodes. Finally we give examples using these strategies in a quantum key distribution set-up.

Rigidity of the magic pentagram game

NASA Astrophysics Data System (ADS)

Kalev, Amir; Miller, Carl A.

2018-01-01

A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for multiple classes of games. In this paper we prove ridigity for the magic pentagram game, a simple binary constraint satisfaction game involving two players, five clauses and ten variables. We show that all near-optimal strategies for the pentagram game are approximately equivalent to a unique strategy involving real Pauli measurements on three maximally-entangled qubit pairs.

Rigidity of the magic pentagram game.

PubMed

Kalev, Amir; Miller, Carl A

2018-01-01

A game is rigid if a near-optimal score guarantees, under the sole assumption of the validity of quantum mechanics, that the players are using an approximately unique quantum strategy. Rigidity has a vital role in quantum cryptography as it permits a strictly classical user to trust behavior in the quantum realm. This property can be traced back as far as 1998 (Mayers and Yao) and has been proved for multiple classes of games. In this paper we prove ridigity for the magic pentagram game, a simple binary constraint satisfaction game involving two players, five clauses and ten variables. We show that all near-optimal strategies for the pentagram game are approximately equivalent to a unique strategy involving real Pauli measurements on three maximally-entangled qubit pairs.

Effects of Initial Correlation and Quantum Coherence on the Energy Transfer, Purity and Entanglement

NASA Astrophysics Data System (ADS)

Meng, Xiangjia; Chen, Longxi

2018-04-01

We investigate the influences of the initial correlation and quantum coherence on a bipartite dissipative system which is modeled by two two-level quantum emitters driven by an external laser field. It is shown that the initial correlation can enhance or suppress the dynamical evolution of the energy transfer quantified by the excited-state population and the information flow between the two emitters characterized by the purity. We also present the degree of the influence of the initial correlation that is determined by the quantum coherence induced by a relative phase. By introducing Bloch sphere, we illustrate the relation between the energy transfer and the purity. In addition, a scheme for generating maximally entangled steady state is proposed.

Quantum interference of position and momentum: A particle propagation paradox

NASA Astrophysics Data System (ADS)

Hofmann, Holger F.

2017-08-01

Optimal simultaneous control of position and momentum can be achieved by maximizing the probabilities of finding their experimentally observed values within two well-defined intervals. The assumption that particles move along straight lines in free space can then be tested by deriving a lower limit for the probability of finding the particle in a corresponding spatial interval at any intermediate time t . Here, it is shown that this lower limit can be violated by quantum superpositions of states confined within the respective position and momentum intervals. These violations of the particle propagation inequality show that quantum mechanics changes the laws of motion at a fundamental level, providing a different perspective on causality relations and time evolution in quantum mechanics.

Efficiency at maximum power of a laser quantum heat engine enhanced by noise-induced coherence

NASA Astrophysics Data System (ADS)

Dorfman, Konstantin E.; Xu, Dazhi; Cao, Jianshu

2018-04-01

Quantum coherence has been demonstrated in various systems including organic solar cells and solid state devices. In this article, we report the lower and upper bounds for the performance of quantum heat engines determined by the efficiency at maximum power. Our prediction based on the canonical three-level Scovil and Schulz-Dubois maser model strongly depends on the ratio of system-bath couplings for the hot and cold baths and recovers the theoretical bounds established previously for the Carnot engine. Further, introducing a fourth level to the maser model can enhance the maximal power and its efficiency, thus demonstrating the importance of quantum coherence in the thermodynamics and operation of the heat engines beyond the classical limit.

A Phosphine-Free Route to Size-Adjustable CdSe and CdSe/CdS Core-Shell Quantum Dots for White-Light-Emitting Diodes.

PubMed

Zhang, Yugang; Li, Guopeng; Zhang, Ting; Song, Zihang; Wang, Hui; Zhang, Zhongping; Jiang, Yang

2018-03-01

The selenium dioxide was used as the precursor to synthesize wide-size-ranged CdSe quantum dots (2.4-5.7 nm) via hot-injection route. The CdSe quantum dots are featured with high crystalline, monodisperse, zinc blende structure and wide emission region (530-635 nm). In order to improve the stability and quantum yield, a phosphine-free single-molecular precursor approach is used to obtain CdSe/CdS core/shell quantum dots. The CdSe/CdS quantum dots are highly fluorescent with quantum yield up to 65%, and persist the good monodispersity and high crystallinity. Moreover, the quantum dots white light-emitting-diodes are fabricated by using the resultant red emission core/shell quantum dots and Y3Al5O12:Ce3+ yellow phosphors as color-conversion layers on a blue InGaN chip. The prepared light-emitting-diodes show good performance with CIE-1931 coordinated of (0.3583, 0.3349), an Ra of 92.9, and a Tc of 4410 K at 20 mA, which indicate that the combination of red-emission QDs and yellow phophors as a promising approach to obtain warm WLEDs with good color rendering.

Physiological responses to copper in giant clams: a comparison of two methods in revealing effects on photosynthesis in zooxanthellae.

PubMed

Elfwing, Tina; Blidberg, Eva; Tedengren, Michael

2002-08-01

In the present work physiological responses to a short term, sub-lethal exposure to copper (5 microg Cu2 l(-1) were studied on two species of giant clams, Tridacna gigas and Hippopus hippopus. All giant clams (fam. Tridacnidae) maintain a symbiotic relationship with photo-synthesising microalgae (zooxanthellae) and the phytotoxic effects of this copper concentration were approached with two different end points: changes in oxygen production and maximal quantum yield (Fv/Fm). Additionally we measured respiration, whereby Pg:R ratios could be calculated for the system (algae and clam) and used as an indicator of stress. Cu accumulation was only determined for T. gigas and showed significantly higher tissue concentrations in exposed specimens (11.3 microg Cu g(-1) dry wt) compared to the controls (4.2 microg Cu g(-1)). Both species displayed significantly reduced Pg:R ratios due to exposure, mainly explained by lowered gross production. No indication of stress was shown in the fluorescence measurements and possible explanations are discussed in the paper. We propose that inhibitions in the slow kinetics of photosynthesis were not captured by this fluorescence parameter. Accordingly we suggest that measurements of maximum fluorescence yield should be accompanied by complementary parameters when studying pollutants with unclear phytotoxic mechanisms.

Excited-state properties of nucleic acid components

NASA Astrophysics Data System (ADS)

Salet, C.; Bensasson, R. V.; Becker, R. S.

1981-12-01

Measurements were made of the fluorescence and phosphorescence spectra and lifetimes, and also of the absorption spectra, lifetimes, extinction coefficients, and quantum yields of the T1 lower triplet states of thymine, uracil, their N, N'-dimethyl derivatives, thymidine, thymidine monophosphate, uridine, and uridine monophosphate in various solvents at 300 °K. The influence of the solvent on the quantum yield of the T1 state of nucleic acid components is discussed.

Laboratory Measurements of Photolytic Parameters for Formaldehyde.

DTIC Science & Technology

1980-11-01

dynamic dilution methods. Compressed air stored in steel cylinders, carefully selected to contain carbon monoxide and hydrogen at mixing ratios of...in air has been investi- gated in the laboratory at two temperatures: 300 and 220 K. Quantum yields for the formation of CO and H2 were determined at...procedures in the case of pure formaldehyde gave consistent results. (b) Quantum Yields Mixtures of formaldehyde in air were photolyzed in a

Synthesis and characterization of near-infrared absorbing water soluble squaraines and study of their photodynamic effects in DLA live cells.

PubMed

Shafeekh, Kulathinte M; Soumya, Mohanannair S; Rahim, Moochikkadavath A; Abraham, Annie; Das, Suresh

2014-01-01

Here, we report the synthesis, photophysical properties and photodynamic effects in DLA live cells of three water soluble squaraine dyes, viz. bisbenzothiazolium squaraine dyes SQMI and SQDI with iodine in one and both benzothiazolium units, respectively, and an unsymmetrical squaraine dye ASQI containing iodinated benzothiazolium and aniline substituents. The diiodinated SQDI showed an anomalous trend in both fluorescence and triplet quantum yields over the monoiodinated SQMI, with SQDI showing higher fluorescence and lower triplet quantum yields compared to SQMI. Nanosecond laser flash photolysis of SQDI and SQMI indicated the formation of triplet excited states with quantum yield of 0.19 and 0.26, respectively. On photoirradiation, both the SQDI and SQMI generate singlet oxygen and it was observed that both dyes undergoing oxidation reactions with the singlet oxygen generated. ASQI which exhibited a lower triplet quantum yield of 0.06 was, however, stable and did not react with the singlet oxygen generated. In vitro cytotoxicity studies of these dyes in DLA live cells were performed using Trypan blue dye exclusion method and it reflect an order of cytotoxicity of SQDI>SQMI>ASQI. Intracellular generation of the ROS was confirmed by dichlorofluorescein assay after the in vitro PDT. © 2014 The American Society of Photobiology.

Efficiencies of induction of DNA double strand breaks in solution by photoabsorption at phosphorus and platinum.

PubMed

Maeda, Munetoshi; Kobayashi, Katsumi; Hieda, Kotaro

2004-01-01

This paper aims at determining and comparing the cross sections and quantum yields for DNA strand break induction by the Auger effect at the K-shell of phosphorus and at the LIII-shell of platinum. Using synchrotron radiation, free and Pt-bound pBR322 plasmid DNA were irradiated in solution with monochromatic X-rays, the energies of which were 2.153 and 2.147 keV, corresponding to "on" and "below" the phosphorus K-shell photoabsorption, and 11.566 and 11.542 keV for "above" and "below" the L(III)-shell photoabsorption of platinum, respectively. To suppress indirect effects by hydroxyl radicals, DMSO (1M) was used as a scavenger. The inner-shell photoabsorption of phosphorus and of platinum significantly increased the induction of DNA double strand breaks (DSB), whereas it had little effect on single strand break (SSB) induction. The quantum yields for the induction of DSB were calculated to be 0.017 and 1.13, in the case of phosphorus and platinum, respectively. CONCLSIONS: The value of the quantum yield for the DSB induction of platinum was about 66-fold larger than that for the phosphorus. These results clearly demonstrate that the quantum yield of DSB depends upon the magnitude of the Auger cascade.

Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst.

PubMed

Gao, Honglin; Yan, Shicheng; Wang, Jiajia; Huang, Yu An; Wang, Peng; Li, Zhaosheng; Zou, Zhigang

2013-11-07

The development of efficient photocatalytic material for converting solar energy to hydrogen energy as viable alternatives to fossil-fuel technologies is expected to revolutionize energy shortage and environment issues. However, to date, the low quantum yield for solar hydrogen production over photocatalysts has hindered advances in the practical applications of photocatalysis. Here, we show that a carbon nitride intercalation compound (CNIC) synthesized by a simple molten salt route is an efficient polymer photocatalyst with a high quantum yield. We found that coordinating the alkali metals into the C-N plane of carbon nitride will induce the un-uniform spatial charge distribution. The electrons are confined in the intercalated region while the holes are in the far intercalated region, which promoted efficient separation of photogenerated carriers. The donor-type alkali metal ions coordinating into the nitrogen pots of carbon nitrides increase the free carrier concentration and lead to the formation of novel nonradiative paths. This should favor improved transport of the photogenerated electron and hole and decrease the electron-hole recombination rate. As a result, the CNIC exhibits a quantum yield as high as 21.2% under 420 nm light irradiation for solar hydrogen production. Such high quantum yield opens up new opportunities for using cheap semiconducting polymers as energy transducers.

Intense visible emission from ZnO/PAAX (X = H or Na) nanocomposite synthesized via a simple and scalable sol-gel method

NASA Astrophysics Data System (ADS)

Zhu, Y.; Apostoluk, A.; Gautier, P.; Valette, A.; Omar, L.; Cornier, T.; Bluet, J. M.; Masenelli-Varlot, K.; Daniele, S.; Masenelli, B.

2016-03-01

Intense visible nano-emitters are key objects for many technologies such as single photon source, bio-labels or energy convertors. Chalcogenide nanocrystals have ruled this domain for several decades. However, there is a demand for cheaper and less toxic materials. In this scheme, ZnO nanoparticles have appeared as potential candidates. At the nanoscale, they exhibit crystalline defects which can generate intense visible emission. However, even though photoluminescence quantum yields as high as 60% have been reported, it still remains to get quantum yield of that order of magnitude which remains stable over a long period. In this purpose, we present hybrid ZnO/polyacrylic acid (PAAH) nanocomposites, obtained from the hydrolysis of diethylzinc in presence of PAAH, exhibiting quantum yield systematically larger than 20%. By optimizing the nature and properties of the polymeric acid, the quantum yield is increased up to 70% and remains stable over months. This enhancement is explained by a model based on the hybrid type II heterostructure formed by ZnO/PAAH. The addition of PAAX (X = H or Na) during the hydrolysis of ZnEt2 represents a cost effective method to synthesize scalable amounts of highly luminescent ZnO/PAAX nanocomposites.

Faster search by lackadaisical quantum walk

NASA Astrophysics Data System (ADS)

Wong, Thomas G.

2018-03-01

In the typical model, a discrete-time coined quantum walk searching the 2D grid for a marked vertex achieves a success probability of O(1/log N) in O(√{N log N}) steps, which with amplitude amplification yields an overall runtime of O(√{N} log N). We show that making the quantum walk lackadaisical or lazy by adding a self-loop of weight 4 / N to each vertex speeds up the search, causing the success probability to reach a constant near 1 in O(√{N log N}) steps, thus yielding an O(√{log N}) improvement over the typical, loopless algorithm. This improved runtime matches the best known quantum algorithms for this search problem. Our results are based on numerical simulations since the algorithm is not an instance of the abstract search algorithm.

Efficiency enhancement of hybridized solar cells through co-sensitization and fast charge extraction by up-converted polyethylene glycol modified carbon quantum dots

NASA Astrophysics Data System (ADS)

Zhu, Wanlu; Duan, Jialong; Duan, Yanyan; Zhao, Yuanyuan; Tang, Qunwei

2017-11-01

Photovoltaics are promising solutions to energy crisis and environmental pollution problems. The dye-sensitized solar cells with mesoscopic structures have attracted growing interests because of zero emissions, easy fabrication, scalable materials and techniques, etc. However, the state-of-the-art dye-sensitized solar cells have narrow spectral absorption for photoelectric conversion and high electron-hole recombination rate under sunlight illumination. Therefore, it is a persistent object to make wide-spectral absorption and fast charge extraction solar cells for energy harvest in both solar and dark-light conditions. To address this issue, we present here experimental realization of a category of solar cells converting visible and near-infrared light into electricity by co-sensitizing photoanode with N719 dye and polyethylene glycol (PEG) modified carbon quantum dots (PEG-m-CQDs), arising from up-conversion and hole-transporting behaviors of PEG-m-CQDs as well as photofluorescence of green-emitting long persistence phosphors. The optimized solar cell yields maximized photoelectric conversion efficiencies of 9.89% and 25.81% under simulated sunlight (air mass 1.5, 100 mW cm-2) illumination and dark conditions, respectively. This work is far from optimization, but the physical proof-of-concept hybridized solar cell may markedly increase electricity generation time and total power output of photovoltaic platforms.

Microscopic heat engine and control of work fluctuations

NASA Astrophysics Data System (ADS)

Xiao, Gaoyang

In this thesis, we study novel behaviors of microscopic work and heat in systems involving few degrees of freedom. We firstly report that a quantum Carnot cycle should consist of two isothermal processes and two mechanical adiabatic processes if we want to maximize its heat-to-work conversion efficiency. We then find that the efficiency can be further optimized, and it is generally system specific, lower than the Carnot efficiency, and dependent upon both temperatures of the cold and hot reservoirs. We then move on to the studies the fluctuations of microscopic work. We find a principle of minimal work fluctuations related to the Jarzynski equality. In brief, an adiabatic process without energy level crossing yields the minimal fluctuations in exponential work, given a thermally isolated system initially prepared at thermal equilibrium. Finally, we investigate an optimal control approach to suppress the work fluctuations and accelerate the adiabatic processes. This optimal control approach can apply to wide variety of systems even when we do not have full knowledge of the systems.

Live event reconstruction in an optically read out GEM-based TPC

NASA Astrophysics Data System (ADS)

Brunbauer, F. M.; Galgóczi, G.; Gonzalez Diaz, D.; Oliveri, E.; Resnati, F.; Ropelewski, L.; Streli, C.; Thuiner, P.; van Stenis, M.

2018-04-01

Combining strong signal amplification made possible by Gaseous Electron Multipliers (GEMs) with the high spatial resolution provided by optical readout, highly performing radiation detectors can be realized. An optically read out GEM-based Time Projection Chamber (TPC) is presented. The device permits 3D track reconstruction by combining the 2D projections obtained with a CCD camera with timing information from a photomultiplier tube. Owing to the intuitive 2D representation of the tracks in the images and to automated control, data acquisition and event reconstruction algorithms, the optically read out TPC permits live display of reconstructed tracks in three dimensions. An Ar/CF4 (80/20%) gas mixture was used to maximize scintillation yield in the visible wavelength region matching the quantum efficiency of the camera. The device is integrated in a UHV-grade vessel allowing for precise control of the gas composition and purity. Long term studies in sealed mode operation revealed a minor decrease in the scintillation light intensity.

Geometric phase in entangled systems: A single-neutron interferometer experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sponar, S.; Klepp, J.; Loidl, R.

2010-04-15

The influence of the geometric phase on a Bell measurement, as proposed by Bertlmann et al. [Phys. Rev. A 69, 032112 (2004)] and expressed by the Clauser-Horne-Shimony-Holt (CHSH) inequality, has been observed for a spin-path-entangled neutron state in an interferometric setup. It is experimentally demonstrated that the effect of geometric phase can be balanced by a change in Bell angles. The geometric phase is acquired during a time-dependent interaction with a radiofrequency field. Two schemes, polar and azimuthal adjustment of the Bell angles, are realized and analyzed in detail. The former scheme yields a sinusoidal oscillation of the correlation functionmore » S, dependent on the geometric phase, such that it varies in the range between 2 and 2{radical}(2) and therefore always exceeds the boundary value 2 between quantum mechanic and noncontextual theories. The latter scheme results in a constant, maximal violation of the Bell-like CHSH inequality, where S remains 2{radical}(2) for all settings of the geometric phase.« less

The effects of lead stress on photosynthetic function and chloroplast ultrastructure of Robinia pseudoacacia seedlings.

PubMed

Zhou, Jian; Jiang, Zeping; Ma, Jie; Yang, Lifeng; Wei, Yuan

2017-04-01

In this experiment, the effects of different lead (Pb) concentrations (0, 200, 600, 1000, 1400 mg kg -1 ) on photosynthesis and chlorophyll fluorescence in Robinia pseudoacacia seedlings were examined. As Pb concentration increased, chlorophyll a, chlorophyll b, total chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance (g s ), and mesophyll intercellular carbon dioxide concentration were gradually reduced. Maximal photochemical efficiency, photochemical quenching, and quantum yield also decreased. However, the initial fluorescence and nonphotochemical quenching gradually increased. Chloroplasts swelled owing to local plasmolysis and lost most of their starch content, and their thylakoid lamellae gradually became disordered and loosely packed. When the chloroplast envelope was lost under high Pb stress (≥1000 mg kg -1 ), lipid globules were released into the surrounding mesophyll cell. Multiple regression analysis showed that g s and inactivity of the PSII reaction center had the greatest effect on photosynthetic function, whereas inhibition of electron transport had minimal effects on black locust seedlings under Pb stress.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orfield, Noah J.; McBride, James R.; Wang, Feng

Physical variations in colloidal nanostructures give rise to heterogeneity in expressed optical behavior. This correlation between nanoscale structure and function demands interrogation of both atomic structure and photophysics at the level of single nanostructures to be fully understood. In this paper, by conducting detailed analyses of fine atomic structure, chemical composition, and time-resolved single-photon photoluminescence data for the same individual nanocrystals, we reveal inhomogeneity in the quantum yields of single nonblinking “giant” CdSe/CdS core/shell quantum dots (g-QDs). We find that each g-QD possesses distinctive single exciton and biexciton quantum yields that result mainly from variations in the degree of charging,more » rather than from volume or structure inhomogeneity. We further establish that there is a very limited nonemissive “dark” fraction (<2%) among the studied g-QDs and present direct evidence that the g-QD core must lack inorganic passivation for the g-QD to be “dark”. Finally and therefore, in contrast to conventional QDs, ensemble photoluminescence quantum yield is principally defined by charging processes rather than the existence of dark g-QDs.« less

Entangled Dynamics in Macroscopic Quantum Tunneling of Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Alcala, Diego A.; Glick, Joseph A.; Carr, Lincoln D.

2017-05-01

Tunneling of a quasibound state is a nonsmooth process in the entangled many-body case. Using time-evolving block decimation, we show that repulsive (attractive) interactions speed up (slow down) tunneling. While the escape time scales exponentially with small interactions, the maximization time of the von Neumann entanglement entropy between the remaining quasibound and escaped atoms scales quadratically. Stronger interactions require higher-order corrections. Entanglement entropy is maximized when about half the atoms have escaped.

Strongly Coupled Tin-Halide Perovskites to Modulate Light Emission: Tunable 550-640 nm Light Emission (FWHM 36-80 nm) with a Quantum Yield of up to 6.4.

PubMed

Chen, Min-Yi; Lin, Jin-Tai; Hsu, Chia-Shuo; Chang, Chung-Kai; Chiu, Ching-Wen; Chen, Hao Ming; Chou, Pi-Tai

2018-05-01

Colloidal perovskite quantum dots represent one of the most promising materials for applications in solar cells and photoluminescences. These devices require a low density of crystal defects and a high yield of photogenerated carriers, which are difficult to realize in tin-halide perovskite because of the intrinsic instability of tin during nucleation. Here, an enhancement in the luminescent property of tin-halide perovskite nanoplates (TPNPs) that are composed of strongly coupled layered structures with the chemical formula of PEA 2 SnX 4 (PEA = C 6 H 5 (CH 2 ) 2 NH 3 , X = Br, I) is reported. TPNPs (X = I) show an emission at a wavelength of 640 nm, with high quantum yield of 6.40 ± 0.14% and full width at half maximum (FWHM) as small as 36 nm. The presence of aliphatic carboxylic acid is found to play a key role in reducing the tin perovskite defect density, which significantly improves the emission intensity and stability of TPNPs. Upon mixing iodo- and bromo- precursors, the emission wavelength is successfully tuned from 640 nm (PEA 2 SnI 4 ) to 550 nm (PEA 2 SnBr 4 ), with a corresponding emission quantum yield and FWHM of 0.16-6.40% and 36-80 nm, respectively. The results demonstrate a major advance for the emission yield and tunability of tin-halide perovskites. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoswitchable Fluorescent Diarylethene Derivatives with Thiophene 1,1-Dioxide Groups: Effect of Alkyl Substituents at the Reactive Carbons

PubMed Central

Sumi, Takaki; Irie, Masahiro

2017-01-01

Photoswitching and fluorescent properties of sulfone derivatives of 1,2-bis(2-alkyl-4-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, 1–5, having methyl, ethyl, n-propyl, i-propyl, and i-butyl substituents at the reactive carbons (2- and 2′-positions) of the thiophene 1,1-dioxide rings were studied. Diarylethenes 1–5 underwent isomerization reactions between open-ring and closed-ring forms upon alternate irradiation with ultraviolet (UV) and visible light and showed fluorescence in the closed-ring forms. The alkyl substitution at the reactive carbons affects the fluorescent property of the closed-ring isomers. The closed-ring isomers 2b–5b with ethyl, n-propyl, i-propyl, and i-butyl substituents show higher fluorescence quantum yields than 1b with methyl substituents. In polar solvents, the fluorescence quantum yield of 1b markedly decreases, while 2b–5b maintain the relatively high fluorescence quantum yields. Although the cycloreversion quantum yields of the derivatives with methyl, ethyl, n-propyl, and i-propyl substituents are quite low and in the order of 10−5, introduction of i-butyl substituents was found to increase the yield up to the order of 10−3. These results indicate that appropriate alkyl substitution at the reactive carbons is indispensable for properly controlling the photoswitching and fluorescent properties of the photoswitchable fluorescent diarylethenes, which are potentially applicable to super-resolution fluorescence microscopies. PMID:28869489

Structural, photoluminescence and radioluminescence properties of Eu{sup 3+} doped La{sub 2}Hf{sub 2}O{sub 7} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wahid, Kareem; Pokhrel, Madhab; Mao, Yuanbing, E-mail: yuanbing.mao@utrgv.edu

This study presents the structural, optical, and radioluminescent characterization of newly synthesized europium-doped lanthanum hafnate (La{sub 2}Hf{sub 2}O{sub 7}:xmol%Eu{sup 3+}, x=0 to 35) nanoparticles (NPs) for use as phosphors and scintillation materials. Samples prepared through a combined co-precipitation and molten salt synthetic process were found to crystalize in the pyrochlore phase, a radiation tolerant structure related to the fluorite structure. These samples exhibit red luminescence under ultraviolet and X-ray excitation. Under these excitations, the optical intensity and quantum yield of the La{sub 2}Hf{sub 2}O{sub 7}:xmol%Eu{sup 3+} NPs depend on the Eu{sup 3+} concentration and are maximized at 5%. It ismore » proposed that there is a trade-off between the quenching due to defect states/cross-relaxation and dopant concentration. An optimal dopant concentration allows the La{sub 2}Hf{sub 2}O{sub 7}:5 mol%Eu{sup 3+} NPs to show the best luminescent properties of all the samples. - Graphical abstract: Incident X-ray and UV photons interact with La{sub 2}Hf{sub 2}O{sub 7}: xmol%Eu{sup 3+}(x=1–35) nanoparticles (NPs) to yield strong red luminescence centered at 612 nm. Colored spheres inside NP diagram represent pyrochlore coordination environment of La{sub 2}Hf{sub 2}O{sub 7}:xmol%Eu{sup 3+}. Blue, red, yellow, green and black spheres represent hafnium(IV) atoms, lanthanum(III)/europium(III) atoms, oxygen atoms at 48f site, oxygen atoms at 8b site and oxygen vacancies, respectively. - Highlights: • La{sub 2}Hf{sub 2}O{sub 7}:xmol%Eu{sup 3+} (x=0–35) nanoparticles with weakly-ordered pyrochlore structures were synthesized. • Optically and X-ray excited emission spectra showed strong luminescence centered at 612 nm. • Photoluminescence quantum yield increases with doping concentration up to 5% and decreases at higher concentrations.« less

Quantum Max-flow/Min-cut

NASA Astrophysics Data System (ADS)

Cui, Shawn X.; Freedman, Michael H.; Sattath, Or; Stong, Richard; Minton, Greg

2016-06-01

The classical max-flow min-cut theorem describes transport through certain idealized classical networks. We consider the quantum analog for tensor networks. By associating an integral capacity to each edge and a tensor to each vertex in a flow network, we can also interpret it as a tensor network and, more specifically, as a linear map from the input space to the output space. The quantum max-flow is defined to be the maximal rank of this linear map over all choices of tensors. The quantum min-cut is defined to be the minimum product of the capacities of edges over all cuts of the tensor network. We show that unlike the classical case, the quantum max-flow=min-cut conjecture is not true in general. Under certain conditions, e.g., when the capacity on each edge is some power of a fixed integer, the quantum max-flow is proved to equal the quantum min-cut. However, concrete examples are also provided where the equality does not hold. We also found connections of quantum max-flow/min-cut with entropy of entanglement and the quantum satisfiability problem. We speculate that the phenomena revealed may be of interest both in spin systems in condensed matter and in quantum gravity.

Steady state quantum discord for circularly accelerated atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Jiawei, E-mail: hujiawei@nbu.edu.cn; Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn; Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081

2015-12-15

We study, in the framework of open quantum systems, the dynamics of quantum entanglement and quantum discord of two mutually independent circularly accelerated two-level atoms in interaction with a bath of fluctuating massless scalar fields in the Minkowski vacuum. We assume that the two atoms rotate synchronically with their separation perpendicular to the rotating plane. The time evolution of the quantum entanglement and quantum discord of the two-atom system is investigated. For a maximally entangled initial state, the entanglement measured by concurrence diminishes to zero within a finite time, while the quantum discord can either decrease monotonically to an asymptoticmore » value or diminish to zero at first and then followed by a revival depending on whether the initial state is antisymmetric or symmetric. When both of the two atoms are initially excited, the generation of quantum entanglement shows a delayed feature, while quantum discord is created immediately. Remarkably, the quantum discord for such a circularly accelerated two-atom system takes a nonvanishing value in the steady state, and this is distinct from what happens in both the linear acceleration case and the case of static atoms immersed in a thermal bath.« less

Entropy for quantum pure states and quantum H theorem

NASA Astrophysics Data System (ADS)

Han, Xizhi; Wu, Biao

2015-06-01

We construct a complete set of Wannier functions that are localized at both given positions and momenta. This allows us to introduce the quantum phase space, onto which a quantum pure state can be mapped unitarily. Using its probability distribution in quantum phase space, we define an entropy for a quantum pure state. We prove an inequality regarding the long-time behavior of our entropy's fluctuation. For a typical initial state, this inequality indicates that our entropy can relax dynamically to a maximized value and stay there most of time with small fluctuations. This result echoes the quantum H theorem proved by von Neumann [Zeitschrift für Physik 57, 30 (1929), 10.1007/BF01339852]. Our entropy is different from the standard von Neumann entropy, which is always zero for quantum pure states. According to our definition, a system always has bigger entropy than its subsystem even when the system is described by a pure state. As the construction of the Wannier basis can be implemented numerically, the dynamical evolution of our entropy is illustrated with an example.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mthethwa, T.P.; Moloto, M.J., E-mail: mmoloto@uj.ac.za; De Vries, A.

Graphical abstract: SEM images of CdS/PMMA showing coiling as loading of CdS nanoparticles is increased. Thermal stability is increased with increase in %loading of both CdS and CdSe nanoparticles. Research highlights: {yields} TOPO-capped CdS and HDA-capped CdSe nanoparticles were synthesized and fully characterized. {yields} The nanoparticles were mixed with the polymer, PMMA using electrospinning technique using 2, 5 and 10% weight loadings. {yields} The mixture was spun to produce fibres with optical and thermal properties showing significant change and also the increase in loading causing bending or spiraling. {yields} Both TEM images for nanoparticles and SEM for fibres shows themore » morphology and sizes of the particles. -- Abstract: Electrospinning technique was used to fabricate poly(methyl methacrylate) (PMMA) fibres incorporating CdS and CdSe quantum dots (nanoparticles). Different nanoparticle loadings (2, 5 and 10 wt% with respect to PMMA) were used and the effect of the quantum dots on the properties of the fibres was studied. The optical properties of the hybrid composite fibres were investigated by photoluminescence and UV-vis spectrophotometry. Scanning electron microscopy (SEM), X-ray diffraction and FTIR spectrophotometry were also used to investigate the morphology and structure of the fibres. The optical studies showed that the size-tunable optical properties can be achieved in the polymer fibres by addition of quantum dots. SEM images showed that the morphologies of the fibres were dependent on the added amounts of quantum dots. A spiral type of morphology was observed with an increase in the concentration of CdS and CdSe nanoparticles. Less beaded structures and bigger diameter fibres were obtained at higher quantum dot concentrations. X-ray diffractometry detected the amorphous peaks of the polymer and even after the quantum dots were added and the FTIR analysis shows that there was no considerable interaction between the quantum dots and the polymer fibres at low concentration of quantum dots however at higher concentrations some interactions were observed which shows that QDs were present on the surfaces of the fibres.« less

Thermoelectric properties of an interacting quantum dot based heat engine

NASA Astrophysics Data System (ADS)

Erdman, Paolo Andrea; Mazza, Francesco; Bosisio, Riccardo; Benenti, Giuliano; Fazio, Rosario; Taddei, Fabio

2017-06-01

We study the thermoelectric properties and heat-to-work conversion performance of an interacting, multilevel quantum dot (QD) weakly coupled to electronic reservoirs. We focus on the sequential tunneling regime. The dynamics of the charge in the QD is studied by means of master equations for the probabilities of occupation. From here we compute the charge and heat currents in the linear response regime. Assuming a generic multiterminal setup, and for low temperatures (quantum limit), we obtain analytical expressions for the transport coefficients which account for the interplay between interactions (charging energy) and level quantization. In the case of systems with two and three terminals we derive formulas for the power factor Q and the figure of merit Z T for a QD-based heat engine, identifying optimal working conditions which maximize output power and efficiency of heat-to-work conversion. Beyond the linear response we concentrate on the two-terminal setup. We first study the thermoelectric nonlinear coefficients assessing the consequences of large temperature and voltage biases, focusing on the breakdown of the Onsager reciprocal relation between thermopower and Peltier coefficient. We then investigate the conditions which optimize the performance of a heat engine, finding that in the quantum limit output power and efficiency at maximum power can almost be simultaneously maximized by choosing appropriate values of electrochemical potential and bias voltage. At last we study how energy level degeneracy can increase the output power.

A research on service quality decision-making of Chinese communications industry based on quantum game

NASA Astrophysics Data System (ADS)

Zhang, Cuihua; Xing, Peng

2015-08-01

In recent years, Chinese service industry is developing rapidly. Compared with developed countries, service quality should be the bottleneck for Chinese service industry. On the background of three major telecommunications service providers in China, the functions of customer perceived utilities are established. With the goal of consumer's perceived utility maximization, the classic Nash equilibrium solution and quantum equilibrium solution are obtained. Then a numerical example is studied and the changing trend of service quality and customer perceived utility is further analyzed by the influence of the entanglement operator. Finally, it is proved that quantum game solution is better than Nash equilibrium solution.

General method for extracting the quantum efficiency of dispersive qubit readout in circuit QED

NASA Astrophysics Data System (ADS)

Bultink, C. C.; Tarasinski, B.; Haandbæk, N.; Poletto, S.; Haider, N.; Michalak, D. J.; Bruno, A.; DiCarlo, L.

2018-02-01

We present and demonstrate a general three-step method for extracting the quantum efficiency of dispersive qubit readout in circuit QED. We use active depletion of post-measurement photons and optimal integration weight functions on two quadratures to maximize the signal-to-noise ratio of the non-steady-state homodyne measurement. We derive analytically and demonstrate experimentally that the method robustly extracts the quantum efficiency for arbitrary readout conditions in the linear regime. We use the proven method to optimally bias a Josephson traveling-wave parametric amplifier and to quantify different noise contributions in the readout amplification chain.

A synchronous game for binary constraint systems

NASA Astrophysics Data System (ADS)

Kim, Se-Jin; Paulsen, Vern; Schafhauser, Christopher

2018-03-01

Recently, Slofstra proved that the set of quantum correlations is not closed. We prove that the set of synchronous quantum correlations is not closed, which implies his result, by giving an example of a synchronous game that has a perfect quantum approximate strategy but no perfect quantum strategy. We also exhibit a graph for which the quantum independence number and the quantum approximate independence number are different. We prove new characterisations of synchronous quantum approximate correlations and synchronous quantum spatial correlations. We solve the synchronous approximation problem of Dykema and the second author, which yields a new equivalence of Connes' embedding problem in terms of synchronous correlations.

Raising yield potential in wheat: increasing photosynthesis capacity and efficiency

USDA-ARS?s Scientific Manuscript database

Increasing wheat yields to help to ensure food security is a major challenge. Meeting this challenge requires a quantum improvement in the yield potential of wheat. Past increases in yield potential have largely resulted from improvements in harvest index not through increased biomass. Further large...

Correlation complementarity yields bell monogamy relations.

PubMed

Kurzyński, P; Paterek, T; Ramanathan, R; Laskowski, W; Kaszlikowski, D

2011-05-06

We present a method to derive Bell monogamy relations by connecting the complementarity principle with quantum nonlocality. The resulting monogamy relations are stronger than those obtained from the no-signaling principle alone. In many cases, they yield tight quantum bounds on the amount of violation of single and multiple qubit correlation Bell inequalities. In contrast with the two-qubit case, a rich structure of possible violation patterns is shown to exist in the multipartite scenario.

The effect of axial ligands on the quantum yield of singlet oxygen of new silicon phthalocyanine

NASA Astrophysics Data System (ADS)

Lv, Huafei; Zhang, Xuemei; Yu, Xinxin; Pan, Sujuan; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2016-10-01

The singlet oxygen (1O2) production abilitity is an important factor to assess their potential as effective of photosensitizers. In this paper, the 1O2 production rate, production rate constant and quantum yield of silicon(IV) phthalocyanine axially bearing 1-3 generation dendritic substituents were evaluated by a high performance liquid chromatographic method. The results show that the 1O2 production rate and production rate constant of these compounds increase gradually with dendritic generations increase. And the 1O2 quantum yield of silicon(IV) phthalocyanine with first generation dendritic ligand was the highest. This may be due to the isolation effect of the dendritic ligands on the phthalocyanine core. The parameters of the observed 1O2 production properties will provide valuable data for these dendrimer phthalocyanines as promising photosensitizer in PDT application.

Photochemical studies of a fluorescent chlorophyll catabolite--source of bright blue fluorescence in plant tissue and efficient sensitizer of singlet oxygen.

PubMed

Jockusch, Steffen; Turro, Nicholas J; Banala, Srinivas; Kräutler, Bernhard

2014-02-01

Fluorescent chlorophyll catabolites (FCCs) are fleeting intermediates of chlorophyll breakdown, which is seen as an enzyme controlled detoxification process of the chlorophylls in plants. However, some plants accumulate large amounts of persistent FCCs, such as in senescent leaves and in peels of yellow bananas. The photophysical properties of such a persistent FCC (Me-sFCC) were investigated in detail. FCCs absorb in the near UV spectral region and show blue fluorescence (max at 437 nm). The Me-sFCC fluorescence had a quantum yield of 0.21 (lifetime 1.6 ns). Photoexcited Me-sFCC intersystem crosses into the triplet state (quantum yield 0.6) and generates efficiently singlet oxygen (quantum yield 0.59). The efficient generation of singlet oxygen makes fluorescent chlorophyll catabolites phototoxic, but might also be useful as a (stress) signal and for defense of the plant tissue against infection by pathogens.

Short-Term Flooding Effects on Gas Exchange and Quantum Yield of Rabbiteye Blueberry (Vaccinium ashei Reade) 1

PubMed Central

Davies, Frederick S.; Flore, James A.

1986-01-01

Roots of 1.5-year-old `Woodard' rabbiteye blueberry plants (Vaccinium ashei Reade) were flooded in containers or maintained at container capacity over a 5-day period. Carbon assimilation, and stomatal and residual conductances were monitored on one fully expanded shoot/plant using an open flow gas analysis system. Quantum yield was calculated from light response curves. Carbon assimilation and quantum yield of flooded plants decreased to 64 and 41% of control values, respectively, after 1 day of flooding and continued decreasing to 38 and 27% after 4 days. Stomatal and residual conductances to CO2 also decreased after 1 day of flooding compared with those of unflooded plants with residual conductance severely limiting carbon assimilation after 4 days of flooding. Stomatal opening occurred in 75 to 90 minutes and rate of opening was unaffected by flooding. PMID:16664791

Qutrit Magic State Distillation Tight in Some Directions.

PubMed

Dawkins, Hillary; Howard, Mark

2015-07-17

Magic state distillation is a crucial component in the leading approaches to implementing universal fault-tolerant quantum computation, with existing protocols for both qubit and higher dimensional systems. Early work focused on determining the region of distillable states for qubit protocols; yet comparatively little is known about which states can be distilled and with what distillable region for d>2. Here we focus on d=3 and present new four-qutrit distillation schemes that improve upon the known distillable region, and achieve distillation tight to the boundary of undistillable states for some classes of state. As a consequence of recent results, this implies that there is a family of quantum states that enable universality if and only if they exhibit contextuality with respect to stabilizer measurements. We also identify a new routine whose fixed point is a magic state with maximal sum negativity; i.e., it is maximally nonstablizer in a specific sense.

InGaP Heterojunction Barrier Solar Cells

NASA Technical Reports Server (NTRS)

Welser, Roger E. (Inventor)

2014-01-01

A new solar cell structure called a heterojunction barrier solar cell is described. As with previously reported quantum-well and quantum-dot solar cell structures, a layer of narrow band-gap material, such as GaAs or indium-rich InGaP, is inserted into the depletion region of a wide band-gap PN junction. Rather than being thin, however, the layer of narrow band-gap material is about 400-430 nm wide and forms a single, ultrawide well in the depletion region. Thin (e.g., 20-50 nm), wide band-gap InGaP barrier layers in the depletion region reduce the diode dark current. Engineering the electric field and barrier profile of the absorber layer, barrier layer, and p-type layer of the PN junction maximizes photogenerated carrier escape. This new twist on nanostructured solar cell design allows the separate optimization of current and voltage to maximize conversion efficiency.

New Maximally Entangled States for Pattern-Association Through Evolutionary Processes in a Two-Qubit System

NASA Astrophysics Data System (ADS)

Singh, Manu Pratap; Rajput, Balwant S.

2017-04-01

New set of maximally entangled states (Singh-Rajput MES), constituting orthonormal eigen bases, has been revisited and its superiority and suitability in pattern-association (Quantum Associative Memory, QuAM) have been demonstrated. Using these MES as memory states in the evolutionary process of pattern storage in a two-qubit system, it has been shown that the first two states of Singh-Rajput MES are useful for storing the pattern |11> and the last two of these MES are useful in storing the pattern |10> Recall operations of quantum associate memory (QuAM) have been conducted through evolutionary process in terms of unitary operators by separately choosing Singh-Rajput MES and Bell's MES as memory states and it has been shown that Singh-Rajput MES as valid memory states for recalling the patterns in a two-qubit system are much more suitable than Bell's MES.

Nonlocal hyperconcentration on entangled photons using photonic module system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Cong; Wang, Tie-Jun; Mi, Si-Chen

Entanglement distribution will inevitably be affected by the channel and environment noise. Thus distillation of maximal entanglement nonlocally becomes a crucial goal in quantum information. Here we illustrate that maximal hyperentanglement on nonlocal photons could be distilled using the photonic module and cavity quantum electrodynamics, where the photons are simultaneously entangled in polarization and spatial-mode degrees of freedom. The construction of the photonic module in a photonic band-gap structure is presented, and the operation of the module is utilized to implement the photonic nondestructive parity checks on the two degrees of freedom. We first propose a hyperconcentration protocol using twomore » identical partially hyperentangled initial states with unknown coefficients to distill a maximally hyperentangled state probabilistically, and further propose a protocol by the assistance of an ancillary single photon prepared according to the known coefficients of the initial state. In the two protocols, the total success probability can be improved greatly by introducing the iteration mechanism, and only one of the remote parties is required to perform the parity checks in each round of iteration. Estimates on the system requirements and recent experimental results indicate that our proposal is realizable with existing or near-further technologies.« less

Physical-layer security analysis of PSK quantum-noise randomized cipher in optically amplified links

NASA Astrophysics Data System (ADS)

Jiao, Haisong; Pu, Tao; Xiang, Peng; Zheng, Jilin; Fang, Tao; Zhu, Huatao

2017-08-01

The quantitative security of quantum-noise randomized cipher (QNRC) in optically amplified links is analyzed from the perspective of physical-layer advantage. Establishing the wire-tap channel models for both key and data, we derive the general expressions of secrecy capacities for the key against ciphertext-only attack and known-plaintext attack, and that for the data, which serve as the basic performance metrics. Further, the maximal achievable secrecy rate of the system is proposed, under which secrecy of both the key and data is guaranteed. Based on the same framework, the secrecy capacities of various cases can be assessed and compared. The results indicate perfect secrecy is potentially achievable for data transmission, and an elementary principle of setting proper number of photons and bases is given to ensure the maximal data secrecy capacity. But the key security is asymptotically perfect, which tends to be the main constraint of systemic maximal secrecy rate. Moreover, by adopting cascaded optical amplification, QNRC can realize long-haul transmission with secure rate up to Gb/s, which is orders of magnitude higher than the perfect secrecy rates of other encryption systems.

Fundamental Quantum 1/F Noise in Ultrasmall Semiconductor Devices and Their Optimal Design Principles

DTIC Science & Technology

1988-05-31

Hooge parameter. 2. 1 / f Noise of the Recombination Current Generated in the Depletion Region The quantum i/ f ...theory. There are two forms of quantum 11f noise . In the first place C~ and Cn4 p n to quantum 1 / f noise theory. This would yield Hooge parameters S...Fundamental Quantum 1 / f Noise in Ultrasmall S~ iodcrD’vesadOtm.Dsgn P in. 12. PERSONAL AUTHOR(S) Handel, Peter H. (Princioal investiaat r) 13a. TYPE

Proceedings of the Quantum Computation for Physical Modeling Workshop 2004. Held in North Falmouth, MA on 12-15 September 2004

DTIC Science & Technology

2005-10-01

late the difficulty of some basic 1-bit and n-bit quantum and classical operations in an simple unconstrained scenario. KEY WORDS: Time evolution... quantum circuit and design are presented for an optimized entangling probe attacking the BB84 Protocol of quantum key distribution (QKD) and yielding...unambiguous, at least some of the time. It follows that the BB84 (Bennett-Brassard 1984) proto- col of quantum key distribution has a vulnerability similar to

Interaction of Water-Soluble CdTe Quantum Dots with Bovine Serum Albumin

PubMed Central

2011-01-01

Semiconductor nanoparticles (quantum dots) are promising fluorescent markers, but it is very little known about interaction of quantum dots with biological molecules. In this study, interaction of CdTe quantum dots coated with thioglycolic acid (TGA) with bovine serum albumin was investigated. Steady state spectroscopy, atomic force microscopy, electron microscopy and dynamic light scattering methods were used. It was explored how bovine serum albumin affects stability and spectral properties of quantum dots in aqueous media. CdTe–TGA quantum dots in aqueous solution appeared to be not stable and precipitated. Interaction with bovine serum albumin significantly enhanced stability and photoluminescence quantum yield of quantum dots and prevented quantum dots from aggregating. PMID:27502633

Can time-dependent density functional theory predict intersystem crossing in organic chromophores? A case study on benzo(bis)-X-diazole based donor-acceptor-donor type molecules.

PubMed

Tam, Teck Lip Dexter; Lin, Ting Ting; Chua, Ming Hui

2017-06-21

Here we utilized new diagnostic tools in time-dependent density functional theory to explain the trend of intersystem crossing in benzo(bis)-X-diazole based donor-acceptor-donor type molecules. These molecules display a wide range of fluorescence quantum yields and triplet yields, making them excellent candidates for testing the validity of these diagnostic tools. We believe that these tools are cost-effective and can be applied to structurally similar organic chromophores to predict/explain the trends of intersystem crossing, and thus fluorescence quantum yields and triplet yields without the use of complex and expensive multireference configuration interaction or multireference pertubation theory methods.

Entanglement-seeded, dual, optical parametric amplification: Applications to quantum imaging and metrology

NASA Astrophysics Data System (ADS)

Glasser, Ryan T.; Cable, Hugo; Dowling, Jonathan P.; de Martini, Francesco; Sciarrino, Fabio; Vitelli, Chiara

2008-07-01

The study of optical parametric amplifiers (OPAs) has been successful in describing and creating nonclassical light for use in fields such as quantum metrology and quantum lithography [Agarwal , J. Opt. Soc. Am. B 24, 2 (2007)]. In this paper we present the theory of an OPA scheme utilizing an entangled state input. The scheme involves two identical OPAs seeded with the maximally path-entangled ∣N00N⟩ state (∣2,0⟩+∣0,2⟩)/2 . The stimulated amplification results in output state probability amplitudes that have a dependence on the number of photons in each mode, which differs greatly from two-mode squeezed vacuum. A large family of entangled output states are found. Specific output states allow for the heralded creation of N=4 N00N states, which may be used for quantum lithography, to write sub-Rayleigh fringe patterns, and for quantum interferometry, to achieve Heisenberg-limited phase measurement sensitivity.

Enhancing quantum effects via periodic modulations in optomechanical systems

NASA Astrophysics Data System (ADS)

Farace, Alessandro; Giovannetti, Vittorio

2012-07-01

Parametrically modulated optomechanical systems have been recently proposed as a simple and efficient setting for the quantum control of a micromechanical oscillator: relevant possibilities include the generation of squeezing in the oscillator position (or momentum) and the enhancement of entanglement between mechanical and radiation modes. In this paper we further investigate this modulation regime, considering an optomechanical system with one or more parameters being modulated over time. We first apply a sinusoidal modulation of the mechanical frequency and characterize the optimal regime in which the visibility of purely quantum effects is maximal. We then introduce a second modulation on the input laser intensity and analyze the interplay between the two. We find that an interference pattern shows up, so that different choices of the relative phase between the two modulations can either enhance or cancel the desired quantum effects, opening new possibilities for optimal quantum control strategies.

The quantum Zeno effect in double well tunnelling

NASA Astrophysics Data System (ADS)

Lerner, L.

2018-05-01

Measurement lies at the heart of quantum theory, and introductory textbooks in quantum mechanics cover the measurement problem in topics such as the Schrödinger’s cat thought experiment, the EPR problem, and the quantum Zeno effect (QZE). In this article we present a new treatment of the QZE suitable for undergraduate students, for the case of a particle tunnelling between two wells while being observed in one of the wells. The analysis shows that as the observation rate increases, the tunnelling rate tends towards zero, in accordance with Zeno’s maxim ‘a watched pot never boils’. The method relies on decoherence theory, which replaces aspects of quantum collapse by the Schrödinger evolution of an open system, and its recently simplified treatment for undergraduates. Our presentation uses concepts familiar to undergraduate students, so that calculations involving many-body theory and the formal properties of the density matrix are avoided.

The elusive Heisenberg limit in quantum-enhanced metrology

PubMed Central

Demkowicz-Dobrzański, Rafał; Kołodyński, Jan; Guţă, Mădălin

2012-01-01

Quantum precision enhancement is of fundamental importance for the development of advanced metrological optical experiments, such as gravitational wave detection and frequency calibration with atomic clocks. Precision in these experiments is strongly limited by the 1/√N shot noise factor with N being the number of probes (photons, atoms) employed in the experiment. Quantum theory provides tools to overcome the bound by using entangled probes. In an idealized scenario this gives rise to the Heisenberg scaling of precision 1/N. Here we show that when decoherence is taken into account, the maximal possible quantum enhancement in the asymptotic limit of infinite N amounts generically to a constant factor rather than quadratic improvement. We provide efficient and intuitive tools for deriving the bounds based on the geometry of quantum channels and semi-definite programming. We apply these tools to derive bounds for models of decoherence relevant for metrological applications including: depolarization, dephasing, spontaneous emission and photon loss. PMID:22990859

Brachistochrone of entanglement for spin chains

NASA Astrophysics Data System (ADS)

Carlini, Alberto; Koike, Tatsuhiko

2017-03-01

We analytically investigate the role of entanglement in time-optimal state evolution as an application of the quantum brachistochrone, a general method for obtaining the optimal time-dependent Hamiltonian for reaching a target quantum state. As a model, we treat two qubits indirectly coupled through an intermediate qubit that is directly controllable, which represents a typical situation in quantum information processing. We find the time-optimal unitary evolution law and quantify residual entanglement by the two-tangle between the indirectly coupled qubits, for all possible sets of initial pure quantum states of a tripartite system. The integrals of the motion of the brachistochrone are determined by fixing the minimal time at which the residual entanglement is maximized. Entanglement plays a role for W and Greenberger-Horne-Zeilinger (GHz) initial quantum states, and for the bi-separable initial state in which the indirectly coupled qubits have a nonzero value of the 2-tangle.

Quantum Landauer erasure with a molecular nanomagnet

NASA Astrophysics Data System (ADS)

Gaudenzi, R.; Burzurí, E.; Maegawa, S.; van der Zant, H. S. J.; Luis, F.

2018-06-01

The erasure of a bit of information is an irreversible operation whose minimal entropy production of kB ln 2 is set by the Landauer limit1. This limit has been verified in a variety of classical systems, including particles in traps2,3 and nanomagnets4. Here, we extend it to the quantum realm by using a crystal of molecular nanomagnets as a quantum spin memory and showing that its erasure is still governed by the Landauer principle. In contrast to classical systems, maximal energy efficiency is achieved while preserving fast operation owing to its high-speed spin dynamics. The performance of our spin register in terms of energy-time cost is orders of magnitude better than existing memory devices to date. The result shows that thermodynamics sets a limit on the energy cost of certain quantum operations and illustrates a way to enhance classical computations by using a quantum system.

Entropy production of doubly stochastic quantum channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Müller-Hermes, Alexander, E-mail: muellerh@posteo.net; Department of Mathematical Sciences, University of Copenhagen, 2100 Copenhagen; Stilck França, Daniel, E-mail: dsfranca@mytum.de

2016-02-15

We study the entropy increase of quantum systems evolving under primitive, doubly stochastic Markovian noise and thus converging to the maximally mixed state. This entropy increase can be quantified by a logarithmic-Sobolev constant of the Liouvillian generating the noise. We prove a universal lower bound on this constant that stays invariant under taking tensor-powers. Our methods involve a new comparison method to relate logarithmic-Sobolev constants of different Liouvillians and a technique to compute logarithmic-Sobolev inequalities of Liouvillians with eigenvectors forming a projective representation of a finite abelian group. Our bounds improve upon similar results established before and as an applicationmore » we prove an upper bound on continuous-time quantum capacities. In the last part of this work we study entropy production estimates of discrete-time doubly stochastic quantum channels by extending the framework of discrete-time logarithmic-Sobolev inequalities to the quantum case.« less

Continuous-variable quantum probes for structured environments

NASA Astrophysics Data System (ADS)

Bina, Matteo; Grasselli, Federico; Paris, Matteo G. A.

2018-01-01

We address parameter estimation for structured environments and suggest an effective estimation scheme based on continuous-variables quantum probes. In particular, we investigate the use of a single bosonic mode as a probe for Ohmic reservoirs, and obtain the ultimate quantum limits to the precise estimation of their cutoff frequency. We assume the probe prepared in a Gaussian state and determine the optimal working regime, i.e., the conditions for the maximization of the quantum Fisher information in terms of the initial preparation, the reservoir temperature, and the interaction time. Upon investigating the Fisher information of feasible measurements, we arrive at a remarkable simple result: homodyne detection of canonical variables allows one to achieve the ultimate quantum limit to precision under suitable, mild, conditions. Finally, upon exploiting a perturbative approach, we find the invariant sweet spots of the (tunable) characteristic frequency of the probe, able to drive the probe towards the optimal working regime.

Quantum coherence effects in natural light-induced processes: cis-trans photoisomerization of model retinal under incoherent excitation.

PubMed

Tscherbul, Timur V; Brumer, Paul

2015-12-14

We present a theoretical study of quantum coherence effects in the primary cis-trans photoisomerization of retinal in rhodopsin induced by incoherent solar light. Using the partial secular Bloch-Redfield quantum master equation approach based on a two-state two-mode linear vibronic coupling model of the retinal chromophore [S. Hahn and G. Stock, J. Phys. Chem. B, 2000, 104, 1146-1149], we show that a sudden turn-on of incoherent pumping can generate substantial Fano coherences among the excited states of retinal. These coherences are the most pronounced in the regime where the matrix elements of the transition dipole moment between the ground and excited eigenstates are parallel to one another. We show that even when the transition dipole moments are perpendicular (implying the absence of light-induced Fano coherence) a small amount of excited-state coherence is still generated due to the coupling to intramolecular vibrational modes and the protein environment, causing depopulation of the excited eigenstates. The overall effect of the coherences on the steady-state population and on the photoproduct quantum yield is shown to be small; however we observe a significant transient effect on the formation of the trans photoproduct, enhancing the photoreaction quantum yield by ∼11% at 200 fs. These calculations suggest that coupling to intramolecular vibrational modes and the protein environment play an important role in photoreaction dynamics, suppressing oscillations in the quantum yield associated with Fano interference.

Gaussian quantum steering and its asymmetry in curved spacetime

NASA Astrophysics Data System (ADS)

Wang, Jieci; Cao, Haixin; Jing, Jiliang; Fan, Heng

2016-06-01

We study Gaussian quantum steering and its asymmetry in the background of a Schwarzschild black hole. We present a Gaussian channel description of quantum state evolution under the influence of Hawking radiation. We find that thermal noise introduced by the Hawking effect will destroy the steerability between an inertial observer Alice and an accelerated observer Bob who hovers outside the event horizon, while it generates steerability between Bob and a hypothetical observer anti-Bob inside the event horizon. Unlike entanglement behaviors in curved spacetime, here the steering from Alice to Bob suffers from a "sudden death" and the steering from anti-Bob to Bob experiences a "sudden birth" with increasing Hawking temperature. We also find that the Gaussian steering is always asymmetric and the maximum steering asymmetry cannot exceed ln 2 , which means the state never evolves to an extremal asymmetry state. Furthermore, we obtain the parameter settings that maximize steering asymmetry and find that (i) s =arccosh cosh/2r 1 -sinh2r is the critical point of steering asymmetry and (ii) the attainment of maximal steering asymmetry indicates the transition between one-way steerability and both-way steerability for the two-mode Gaussian state under the influence of Hawking radiation.

Maximizing Lipid Yield in Neochloris oleoabundans Algae Extraction by Stressing and Using Multiple Extraction Stages with N-Ethylbutylamine as Switchable Solvent

PubMed Central

2017-01-01

The extraction yield of lipids from nonbroken Neochloris oleoabundans was maximized by using multiple extraction stages and using stressed algae. Experimental parameters that affect the extraction were investigated. The study showed that with wet algae (at least) 18 h extraction time was required for maximum yield at room temperature and a solvent/feed ratio of 1:1 (w/w). For fresh water (FW), nonstressed, nonbroken Neochloris oleoabundans, 13.1 wt % of lipid extraction yield (based on dry algae mass) was achieved, which could be improved to 61.3 wt % for FW stressed algae after four extractions, illustrating that a combination of stressing the algae and applying the solvent N-ethylbutylamine in multiple stages of extraction results in almost 5 times higher yield and is very promising for further development of energy-efficient lipid extraction technology targeting nonbroken wet microalgae. PMID:28781427

Lunisolar tidal force and its relationship to chlorophyll fluorescence in Arabidopsis thaliana.

PubMed

Fisahn, Joachim; Klingelé, Emile; Barlow, Peter

2015-01-01

The yield of chlorophyll fluorescence Ft was measured in leaves of Arabidopsis thaliana over periods of several days under conditions of continuous illumination (LL) without the application of saturating light pulses. After linearization of the time series of the chlorophyll fluorescence yield (ΔFt), oscillations became apparent with periodicities in the circatidal range. Alignments of these linearized time series ΔFt with the lunisolar tidal acceleration revealed high degrees of synchrony and phase congruence. Similar congruence with the lunisolar tide was obtained with the linearized quantum yield of PSII (ΔФII), recorded after application of saturating light pulses. These findings strongly suggest that there is an exogenous timekeeper which is a stimulus for the oscillations detected in both the linearized yield of chlorophyll fluorescence (ΔFt) and the linearized quantum yield of PSII (ΔФII).

Lunisolar tidal force and its relationship to chlorophyll fluorescence in Arabidopsis thaliana

PubMed Central

Fisahn, Joachim; Klingelé, Emile; Barlow, Peter

2015-01-01

The yield of chlorophyll fluorescence Ft was measured in leaves of Arabidopsis thaliana over periods of several days under conditions of continuous illumination (LL) without the application of saturating light pulses. After linearization of the time series of the chlorophyll fluorescence yield (ΔFt), oscillations became apparent with periodicities in the circatidal range. Alignments of these linearized time series ΔFt with the lunisolar tidal acceleration revealed high degrees of synchrony and phase congruence. Similar congruence with the lunisolar tide was obtained with the linearized quantum yield of PSII (ΔФII), recorded after application of saturating light pulses. These findings strongly suggest that there is an exogenous timekeeper which is a stimulus for the oscillations detected in both the linearized yield of chlorophyll fluorescence (ΔFt) and the linearized quantum yield of PSII (ΔФII). PMID:26376108

Matching relations for optimal entanglement concentration and purification

PubMed Central

Kong, Fan-Zhen; Xia, Hui-Zhi; Yang, Ming; Yang, Qing; Cao, Zhuo-Liang

2016-01-01

The bilateral controlled NOT (CNOT) operation plays a key role in standard entanglement purification process, but the CNOT operation may not be the optimal joint operation in the sense that the output entanglement is maximized. In this paper, the CNOT operations in both the Schmidt-projection based entanglement concentration and the entanglement purification schemes are replaced with a general joint unitary operation, and the optimal matching relations between the entangling power of the joint unitary operation and the non-maximal entangled channel are found for optimizing the entanglement in- crement or the output entanglement. The result is somewhat counter-intuitive for entanglement concentration. The output entanglement is maximized when the entangling power of the joint unitary operation and the quantum channel satisfy certain relation. There exist a variety of joint operations with non-maximal entangling power that can induce a maximal output entanglement, which will greatly broaden the set of the potential joint operations in entanglement concentration. In addition, the entanglement increment in purification process is maximized only by the joint unitary operations (including CNOT) with maximal entangling power. PMID:27189800

New quantum codes constructed from quaternary BCH codes

NASA Astrophysics Data System (ADS)

Xu, Gen; Li, Ruihu; Guo, Luobin; Ma, Yuena

2016-10-01

In this paper, we firstly study construction of new quantum error-correcting codes (QECCs) from three classes of quaternary imprimitive BCH codes. As a result, the improved maximal designed distance of these narrow-sense imprimitive Hermitian dual-containing quaternary BCH codes are determined to be much larger than the result given according to Aly et al. (IEEE Trans Inf Theory 53:1183-1188, 2007) for each different code length. Thus, families of new QECCs are newly obtained, and the constructed QECCs have larger distance than those in the previous literature. Secondly, we apply a combinatorial construction to the imprimitive BCH codes with their corresponding primitive counterpart and construct many new linear quantum codes with good parameters, some of which have parameters exceeding the finite Gilbert-Varshamov bound for linear quantum codes.

High quantum yield of the Egyptian blue family of infrared phosphors (MCuSi4O10, M = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Berdahl, Paul; Boocock, Simon K.; Chan, George C.-Y.; Chen, Sharon S.; Levinson, Ronnen M.; Zalich, Michael A.

2018-05-01

The alkaline earth copper tetra-silicates, blue pigments, are interesting infrared phosphors. The Ca, Sr, and Ba variants fluoresce in the near-infrared (NIR) at 909, 914, and 948 nm, respectively, with spectral widths on the order of 120 nm. The highest quantum yield ϕ reported thus far is ca. 10%. We use temperature measurements in sunlight to determine this parameter. The yield depends on the pigment loading (mass per unit area) ω with values approaching 100% as ω → 0 for the Ca and Sr variants. Although maximum quantum yield occurs near ω = 0, maximum fluorescence occurs near ω = 70 g m-2, at which ϕ = 0.7. The better samples show fluorescence decay times in the range of 130 to 160 μs. The absorbing impurity CuO is often present. Good phosphor performance requires long fluorescence decay times and very low levels of parasitic absorption. The strong fluorescence enhances prospects for energy applications such as cooling of sunlit surfaces (to reduce air conditioning requirements) and luminescent solar concentrators.

Temporal variability in chlorophyll fluorescence of back-reef corals in Ofu, American Samoa

USGS Publications Warehouse

Piniak, G.A.; Brown, E.K.

2009-01-01

Change in the yield of chlorophyll a fluorescence is a common indicator of thermal stress in corals. The present study reports temporal variability in quantum yield measurements for 10 coral species in Ofu, American Samoa - a place known to experience elevated and variable seawater temperatures. In winter, the zooxanthellae generally had higher dark-adapted maximum quantum yield (F v/Fm), higher light- adapted effective quantum yield (??F/F'm), and lower relative electron transport rates (rETR) than in the summer. Temporal changes appeared unrelated to the expected bleaching sensitivity of corals. All species surveyed, with the exception of Montipora grisea, demonstrated significant temporal changes in the three fluorescence parameters. Fluorescence responses were influenced by the microhabitat - temporal differences in fluorescence parameters were usually observed in the habitat with a more variable temperature regime (pool 300), while differences in Fv/Fm between species were observed only in the more environmentally stable habitat (pool 400). Such species-specific responses and microhabitat variability should be considered when attempting to determine whether observed in situ changes are normal seasonal changes or early signs of bleaching. ?? 2009 Marine Biological Laboratory.

Photodynamic therapy potential of thiol-stabilized CdTe quantum dot-group 3A phthalocyanine conjugates (QD-Pc).

PubMed

Tekdaş, Duygu Aydın; Durmuş, Mahmut; Yanık, Hülya; Ahsen, Vefa

2012-07-01

Thiol stabilized CdTe quantum dot (QD) nanoparticles were synthesized in aqueous phase and were used as energy donors to tetra-triethyleneoxythia substituted aluminum, gallium and indium phthalocyanines through fluorescence resonance energy transfer (FRET). Energy transfer occurred from the QDs to phthalocyanines upon photoexcitation of the QDs. An enhancement in efficiency of energy transfer with the nature of the carboxylic thiol stabilizer on the QDs was observed. As a result of the nanoparticle and the phthalocyanine mixing, the photoluminescence efficiency of the phthalocyanine moieties in the mixtures does not strictly follow the quantum yields of the bare phthalocyanines. The photochemistry study of phthalocyanines in the presence of the QDs revealed high singlet oxygen quantum yield, hence the possibility of using QDs in combination with phthalocyanines as photosensitizers in photodynamic therapy of cancer. The fluorescence of the CdTe quantum dots-phthalocyanine conjugates (QDs-Pc) were effectively quenched by addition of 1,4-benzoquinone. Copyright © 2012 Elsevier B.V. All rights reserved.

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

PubMed Central

Schröder, Tim; Trusheim, Matthew E.; Walsh, Michael; Li, Luozhou; Zheng, Jiabao; Schukraft, Marco; Sipahigil, Alp; Evans, Ruffin E.; Sukachev, Denis D.; Nguyen, Christian T.; Pacheco, Jose L.; Camacho, Ryan M.; Bielejec, Edward S.; Lukin, Mikhail D.; Englund, Dirk

2017-01-01

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ∼32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ∼2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ∼51 GHz and close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ∼1.4 times the natural linewidth. This method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors. PMID:28548097

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

DOE PAGES

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael; ...

2017-05-26

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Improved Charge-Transfer Fluorescent Dyes

NASA Technical Reports Server (NTRS)

Meador, Michael

2005-01-01

Improved charge-transfer fluorescent dyes have been developed for use as molecular probes. These dyes are based on benzofuran nuclei with attached phenyl groups substituted with, variously, electron donors, electron acceptors, or combinations of donors and acceptors. Optionally, these dyes could be incorporated as parts of polymer backbones or as pendant groups or attached to certain surfaces via self-assembly-based methods. These dyes exhibit high fluorescence quantum yields -- ranging from 0.2 to 0.98, depending upon solvents and chemical structures. The wavelengths, quantum yields, intensities, and lifetimes of the fluorescence emitted by these dyes vary with (and, hence, can be used as indicators of) the polarities of solvents in which they are dissolved: In solvents of increasing polarity, fluorescence spectra shift to longer wavelengths, fluorescence quantum yields decrease, and fluorescence lifetimes increase. The wavelengths, quantum yields, intensities, and lifetimes are also expected to be sensitive to viscosities and/or glass-transition temperatures. Some chemical species -- especially amines, amino acids, and metal ions -- quench the fluorescence of these dyes, with consequent reductions in intensities, quantum yields, and lifetimes. As a result, the dyes can be used to detect these species. Another useful characteristic of these dyes is a capability for both two-photon and one-photon absorption. Typically, these dyes absorb single photons in the ultraviolet region of the spectrum (wavelengths < 400 nm) and emit photons in the long-wavelength ultraviolet, visible, and, when dissolved in some solvents, near-infrared regions. In addition, these dyes can be excited by two-photon absorption at near-infrared wavelengths (600 to 800 nm) to produce fluorescence spectra identical to those obtained in response to excitation by single photons at half the corresponding wavelengths (300 to 400 nm). While many prior fluorescent dyes exhibit high quantum yields, solvent-polarity- dependent fluorescence behavior, susceptibility to quenching by certain chemical species, and/or two-photon fluorescence, none of them has the combination of all of these attributes. Because the present dyes do have all of these attributes, they have potential utility as molecular probes in a variety of applications. Examples include (1) monitoring curing and deterioration of polymers; (2) monitoring protein expression; (3) high-throughput screening of drugs; (4) monitoring such chemical species as glucose, amines, amino acids, and metal ions; and (5) photodynamic therapy of cancers and other diseases.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lifeng, E-mail: walfe@nuaa.edu.cn; Hu, Haiyan

The thermal vibration of a rectangular single-layered graphene sheet is investigated by using a rectangular nonlocal elastic plate model with quantum effects taken into account when the law of energy equipartition is unreliable. The relation between the temperature and the Root of Mean Squared (RMS) amplitude of vibration at any point of the rectangular single-layered graphene sheet in simply supported case is derived first from the rectangular nonlocal elastic plate model with the strain gradient of the second order taken into consideration so as to characterize the effect of microstructure of the graphene sheet. Then, the RMS amplitude of thermalmore » vibration of a rectangular single-layered graphene sheet simply supported on an elastic foundation is derived. The study shows that the RMS amplitude of the rectangular single-layered graphene sheet predicted from the quantum theory is lower than that predicted from the law of energy equipartition. The maximal relative difference of RMS amplitude of thermal vibration appears at the sheet corners. The microstructure of the graphene sheet has a little effect on the thermal vibrations of lower modes, but exhibits an obvious effect on the thermal vibrations of higher modes. The quantum effect is more important for the thermal vibration of higher modes in the case of smaller sides and lower temperature. The relative difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet decreases monotonically with an increase of temperature. The absolute difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet increases slowly with the rising of Winkler foundation modulus.« less

Private States, Quantum Data Hiding, and the Swapping of Perfect Secrecy.

PubMed

Christandl, Matthias; Ferrara, Roberto

2017-12-01

An important contribution to the understanding of quantum key distribution has been the discovery of entangled states from which secret bits, but no maximally entangled states, can be extracted [Horodecki et al., Phys. Rev. Lett. 94, 200501 (2005)PRLTAO0031-900710.1103/PhysRevLett.94.200501]. The construction of those states was based on an intuition that the quantum mechanical phenomena of data hiding and privacy might be related. In this Letter we firmly connect these two phenomena and highlight three aspects of this result. First, we simplify the definition of the secret key rate. Second, we give a formula for the one-way distillable entanglement of certain private states. Third, we consider the problem of extending the distance of quantum key distribution with help of intermediate stations, a setting called the quantum key repeater. We show that for protocols that first distill private states, it is essentially optimal to use the standard quantum repeater protocol based on entanglement distillation and entanglement swapping.

Quantum centipedes: collective dynamics of interacting quantum walkers

NASA Astrophysics Data System (ADS)

Krapivsky, P. L.; Luck, J. M.; Mallick, K.

2016-08-01

We consider the quantum centipede made of N fermionic quantum walkers on the one-dimensional lattice interacting by means of the simplest of all hard-bound constraints: the distance between two consecutive fermions is either one or two lattice spacings. This composite quantum walker spreads ballistically, just as the simple quantum walk. However, because of the interactions between the internal degrees of freedom, the distribution of its center-of-mass velocity displays numerous ballistic fronts in the long-time limit, corresponding to singularities in the empirical velocity distribution. The spectrum of the centipede and the corresponding group velocities are analyzed by direct means for the first few values of N. Some analytical results are obtained for arbitrary N by exploiting an exact mapping of the problem onto a free-fermion system. We thus derive the maximal velocity describing the ballistic spreading of the two extremal fronts of the centipede wavefunction, including its non-trivial value in the large-N limit.

Computationally Efficient Nonlinear Bell Inequalities for Quantum Networks

NASA Astrophysics Data System (ADS)

Luo, Ming-Xing

2018-04-01

The correlations in quantum networks have attracted strong interest with new types of violations of the locality. The standard Bell inequalities cannot characterize the multipartite correlations that are generated by multiple sources. The main problem is that no computationally efficient method is available for constructing useful Bell inequalities for general quantum networks. In this work, we show a significant improvement by presenting new, explicit Bell-type inequalities for general networks including cyclic networks. These nonlinear inequalities are related to the matching problem of an equivalent unweighted bipartite graph that allows constructing a polynomial-time algorithm. For the quantum resources consisting of bipartite entangled pure states and generalized Greenberger-Horne-Zeilinger (GHZ) states, we prove the generic nonmultilocality of quantum networks with multiple independent observers using new Bell inequalities. The violations are maximal with respect to the presented Tsirelson's bound for Einstein-Podolsky-Rosen states and GHZ states. Moreover, these violations hold for Werner states or some general noisy states. Our results suggest that the presented Bell inequalities can be used to characterize experimental quantum networks.

Private States, Quantum Data Hiding, and the Swapping of Perfect Secrecy

NASA Astrophysics Data System (ADS)

Christandl, Matthias; Ferrara, Roberto

2017-12-01

An important contribution to the understanding of quantum key distribution has been the discovery of entangled states from which secret bits, but no maximally entangled states, can be extracted [Horodecki et al., Phys. Rev. Lett. 94, 200501 (2005), 10.1103/PhysRevLett.94.200501]. The construction of those states was based on an intuition that the quantum mechanical phenomena of data hiding and privacy might be related. In this Letter we firmly connect these two phenomena and highlight three aspects of this result. First, we simplify the definition of the secret key rate. Second, we give a formula for the one-way distillable entanglement of certain private states. Third, we consider the problem of extending the distance of quantum key distribution with help of intermediate stations, a setting called the quantum key repeater. We show that for protocols that first distill private states, it is essentially optimal to use the standard quantum repeater protocol based on entanglement distillation and entanglement swapping.

Thinning strategies for aspen: a prediction model.

Treesearch

Donald A. Perala

1978-01-01

Derives thinning strategies to maximize volume yields of aspen fiber, sawtimber, and veneer. Demonstrates how yields are affected by growing season climatic variation and periodic defoliation by forest tent caterpillar.

Photolysis of CH{sub 3}CHO at 248 nm: Evidence of triple fragmentation from primary quantum yield of CH{sub 3} and HCO radicals and H atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morajkar, Pranay; Schoemaecker, Coralie; Fittschen, Christa, E-mail: christa.fittschen@univ-lille1.fr

2014-06-07

Radical quantum yields have been measured following the 248 nm photolysis of acetaldehyde, CH{sub 3}CHO. HCO radical and H atom yields have been quantified by time resolved continuous wave Cavity Ring Down Spectroscopy in the near infrared following their conversion to HO{sub 2} radicals by reaction with O{sub 2}. The CH{sub 3} radical yield has been determined using the same technique following their conversion into CH{sub 3}O{sub 2}. Absolute yields have been deduced for HCO radicals and H atoms through fitting of time resolved HO{sub 2} profiles, obtained under various O{sub 2} concentrations, to a complex model, while the CH{submore » 3} yield has been determined relative to the CH{sub 3} yield from 248 nm photolysis of CH{sub 3}I. Time resolved HO{sub 2} profiles under very low O{sub 2} concentrations suggest that another unknown HO{sub 2} forming reaction path exists in this reaction system besides the conversion of HCO radicals and H atoms by reaction with O{sub 2}. HO{sub 2} profiles can be well reproduced under a large range of experimental conditions with the following quantum yields: CH{sub 3}CHO + hν{sub 248nm} → CH{sub 3}CHO{sup *}, CH{sub 3}CHO{sup *} → CH{sub 3} + HCO ϕ{sub 1a} = 0.125 ± 0.03, CH{sub 3}CHO{sup *} → CH{sub 3} + H + CO ϕ{sub 1e} = 0.205 ± 0.04, CH{sub 3}CHO{sup *}→{sup o{sub 2}}CH{sub 3}CO + HO{sub 2} ϕ{sub 1f} = 0.07 ± 0.01. The CH{sub 3}O{sub 2} quantum yield has been determined in separate experiments as ϕ{sub CH{sub 3}} = 0.33 ± 0.03 and is in excellent agreement with the CH{sub 3} yields derived from the HO{sub 2} measurements considering that the triple fragmentation (R1e) is an important reaction path in the 248 nm photolysis of CH{sub 3}CHO. From arithmetic considerations taking into account the HO{sub 2} and CH{sub 3} measurements we deduce a remaining quantum yield for the molecular pathway: CH{sub 3}CHO{sup *} → CH{sub 4} + CO ϕ{sub 1b} = 0.6. All experiments can be consistently explained with absence of the formerly considered pathway: CH{sub 3}CHO{sup *} → CH{sub 3}CO + H ϕ{sub 1c} = 0.« less

Green ultrasound-assisted extraction of anthocyanin and phenolic compounds from purple sweet potato using response surface methodology

NASA Astrophysics Data System (ADS)

Zhu, Zhenzhou; Guan, Qingyan; Guo, Ying; He, Jingren; Liu, Gang; Li, Shuyi; Barba, Francisco J.; Jaffrin, Michel Y.

2016-01-01

Response surface methodology was used to optimize experimental conditions for ultrasound-assisted extraction of valuable components (anthocyanins and phenolics) from purple sweet potatoes using water as a solvent. The Box-Behnken design was used for optimizing extraction responses of anthocyanin extraction yield, phenolic extraction yield, and specific energy consumption. Conditions to obtain maximal anthocyanin extraction yield, maximal phenolic extraction yield, and minimal specific energy consumption were different; an overall desirability function was used to search for overall optimal conditions: extraction temperature of 68ºC, ultrasonic treatment time of 52 min, and a liquid/solid ratio of 20. The optimized anthocyanin extraction yield, phenolic extraction yield, and specific energy consumption were 4.91 mg 100 g-1 fresh weight, 3.24 mg g-1 fresh weight, and 2.07 kWh g-1, respectively, with a desirability of 0.99. This study indicates that ultrasound-assisted extraction should contribute to a green process for valorization of purple sweet potatoes.

Establishing rational networking using the DL04 quantum secure direct communication protocol

NASA Astrophysics Data System (ADS)

Qin, Huawang; Tang, Wallace K. S.; Tso, Raylin

2018-06-01

The first rational quantum secure direct communication scheme is proposed, in which we use the game theory with incomplete information to model the rational behavior of the participant, and give the strategy space and utility function. The rational participant can get his maximal utility when he performs the protocol faithfully, and then the Nash equilibrium of the protocol can be achieved. Compared to the traditional schemes, our scheme will be more practical in the presence of rational participant.

Quantum Tomography via Compressed Sensing: Error Bounds, Sample Complexity and Efficient Estimators (Open Access, Publisher’s Version)

DTIC Science & Technology

2012-09-27

we require no entangling gates or ancillary systems for the procedure. In contrast with [19], our method is not restricted to processes that are...states, such as those recently developed for use with permutation-invariant states [60], matrix product states [61] or multi-scale entangled states [62...by adjoining an ancilla, preparing the maximally entangled state |ψ0〉, and applying E); then do compressed quantum state tomography on ρE ; see

Quantum key distribution with passive decoy state selection

NASA Astrophysics Data System (ADS)

Mauerer, Wolfgang; Silberhorn, Christine

2007-05-01

We propose a quantum key distribution scheme which closely matches the performance of a perfect single photon source. It nearly attains the physical upper bound in terms of key generation rate and maximally achievable distance. Our scheme relies on a practical setup based on a parametric downconversion source and present day, nonideal photon-number detection. Arbitrary experimental imperfections which lead to bit errors are included. We select decoy states by classical postprocessing. This allows one to improve the effective signal statistics and achievable distance.

Electron spin polarization by isospin ordering in correlated two-layer quantum Hall systems.

PubMed

Tiemann, L; Wegscheider, W; Hauser, M

2015-05-01

Enhancement of the electron spin polarization in a correlated two-layer, two-dimensional electron system at a total Landau level filling factor of 1 is reported. Using resistively detected nuclear magnetic resonance, we demonstrate that the electron spin polarization of two closely spaced two-dimensional electron systems becomes maximized when interlayer Coulomb correlations establish spontaneous isospin ferromagnetic order. This correlation-driven polarization dominates over the spin polarizations of competing single-layer fractional quantum Hall states under electron density imbalances.

Use of the fluorescence quantum yield for the determination of the number-average molecular weight of polymers of epicatechin with 4β→8 interflavin bonds

Treesearch

D. Cho; W.L. Mattice; L.J. Porter; Richard W. Hemingway

1989-01-01

Excitation at 280 nm produces a structureless emission band with a maximum at 321-324 nm for dilute solutions of catechin, epicatechin, and their oligomers in l,4-dioxane or water. The fluorescence quantum yield, Q, has been measured in these two solvents for five dimers, a trimer, a tetramer, a pentamer, a hexamer, and a polymer in which the monomer...

Photoisomerization of alfa calcidol by a sensitized quantum chain reaction.

PubMed

Estruch, Gastón A; Aramendía, Pedro F

2012-01-01

The production of vitamin D3 is a pharmaceutically relevant process, producing high added-value products. Precursors are extracts from vegetal origin but bearing mainly an E geometry in the 5,6 double bond. The synthesis of vitamin D3 (5-E-α-calcidol) with the correct Z stereochemistry in the 5,6 double bond from the E isomer using anthracene and triethylamine (TEA) as the sensitizer system was studied from the kinetic and mechanistic point of view. The sensitized isomerization of E-calcidol by irradiation of anthracene takes place only in deoxygenated solution and yields the Z isomer in ca 5% yield in the photostationary state. When TEA is added to the system, the E-Z reaction is not inhibited by oxygen any more, the quantum yield of photoisomerization to the Z isomer grows linearly with the concentration of E-calcidol, while conversions higher than 95% to the Z isomer are reached in the photostationary state and E-Z quantum yields as high as 45 at [E-calcidol] = 25 mM are reached. If TEA is replaced by 1,4-diazabicyclo[2.2.2]octane, the reaction rate drops to one-third at the same amine concentration. The observations can be explained by a quantum chain reaction mechanism. The high conversion achieved eliminates the need of isomer separation. © 2011 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia

2013-05-10

Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM)more » spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.« less

High Photoluminescence Quantum Yield in Band Gap Tunable Bromide Containing Mixed Halide Perovskites.

PubMed

Sutter-Fella, Carolin M; Li, Yanbo; Amani, Matin; Ager, Joel W; Toma, Francesca M; Yablonovitch, Eli; Sharp, Ian D; Javey, Ali

2016-01-13

Hybrid organic-inorganic halide perovskite based semiconductor materials are attractive for use in a wide range of optoelectronic devices because they combine the advantages of suitable optoelectronic attributes and simultaneously low-cost solution processability. Here, we present a two-step low-pressure vapor-assisted solution process to grow high quality homogeneous CH3NH3PbI3-xBrx perovskite films over the full band gap range of 1.6-2.3 eV. Photoluminescence light-in versus light-out characterization techniques are used to provide new insights into the optoelectronic properties of Br-containing hybrid organic-inorganic perovskites as a function of optical carrier injection by employing pump-powers over a 6 orders of magnitude dynamic range. The internal luminescence quantum yield of wide band gap perovskites reaches impressive values up to 30%. This high quantum yield translates into substantial quasi-Fermi level splitting and high "luminescence or optically implied" open-circuit voltage. Most importantly, both attributes, high internal quantum yield and high optically implied open-circuit voltage, are demonstrated over the entire band gap range (1.6 eV ≤ Eg ≤ 2.3 eV). These results establish the versatility of Br-containing perovskite semiconductors for a variety of applications and especially for the use as high-quality top cell in tandem photovoltaic devices in combination with industry dominant Si bottom cells.

Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols.

PubMed

Lee, Hyun Ji Julie; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A

2013-06-04

Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines, and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of water-soluble SOA generated from two monoterpenes, limonene and α-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ∼100 ppb ammonia in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (∼0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for λexcitation = 420 ± 50 nm and λemission = 475 ± 38 nm. The window of the strongest fluorescence shifted to λexcitation = 320 ± 25 nm and λemission = 425 ± 38 nm for the α-pinene-derived SOA. Both regions overlap with the EEM spectra of some of the fluorophores found in primary biological aerosols. Despite the low quantum yield, the aged SOA particles may have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

Synthesis of Nitrogen- and Chlorine-Doped Graphene Quantum Dots for Cancer Cell Imaging.

PubMed

Nafiujjaman, Md; Joon, Hwang; Kwak, Kwang Soo; Lee, Yong-Kyu

2018-06-01

In this study, we synthesized high quantum yield nitrogen and chlorine-doped graphene quantum dots (Cl-GQDs-N) for cancer cell imaging using simple and high production yield hydrothermal method from low-cost fructose. Prepared Cl-GQDs-N are about 30 nm in diameter and these Cl-GQDs-N display powerful blue color photoluminescence under the 365 nm UV lamp. We have further investigated their optical performances under various conditions. In vitro study shows no toxicity effect in normal and cancer cells treated with Cl-GQDs-N. Finally, we believe that our synthesized Cl-GQDs-N will bring more application opportunities in the field of bioimaging, optoelectronics and beyond.

State-selected chemical reaction dynamics at the S matrix level - Final-state specificities of near-threshold processes at low and high energies

NASA Technical Reports Server (NTRS)

Chatfield, David C.; Truhlar, Donald G.; Schwenke, David W.

1992-01-01

State-to-state reaction probabilities are found to be highly final-state specific at state-selected threshold energies for the reactions O + H2 yield OH + H and H + H2 yield H2 + H. The study includes initial rotational states with quantum numbers 0-15, and the specificity is especially dramatic for the more highly rotationally excited reactants. The analysis is based on accurate quantum mechanical reactive scattering calculations. Final-state specificity is shown in general to increase with the rotational quantum number of the reactant diatom, and the trends are confirmed for both zero and nonzero values of the total angular momentum.

Near-Unity Quantum Yields of Biexciton Emission from CdSe=CdS Nanocrystals Measured Using Single-Particle Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Young-Shin; Malko, Anton V.; Vela, Javier

2011-05-03

Biexciton photoluminescence (PL) quantum yields (Q 2X) of individual CdSe/CdS core-shell nanocrystal quantum dots with various shell thicknesses are derived from independent PL saturation and two-photon correlation measurements. We observe a near-unity Q{sub 2X} for some nanocrystals with an ultrathick 19-monolayer shell. High Q 2X’s are, however, not universal and vary widely among nominally identical nanocrystals indicating a significant dependence of Q 2X upon subtle structural differences. Interestingly, our measurements indicate that high Q 2X’s are not required to achieve complete suppression of PL intensity fluctuations in individual nanocrystals.

Stable CdS QDs with intense broadband photoluminescence and high quantum yields

NASA Astrophysics Data System (ADS)

Mandal, Abhijit; Saha, Jony; De, Goutam

2011-11-01

Aqueous synthesis of CdS quantum dots (QDs) using thiolactic acid (TLA) as a capping agent was reported. These QDs exhibited excellent colloidal and photostability over a span of 2 years and showed intense broadband and almost white photoluminescence suitable for solid state lighting devices. The photoluminescence (PL) property of the aqueous CdS QDs is optimized by adjusting various processing parameters. The highest quantum yield (QY) achieved for TLA capped CdS QDs of average size 3.5 nm was ˜50%. Luminescence lifetime measurements of CdS-TLA QDs indicated longer lifetimes and a larger contribution of the surface-related emission, indicating removal of quenching defects.

The initiating radical yields and the efficiency of polymerization for various dental photoinitiators excited by different light curing units.

PubMed

Neumann, Miguel G; Schmitt, Carla C; Ferreira, Giovana C; Corrêa, Ivo C

2006-06-01

To evaluate the efficiency of the photopolymerization of dental resins it is necessary to know to what extent the light emitted by the light curing units is absorbed by the photoinitiators. On the other hand, the efficiency of the absorbed photons to produce species that launch the polymerization process is also of paramount importance. Therefore, the previously determined PAE (photon absorption efficiency) is used in conjunction with the polymerization quantum yields for the photoinitiators, in order to be able to compare the total process on an equivalent basis. This parameter can be used to identify the best performance for the photochemical process with specific photoinitiators. The efficiency of LED (Ultrablue IS) and QTH (Optilux 401) lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). The extent of photopolymerization per absorbed photon was determined from the polymerization quantum yields obtained by using the photoinitiators to polymerize methyl methacrylate, and afterwards combined with the previously determined PAEs. Although CQ presents a rather low polymerization quantum yield, its photopolymerization efficiency is practically the highest when irradiated with the Ultrablue LED. On the other hand, Lucirin is much more efficient than the other photoinitiators when irradiated with a QTH lamp, due to its high quantum yield and the overlap between its absorption spectrum and the output of the visible lamp light. Difference in photopolymerization efficiencies arise when combinations of photoinitiators are used, and when LED sources are used in preference to QTH. Mechanistic understanding is essential to optimal initiator formulation.

Peptide-Decorated Tunable-Fluorescence Graphene Quantum Dots.

PubMed

Sapkota, Bedanga; Benabbas, Abdelkrim; Lin, Hao-Yu Greg; Liang, Wentao; Champion, Paul; Wanunu, Meni

2017-03-22

We report here the synthesis of graphene quantum dots with tunable size, surface chemistry, and fluorescence properties. In the size regime 15-35 nm, these quantum dots maintain strong visible light fluorescence (mean quantum yield of 0.64) and a high two-photon absorption (TPA) cross section (6500 Göppert-Mayer units). Furthermore, through noncovalent tailoring of the chemistry of these quantum dots, we obtain water-stable quantum dots. For example, quantum dots with lysine groups bind strongly to DNA in solution and inhibit polymerase-based DNA strand synthesis. Finally, by virtue of their mesoscopic size, the quantum dots exhibit good cell permeability into living epithelial cells, but they do not enter the cell nucleus.

Quantum entanglement at ambient conditions in a macroscopic solid-state spin ensemble.

PubMed

Klimov, Paul V; Falk, Abram L; Christle, David J; Dobrovitski, Viatcheslav V; Awschalom, David D

2015-11-01

Entanglement is a key resource for quantum computers, quantum-communication networks, and high-precision sensors. Macroscopic spin ensembles have been historically important in the development of quantum algorithms for these prospective technologies and remain strong candidates for implementing them today. This strength derives from their long-lived quantum coherence, strong signal, and ability to couple collectively to external degrees of freedom. Nonetheless, preparing ensembles of genuinely entangled spin states has required high magnetic fields and cryogenic temperatures or photochemical reactions. We demonstrate that entanglement can be realized in solid-state spin ensembles at ambient conditions. We use hybrid registers comprising of electron-nuclear spin pairs that are localized at color-center defects in a commercial SiC wafer. We optically initialize 10(3) identical registers in a 40-μm(3) volume (with [Formula: see text] fidelity) and deterministically prepare them into the maximally entangled Bell states (with 0.88 ± 0.07 fidelity). To verify entanglement, we develop a register-specific quantum-state tomography protocol. The entanglement of a macroscopic solid-state spin ensemble at ambient conditions represents an important step toward practical quantum technology.

Adaptive recurrence quantum entanglement distillation for two-Kraus-operator channels

NASA Astrophysics Data System (ADS)

Ruan, Liangzhong; Dai, Wenhan; Win, Moe Z.

2018-05-01

Quantum entanglement serves as a valuable resource for many important quantum operations. A pair of entangled qubits can be shared between two agents by first preparing a maximally entangled qubit pair at one agent, and then sending one of the qubits to the other agent through a quantum channel. In this process, the deterioration of entanglement is inevitable since the noise inherent in the channel contaminates the qubit. To address this challenge, various quantum entanglement distillation (QED) algorithms have been developed. Among them, recurrence algorithms have advantages in terms of implementability and robustness. However, the efficiency of recurrence QED algorithms has not been investigated thoroughly in the literature. This paper puts forth two recurrence QED algorithms that adapt to the quantum channel to tackle the efficiency issue. The proposed algorithms have guaranteed convergence for quantum channels with two Kraus operators, which include phase-damping and amplitude-damping channels. Analytical results show that the convergence speed of these algorithms is improved from linear to quadratic and one of the algorithms achieves the optimal speed. Numerical results confirm that the proposed algorithms significantly improve the efficiency of QED.

Collapse–revival of quantum discord and entanglement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Xue-Qun, E-mail: xqyan867@tom.com; Zhang, Bo-Ying

2014-10-15

In this paper the correlations dynamics of two atoms in the case of a micromaser-type system is investigated. Our results predict certain quasi-periodic collapse and revival phenomena for quantum discord and entanglement when the field is in Fock state and the two atoms are initially in maximally mixed state, which is a special separable state. Our calculations also show that the oscillations of the time evolution of both quantum discord and entanglement are almost in phase and they both have similar evolution behavior in some time range. The fact reveals the consistency of quantum discord and entanglement in some dynamicalmore » aspects. - Highlights: • The correlations dynamics of two atoms in the case of a micromaser-type system is investigated. • A quasi-periodic collapse and revival phenomenon for quantum discord and entanglement is reported. • A phenomenon of correlations revivals different from that of non-Markovian dynamics is revealed. • The oscillations of time evolution of both quantum discord and entanglement are almost in phase in our system. • Quantum discord and entanglement have similar evolution behavior in some time range.« less

What is dynamics in quantum gravity?

NASA Astrophysics Data System (ADS)

Małkiewicz, Przemysław

2017-10-01

The appearance of the Hamiltonian constraint in the canonical formalism for general relativity reflects the lack of a fixed external time. The dynamics of general relativistic systems can be expressed with respect to an arbitrarily chosen internal degree of freedom, the so-called internal clock. We investigate the way in which the choice of internal clock determines the quantum dynamics and how much different quantum dynamics induced by different clocks are. We develop our method of comparison by extending the Hamilton-Jacobi theory of contact transformations to include a new type of transformation which transforms both the canonical variables and the internal clock. We employ our method to study the quantum dynamics of the Friedmann-Lemaitre model and obtain semiclassical corrections to the classical dynamics, which depend on the choice of internal clock. For a unique quantisation map we find the abundance of inequivalent semiclassical corrections induced by quantum dynamics taking place in different internal clocks. It follows that the concepts like minimal volume, maximal curvature and the number of quantum bounces, often used to describe quantum effects in cosmological models, depend on the choice of internal clock.

Photochemical processes on Titan: Irradiation of mixtures of gases that simulate Titan's atmosphere

NASA Astrophysics Data System (ADS)

Tran, Buu N.; Joseph, Jeffrey C.; Force, Michael; Briggs, Robert G.; Vuitton, Veronique; Ferris, James P.

2005-09-01

Photochemical reaction pathways in Titan's atmosphere were investigated by irradiation of the individual components and the mixture containing nitrogen, methane, hydrogen, acetylene, ethylene, and cyanoacetylene. The quantum yields for the loss of the reactants and the formation of products were determined. Photolysis of ethylene yields mainly saturated compounds (ethane, propane, and butane) while photolysis of acetylene yields the same saturated compounds as well as ethylene and diacetylene. Irradiation of cyanoacetylene yields mainly hydrogen cyanide and small amounts of acetonitrile. When an amount of methane corresponding to its mixing ratio on Titan was added to these mixtures the quantum yields for the loss of reactants decreased and the quantum yields for hydrocarbon formation increased indicative of a hydrogen atom abstraction from methane by the photochemically generated radicals. GC/MS analysis of the products formed by irradiation of mixtures of all these gases generated over 120 compounds which were mainly aliphatic hydrocarbons containing double and triple bonds along with much smaller amounts of aromatic compounds like benzene, toluene and phenylacetylene. The reaction pathways were investigated by the use of 13C acetylene in these gas mixtures. No polycyclic aromatic compounds were detected. Vapor pressures of these compounds under conditions present in Titan's atmosphere were calculated. The low molecular weight compounds likely to be present in the atmosphere and aerosols of Titan as a result of photochemical processes are proposed.

From Maximization to Optimization: A Paradigm Shift in Rice Production in Thailand to Improve Overall Quality of Life of Stakeholders

PubMed Central

Doi, Ryoichi; Pitiwut, Supachai

2014-01-01

The concept of crop yield maximization has been widely supported. In practice, however, yield maximization does not necessarily lead to maximum socioeconomic welfare. Optimization is therefore necessary to ensure quality of life of farmers and other stakeholders. In Thailand, a rice farmers' network has adopted a promising agricultural system aimed at the optimization of rice farming. Various feasible techniques were flexibly combined. The new system offers technical strengths and minimizes certain difficulties with which the rice farmers once struggled. It has resulted in fairly good yields of up to 8.75 t ha−1 or yield increases of up to 57% (from 4.38 to 6.88 t ha−1). Under the optimization paradigm, the farmers have established diversified sustainable relationships with the paddy fields in terms of ecosystem management through their own self-motivated scientific observations. The system has resulted in good health conditions for the farmers and villagers, financial security, availability of extra time, and additional opportunities and freedom and hence in the improvement of their overall quality of life. The underlying technical and social mechanisms are discussed herein. PMID:25089294

Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network.

PubMed

Goto, Hayato

2016-02-22

The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence.

Bifurcation-based adiabatic quantum computation with a nonlinear oscillator network

NASA Astrophysics Data System (ADS)

Goto, Hayato

2016-02-01

The dynamics of nonlinear systems qualitatively change depending on their parameters, which is called bifurcation. A quantum-mechanical nonlinear oscillator can yield a quantum superposition of two oscillation states, known as a Schrödinger cat state, via quantum adiabatic evolution through its bifurcation point. Here we propose a quantum computer comprising such quantum nonlinear oscillators, instead of quantum bits, to solve hard combinatorial optimization problems. The nonlinear oscillator network finds optimal solutions via quantum adiabatic evolution, where nonlinear terms are increased slowly, in contrast to conventional adiabatic quantum computation or quantum annealing, where quantum fluctuation terms are decreased slowly. As a result of numerical simulations, it is concluded that quantum superposition and quantum fluctuation work effectively to find optimal solutions. It is also notable that the present computer is analogous to neural computers, which are also networks of nonlinear components. Thus, the present scheme will open new possibilities for quantum computation, nonlinear science, and artificial intelligence.

Can we Predict Quantum Yields Using Excited State Density Functional Theory for New Families of Fluorescent Dyes?

NASA Astrophysics Data System (ADS)

Kohn, Alexander W.; Lin, Zhou; Shepherd, James J.; Van Voorhis, Troy

2016-06-01

For a fluorescent dye, the quantum yield characterizes the efficiency of energy transfer from the absorbed light to the emitted fluorescence. In the screening among potential families of dyes, those with higher quantum yields are expected to have more advantages. From the perspective of theoreticians, an efficient prediction of the quantum yield using a universal excited state electronic structure theory is in demand but still challenging. The most representative examples for such excited state theory include time-dependent density functional theory (TDDFT) and restricted open-shell Kohn-Sham (ROKS). In the present study, we explore the possibility of predicting the quantum yields for conventional and new families of organic dyes using a combination of TDDFT and ROKS. We focus on radiative (kr) and nonradiative (knr) rates for the decay of the first singlet excited state (S_1) into the ground state (S_0) in accordance with Kasha's rule. M. Kasha, Discuss. Faraday Soc., 9, 14 (1950). For each dye compound, kr is calculated with the S_1-S_0 energy gap and transition dipole moment obtained using ROKS and TDDFT respectively at the relaxed S_1 geometry. Our predicted kr agrees well with the experimental value, so long as the order of energy levels is correctly predicted. Evaluation of knr is less straightforward as multiple processes are involved. Our study focuses on the S_1-T_1 intersystem crossing (ISC) and the S_1-S_0 internal conversion (IC): we investigate the properties that allow us to model the knr value using a Marcus-like expression, such as the Stokes shift, the reorganization energy, and the S_1-T_1 and S_1-S_0 energy gaps. Taking these factors into consideration, we compare our results with those obtained using the actual Marcus theory and provide explanation for discrepancy. T. Kowalczyk, T. Tsuchimochi, L. Top, P.-T. Chen, and T. Van Voorhis, J. Chem. Phys., 138, 164101 (2013). M. Kasha, Discuss. Faraday Soc., 9, 14 (1950).

Influence of Lumber Volume Maximization on Value in Sawing Hardwood Sawlogs

Treesearch

Philip H. Steele; Francis G. Wagner; Lalit Kumar; Philip A. Araman

1992-01-01

Research based on applying volume-maximizing sawing solutions to idealized hardwood log forms has shown that average lumber yield can be increased by 6 percent. It is possible, however, that a lumber volume-maximizing solution may result in a decrease in lumber grade and a net reduction in total value of sawn lumber. The objective of this study was to determine the...

Developing a Measure of General Academic Ability: An Application of Maximal Reliability and Optimal Linear Combination to High School Students' Scores

ERIC Educational Resources Information Center

Dimitrov, Dimiter M.; Raykov, Tenko; AL-Qataee, Abdullah Ali

2015-01-01

This article is concerned with developing a measure of general academic ability (GAA) for high school graduates who apply to colleges, as well as with the identification of optimal weights of the GAA indicators in a linear combination that yields a composite score with maximal reliability and maximal predictive validity, employing the framework of…

Effects of surface and interface traps on exciton and multi-exciton dynamics in core/shell quantum dots

NASA Astrophysics Data System (ADS)

Bozio, Renato; Righetto, Marcello; Minotto, Alessandro

2017-08-01

Exciton interactions and dynamics are the most important factors determining the exceptional photophysical properties of semiconductor quantum dots (QDs). In particular, best performances have been obtained for ingeniously engineered core/shell QDs. We have studied two factors entering in the exciton decay dynamics with adverse effects for the luminescence efficiency: exciton trapping at surface and interface traps, and non-radiative Auger recombination in QDs carrying either net charges or multiple excitons. In this work, we present a detailed study into the optical absorption, fluorescence dynamics and quantum yield, as well as ultrafast transient absorption properties of CdSe/CdS, CdSe/Cd0.5Zn0.5S, and CdSe/ZnS QDs as a function of shell thickness. It turns out that de-trapping processes play a pivotal role in determining steady state emission properties. By studying the excitation dependent photoluminescence quantum yields (PLQY) in different CdSe/CdxZn1-xS (x = 0, 0.5, 1) QDs, we demonstrate the different role played by hot and cold carrier trapping rates in determining fluorescence quantum yields. Finally, the use of global analysis allows us untangling the complex ultrafast transient absorption signals. Smoothing of interface potential, together with effective surface passivation, appear to be crucial factors in slowing down both Auger-based and exciton trapping recombination processes.

Photophysical properties gallium octacarboxy phthalocyanines conjugated to CdSe@ZnS quantum dots.

PubMed

Tshangana, Charmaine; Nyokong, Tebello

2015-01-01

L-Glutathione (GSH) capped core CdSe (2.3 nm) and core shell CdSe@ZnS quantum dots (QDs) (3.0 nm and 3.5 nm) were coordinated to gallium octacarboxy phthalocyanine (ClGaPc(COOH)8) to form ClGaPc(COOH)8-QDs conjugates. An efficient transfer of energy from the QDs to the Pcs was demonstrated through Förster resonance energy transfer (FRET), the FRET efficiencies in all cases was above 50%. The photophysical parameters (triplet state and fluorescence quantum yields and lifetimes) were also determined for the conjugates. There was a decrease in the fluorescence lifetimes of ClGaPc(COOH)8 in the presence of all the QDs, due to the heavy atom effect. The triplet quantum yields increased in the conjugates. The lifetimes also became longer for the conjugates compared to Pc alone. Copyright © 2015 Elsevier B.V. All rights reserved.

Luminescent carbon quantum dots with high quantum yield as a single white converter for white light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, X. T.; Zhang, Y.; Liu, X. G., E-mail: liuxuguang@tyut.edu.cn

Carbon quantum dots (CQDs) with high quantum yield (51.4%) were synthesized by a one-step hydrothermal method using thiosalicylic acid and ethylenediamine as precursor. The CQDs have the average diameter of 2.3 nm and possess excitation-independent emission wavelength in the range from 320 to 440 nm excitation. Under an ultraviolet (UV) excitation, the CQDs aqueous solutions emit bright blue fluorescence directly and exhibit broad emission with a high spectral component ratio of 67.4% (blue to red intensity to total intensity). We applied the CQDs as a single white-light converter for white light emitting diodes (WLEDs) using a UV-LED chip as the excitation lightmore » source. The resulted WLED shows superior performance with corresponding color temperature of 5227 K and the color coordinates of (0.34, 0.38) belonging to the white gamut.« less

Near-unity quantum yields from chloride treated CdTe colloidal quantum dots

DOE PAGES

Page, Robert C.; Espinobarro-Velazquez, Daniel; Leontiadou, Marina A.; ...

2014-10-27

Colloidal quantum dots (CQDs) are promising materials for novel light sources and solar energy conversion. However, trap states associated with the CQD surface can produce non-radiative charge recombination that significantly reduces device performance. Here a facile post-synthetic treatment of CdTe CQDs is demonstrated that uses chloride ions to achieve near-complete suppression of surface trapping, resulting in an increase of photoluminescence (PL) quantum yield (QY) from ca. 5% to up to 97.2 ± 2.5%. The effect of the treatment is characterised by absorption and PL spectroscopy, PL decay, scanning transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. We find thismore » process also dramatically improves the air-stability of the CQDs: before treatment the PL is largely quenched after 1 hour of air-exposure, whilst the treated samples showed a PL QY of nearly 50% after more than 12 hours.« less

Quantum Max-flow/Min-cut

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Shawn X., E-mail: xingshan@math.ucsb.edu; Quantum Architectures and Computation Group, Microsoft Research, Redmond, Washington 98052; Freedman, Michael H., E-mail: michaelf@microsoft.com

2016-06-15

The classical max-flow min-cut theorem describes transport through certain idealized classical networks. We consider the quantum analog for tensor networks. By associating an integral capacity to each edge and a tensor to each vertex in a flow network, we can also interpret it as a tensor network and, more specifically, as a linear map from the input space to the output space. The quantum max-flow is defined to be the maximal rank of this linear map over all choices of tensors. The quantum min-cut is defined to be the minimum product of the capacities of edges over all cuts ofmore » the tensor network. We show that unlike the classical case, the quantum max-flow=min-cut conjecture is not true in general. Under certain conditions, e.g., when the capacity on each edge is some power of a fixed integer, the quantum max-flow is proved to equal the quantum min-cut. However, concrete examples are also provided where the equality does not hold. We also found connections of quantum max-flow/min-cut with entropy of entanglement and the quantum satisfiability problem. We speculate that the phenomena revealed may be of interest both in spin systems in condensed matter and in quantum gravity.« less

Method for resurrecting negative electron affinity photocathodes after exposure to an oxidizing gas

DOEpatents

Mulhollan, Gregory A; Bierman, John C

2012-10-30

A method by which negative electron affinity photocathodes (201), single crystal, amorphous, or otherwise ordered, can be made to recover their quantum yield following exposure to an oxidizing gas has been discovered. Conventional recovery methods employ the use of cesium as a positive acting agent (104). In the improved recovery method, an electron beam (205), sufficiently energetic to generate a secondary electron cloud (207), is applied to the photocathode in need of recovery. The energetic beam, through the high secondary electron yield of the negative electron affinity surface (203), creates sufficient numbers of low energy electrons which act on the reduced-yield surface so as to negate the effects of absorbed oxidizing atoms thereby recovering the quantum yield to a pre-decay value.

Quantum walk on a chimera graph

NASA Astrophysics Data System (ADS)

Xu, Shu; Sun, Xiangxiang; Wu, Jizhou; Zhang, Wei-Wei; Arshed, Nigum; Sanders, Barry C.

2018-05-01

We analyse a continuous-time quantum walk on a chimera graph, which is a graph of choice for designing quantum annealers, and we discover beautiful quantum walk features such as localization that starkly distinguishes classical from quantum behaviour. Motivated by technological thrusts, we study continuous-time quantum walk on enhanced variants of the chimera graph and on diminished chimera graph with a random removal of vertices. We explain the quantum walk by constructing a generating set for a suitable subgroup of graph isomorphisms and corresponding symmetry operators that commute with the quantum walk Hamiltonian; the Hamiltonian and these symmetry operators provide a complete set of labels for the spectrum and the stationary states. Our quantum walk characterization of the chimera graph and its variants yields valuable insights into graphs used for designing quantum-annealers.

Quantum steering and entanglement in three-mode triangle Bose-Hubbard system

NASA Astrophysics Data System (ADS)

Kalaga, J. K.; Leoński, W.; Szczȩśniak, R.

2017-11-01

We consider the possibility of generation steerable states in Bose-Hubbard system composed of three interacting wells in the form of a triangle. We show that although our system still fulfills the monogamy relations, the presence of additional coupling which transforms a chain of wells onto triangle gives a variety of new possibilities for the generation of steerable quantum states. Deriving analytical formulas for the parameters describing steering and bipartite entanglement, we show that interplay between two couplings influences quantum correlations of various types. We compare the time evolution of steering parameters to those describing bipartite entanglement and find the relations between the appearance of maximal entanglement and disappearance of steering effect.

Convenient determination of luminescence quantum yield using a combined electronic absorption and emission spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prakash, John; Mishra, Ashok Kumar

2016-01-15

It is possible to measure luminescence quantum yield in a facile way, by designing an optical spectrometer capable of obtaining electronic absorption as well as luminescence spectra, with a setup that uses the same light source and detector for both the spectral measurements. Employment of a single light source and single detector enables use of the same correction factor profile for spectral corrections. A suitable instrumental scaling factor is used for adjusting spectral losses.

Production of NO2 from Photolysis of Peroxyacetyl Nitrate

NASA Technical Reports Server (NTRS)

Mazely, Troy L.; Friedl, Randall R.; Sander, Stanley P.

1965-01-01

Peroxyacetyl nitrate (PAN) vapor was photolyzed at 248 nm, and the NO2 photoproduct was detected by laser-induced fluorescence. The quantum yield for the production of NO2 from PAN photolysis was determined by comparison to HNO3 photolysis data taken under identical experimental conditions. The average of data collected over a range of total pressures, precursor concentrations, and buffer gases was 0.83 +/- 0.09 for the NO2 quantum yield, where the statistical uncertainty is 2 standard deviations.

Wakimoto realization of drinfeld current for the elliptic quantum algebra U{sub q,p}( widehat(sl{sub 3}) )

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kojima, T., E-mail: kojima@math.cst.nihon-u.ac.j

2010-02-15

We study a free field realization of the elliptic quantum algebra U{sub q,p}( widehat(sl{sub 3}) ) for arbitrary level k. We give the free field realization of elliptic analog of Drinfeld current associated with U{sub q,p}( widehat(sl{sub 3}) ) for arbitrary level k. In the limit p {yields} 0, q {yields} 1 our realization reproduces Wakimoto realization for the affine Lie algebra ( widehat(sl{sub 3}) ) .

Responses of photosynthetic properties and chloroplast ultrastructure of two moss crusts from a desert biological soil crust to supplementary UV-B radiation

NASA Astrophysics Data System (ADS)

Hui, Rong; Li, Xinrong; Zhao, Yang; Pan, Yanxia

2016-04-01

Our understanding of plant responses to supplementary ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion has improved over recent decades. However, research on biological soil crusts (BSCs) is scarce and it remains controversial. Laboratory studies were conducted to investigate the influence of UV-B radiation on the Bryum argenteum and Didymodon vinealis isolated from BSCs, which are both dominant species in moss crusts found within patches of shrubs and herbs in the Tengger Desert of northern China. The aim of the current work was to evaluate whether supplementary UV-B radiation affected photosynthetic properties and chloroplast ultrastructure of two moss crusts and whether response differences were observed between the crusts. Four levels of UV-B radiation of 2.75 (control), 3.08, 3.25, and 3.41 W m-2 was achieved using fluorescence tube systems for 10 days, simulating 0, 6, 9, and 12% of stratospheric ozone at the latitude of Shapotou, respectively. We measured photosynthetic apparatus as assessed by chlorophyll a fluorescence parameters, photosynthetic pigment contents, and observations of chloroplast ultrastructure. Additionally, soluble proteins and UV-B absorbing compounds were simultaneously investigated. The results of this study showed that chlorophyll a fluorescence parameters (i.e., the maximal quantum yield of PSII photochemistry, the effective quantum yield of PSII photochemistry, and photochemical quenching coefficient), photosynthetic pigment contents, soluble protein contents, total flavonoid contents and the ultrastructure were negatively influenced by elevated UV-B radiation and the degree of detrimental effects significantly increased with the intensity of UV-B radiation. Moreover, results demonstrated that the negative effects on photosynthesis and chloroplast ultrastructure were more serious in B. argenteum than that in D. vinealis. These results may not only provide a potential mechanism for supplemental UV-B effects on photosynthesis of moss crusts, but also establish a theoretical basis for further studies of adaptation and response mechanisms of desert ecosystems under further ozone depletion.

Different physiological and photosynthetic responses of three cyanobacterial strains to light and zinc.

PubMed

Xu, Kui; Juneau, Philippe

2016-01-01

Zinc pollution of freshwater aquatic ecosystems is a problem in many countries, although its specific effects on phytoplankton may be influenced by other environmental factors. Light intensity varies continuously under natural conditions depending on the cloud cover and the season, and the response mechanisms of cyanobacteria to high zinc stress under different light conditions are not yet well understood. We investigated the effects of high zinc concentrations on three cyanobacterial strains (Microcystis aeruginosa CPCC299, M. aeruginosa CPCC632, and Synechocystis sp. FACHB898) grown under two light regimes. Under high light condition (HL), the three cyanobacterial strains increased their Car/Chl a ratios and non-photochemical quenching (NPQ), with CPCC299 showing the highest growth rate-suggesting a greater ability to adapt to those conditions as compared to the other two strains. Under high zinc concentrations the values of maximal (ФM) and operational (Ф'M) photosystem II quantum yields, photosystem I quantum yield [Y(I)], and NPQ decreased. The following order of sensitivity to high zinc was established for the three strains studied: CPCC299>CPCC632>FACHB898. These different sensitivities can be partly explained by the higher internal zinc content observed in CPCC299 as compared to the other two strains. HL increased cellular zinc content and therefore increased zinc toxicity in both M. aeruginosa strains, although to a greater extent in CPCC299 than in CPCC632. Car/Chl a ratios decreased with high zinc concentrations under HL only in CPCC299, but not under low light (LL) conditions for all the studied strains, suggesting that the three strains have different response mechanisms to high zinc stress when grown under different light regimes. We demonstrated that interactions between light intensity and zinc need to be considered when studying the bloom dynamics of cyanobacteria in freshwater ecosystems. Copyright © 2015 Elsevier B.V. All rights reserved.

Protein-induced Photophysical Changes to the Amyloid Indicator Dye Thioflavin T

DOE Office of Scientific and Technical Information (OSTI.GOV)

L Wolfe; M Calabrese; A Nath

2011-12-31

The small molecule thioflavin T (ThT) is a defining probe for the identification and mechanistic study of amyloid fiber formation. As such, ThT is fundamental to investigations of serious diseases such as Alzheimer's disease, Parkinson disease, and type II diabetes. For each disease, a different protein undergoes conformational conversion to a {beta}-sheet rich fiber. The fluorescence of ThT exhibits an increase in quantum yield upon binding these fibers. Despite its widespread use, the structural basis for binding specificity and for the changes to the photophysical properties of ThT remain poorly understood. Here, we report the co-crystal structures of ThT withmore » two alternative states of {beta}-2 microglobulin ({beta}2m); one monomeric, the other an amyloid-like oligomer. In the latter, the dye intercalates between {beta}-sheets orthogonal to the {beta}-strands. Importantly, the fluorophore is bound in such a manner that a photophysically relevant torsion is limited to a range of angles generally associated with low, not high, quantum yield. Quantum mechanical assessment of the fluorophore shows the electronic distribution to be strongly stabilized by aromatic interactions with the protein. Monomeric {beta}2m gives little increase in ThT fluorescence despite showing three fluorophores, at two binding sites, in configurations generally associated with high quantum yield. Our efforts fundamentally extend existing understanding about the origins of amyloid-induced photophysical changes. Specifically, the {beta}-sheet interface that characterizes amyloid acts both sterically and electronically to stabilize the fluorophore's ground state electronic distribution. By preventing the fluorophore from adopting its preferred excited state configuration, nonradiative relaxation pathways are minimized and quantum yield is increased.« less

Protein-induced photophysical changes to the amyloid indicator dye thioflavin T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfe, Leslie S.; Calabrese, Matthew F.; Nath, Abhinav

2010-10-04

The small molecule thioflavin T (ThT) is a defining probe for the identification and mechanistic study of amyloid fiber formation. As such, ThT is fundamental to investigations of serious diseases such as Alzheimer's disease, Parkinson disease, and type II diabetes. For each disease, a different protein undergoes conformational conversion to a {beta}-sheet rich fiber. The fluorescence of ThT exhibits an increase in quantum yield upon binding these fibers. Despite its widespread use, the structural basis for binding specificity and for the changes to the photophysical properties of ThT remain poorly understood. Here, we report the co-crystal structures of ThT withmore » two alternative states of {beta}-2 microglobulin ({beta}2m); one monomeric, the other an amyloid-like oligomer. In the latter, the dye intercalates between {beta}-sheets orthogonal to the {beta}-strands. Importantly, the fluorophore is bound in such a manner that a photophysically relevant torsion is limited to a range of angles generally associated with low, not high, quantum yield. Quantum mechanical assessment of the fluorophore shows the electronic distribution to be strongly stabilized by aromatic interactions with the protein. Monomeric {beta}2m gives little increase in ThT fluorescence despite showing three fluorophores, at two binding sites, in configurations generally associated with high quantum yield. Our efforts fundamentally extend existing understanding about the origins of amyloid-induced photophysical changes. Specifically, the {beta}-sheet interface that characterizes amyloid acts both sterically and electronically to stabilize the fluorophore's ground state electronic distribution. By preventing the fluorophore from adopting its preferred excited state configuration, nonradiative relaxation pathways are minimized and quantum yield is increased.« less

Polarization entanglement purification of nonlocal microwave photons based on the cross-Kerr effect in circuit QED

NASA Astrophysics Data System (ADS)

Zhang, Hao; Liu, Qian; Xu, Xu-Sheng; Xiong, Jun; Alsaedi, Ahmed; Hayat, Tasawar; Deng, Fu-Guo

2017-11-01

Microwave photons have become very important qubits in quantum communication, as the first quantum satellite has been launched successfully. Therefore, it is a necessary and meaningful task for ensuring the high security and efficiency of microwave-based quantum communication in practice. Here, we present an original polarization entanglement purification protocol for nonlocal microwave photons based on the cross-Kerr effect in circuit quantum electrodynamics (QED). Our protocol can solve the problem that the purity of maximally entangled states used for constructing quantum channels will decrease due to decoherence from environment noise. This task is accomplished by means of the polarization parity-check quantum nondemolition (QND) detector, the bit-flipping operation, and the linear microwave elements. The QND detector is composed of several cross-Kerr effect systems which can be realized by coupling two superconducting transmission line resonators to a superconducting molecule with the N -type level structure. We give the applicable experimental parameters of QND measurement system in circuit QED and analyze the fidelities. Our protocol has good applications in long-distance quantum communication assisted by microwave photons in the future, such as satellite quantum communication.

Hybrid Molecule-Nanocrystal Photon Upconversion Across the Visible and Near-Infrared

DTIC Science & Technology

2015-07-10

applications in solar energy, biological imaging , and data storage. In this Letter, CdSe and PbSe semiconductor nanocrystals are combined with molecular...Goldschmidt, J. C. Absolute Upconversion Quantum Yield of β-NaYF4 Doped with Er3+ and External Quantum Efficiency of Upconverter Solar Cell Devices...C. Peak External Photocurrent Quantum Efficiency Exceeding 100% via MEG in a Quantum Dot Solar Cell . Science 2011, 334, 1530−1533. (37) Choi, J.-H

Aqueous synthesis of highly luminescent AgInS2-ZnS quantum dots and their biological applications

NASA Astrophysics Data System (ADS)

Regulacio, Michelle D.; Win, Khin Yin; Lo, Seong Loong; Zhang, Shuang-Yuan; Zhang, Xinhai; Wang, Shu; Han, Ming-Yong; Zheng, Yuangang

2013-02-01

Highly emissive and air-stable AgInS2-ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (>100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated.Highly emissive and air-stable AgInS2-ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (>100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated. Electronic supplementary information (ESI) available: Quantum yields, EDX spectrum and photoluminescence decay curves. See DOI: 10.1039/c3nr34159c

Measurement of Quantum Yield, Quantum Requirement, and Energetic Efficiency of the O2-Evolving System of Photosynthesis by a Simple Dye Reaction

NASA Astrophysics Data System (ADS)

Ros Barcelò, A.; Zapata, J. M.

1996-11-01

Photosynthesis is the conversion of absorbed radiant energy from sunlight into various forms of chemical energy by the chloroplasts of higher green plants. The overall process of photosynthesis consists of the oxidation of water (with the release of O2 as a product) and the reduction of CO2 to form carbohydrates. In the test tube electrons produced by the photolytic cleavage of H2) may be deviated from their true acceptor by inserting a suitable dye in the electron chain; i.e.; 2,6-dichlorophenol indophenol (DCPIP) (E'o = + 0.217 V), which is blue in the oxidized quinone form and which becomes colorless when reduced to the phenolic form. This dye-electrom acceptor also has the advantage that it accepts electroms directly from the quinone (Qa) electron-acceptor of the photosystem II< the reaction center associated with the O2-evolving (or water-slplitting) system. Based in the bleaching of DCPIP by illuminated spinach leaf chloroplasts, a classroom laboratory protocol has been developed to determine the quantum yield (QY = micromol O2 s-1 / micromol photons s-1, the quantum requirement (1/QY) and the energetic efficiency (f = chemical energy stored / light energy supplied) of the O2-evolving system of photosynthesis. Although values for the quantum yield, the quantum requirement and the energetic efficiency calculated in the classroom laboratory differ widely from those expected theoretically, these calculations are useful for illustrating the transformation of light energy into chemical energy by the chloroplasts of green plants.

Assisted Distillation of Quantum Coherence.

PubMed

Chitambar, E; Streltsov, A; Rana, S; Bera, M N; Adesso, G; Lewenstein, M

2016-02-19

We introduce and study the task of assisted coherence distillation. This task arises naturally in bipartite systems where both parties work together to generate the maximal possible coherence on one of the subsystems. Only incoherent operations are allowed on the target system, while general local quantum operations are permitted on the other; this is an operational paradigm that we call local quantum-incoherent operations and classical communication. We show that the asymptotic rate of assisted coherence distillation for pure states is equal to the coherence of assistance, an analog of the entanglement of assistance, whose properties we characterize. Our findings imply a novel interpretation of the von Neumann entropy: it quantifies the maximum amount of extra quantum coherence a system can gain when receiving assistance from a collaborative party. Our results are generalized to coherence localization in a multipartite setting and possible applications are discussed.

Number-unconstrained quantum sensing

NASA Astrophysics Data System (ADS)

Mitchell, Morgan W.

2017-12-01

Quantum sensing is commonly described as a constrained optimization problem: maximize the information gained about an unknown quantity using a limited number of particles. Important sensors including gravitational wave interferometers and some atomic sensors do not appear to fit this description, because there is no external constraint on particle number. Here, we develop the theory of particle-number-unconstrained quantum sensing, and describe how optimal particle numbers emerge from the competition of particle-environment and particle-particle interactions. We apply the theory to optical probing of an atomic medium modeled as a resonant, saturable absorber, and observe the emergence of well-defined finite optima without external constraints. The results contradict some expectations from number-constrained quantum sensing and show that probing with squeezed beams can give a large sensitivity advantage over classical strategies when each is optimized for particle number.

Strong Coupling Corrections in Quantum Thermodynamics

NASA Astrophysics Data System (ADS)

Perarnau-Llobet, M.; Wilming, H.; Riera, A.; Gallego, R.; Eisert, J.

2018-03-01

Quantum systems strongly coupled to many-body systems equilibrate to the reduced state of a global thermal state, deviating from the local thermal state of the system as it occurs in the weak-coupling limit. Taking this insight as a starting point, we study the thermodynamics of systems strongly coupled to thermal baths. First, we provide strong-coupling corrections to the second law applicable to general systems in three of its different readings: As a statement of maximal extractable work, on heat dissipation, and bound to the Carnot efficiency. These corrections become relevant for small quantum systems and vanish in first order in the interaction strength. We then move to the question of power of heat engines, obtaining a bound on the power enhancement due to strong coupling. Our results are exemplified on the paradigmatic non-Markovian quantum Brownian motion.

Quantum Discord for d⊗2 Systems

PubMed Central

Ma, Zhihao; Chen, Zhihua; Fanchini, Felipe Fernandes; Fei, Shao-Ming

2015-01-01

We present an analytical solution for classical correlation, defined in terms of linear entropy, in an arbitrary system when the second subsystem is measured. We show that the optimal measurements used in the maximization of the classical correlation in terms of linear entropy, when used to calculate the quantum discord in terms of von Neumann entropy, result in a tight upper bound for arbitrary systems. This bound agrees with all known analytical results about quantum discord in terms of von Neumann entropy and, when comparing it with the numerical results for 106 two-qubit random density matrices, we obtain an average deviation of order 10−4. Furthermore, our results give a way to calculate the quantum discord for arbitrary n-qubit GHZ and W states evolving under the action of the amplitude damping noisy channel. PMID:26036771

Transparent Ultra-High-Loading Quantum Dot/Polymer Nanocomposite Monolith for Gamma Scintillation.

PubMed

Liu, Chao; Li, Zhou; Hajagos, Tibor Jacob; Kishpaugh, David; Chen, Dustin Yuan; Pei, Qibing

2017-06-27

Spectroscopic gamma-photon detection has widespread applications for research, defense, and medical purposes. However, current commercial detectors are either prohibitively expensive for wide deployment or incapable of producing the characteristic gamma photopeak. Here we report the synthesis of transparent, ultra-high-loading (up to 60 wt %) Cd x Zn 1-x S/ZnS core/shell quantum dot/polymer nanocomposite monoliths for gamma scintillation by in situ copolymerization of the partially methacrylate-functionalized quantum dots in a monomer solution. The efficient Förster resonance energy transfer of the high-atomic-number quantum dots to lower-band-gap organic dyes enables the extraction of quantum-dot-borne excitons for photon production, resolving the problem of severe light yield deterioration found in previous nanoparticle-loaded scintillators. As a result, the nanocomposite scintillator exhibited simultaneous improvements in both light yield (visible photons produced per MeV of gamma-photon energy) and gamma attenuation. With these enhancements, a 662 keV Cs-137 gamma photopeak with 9.8% resolution has been detected using a 60 wt % quantum-dot nanocomposite scintillator, demonstrating the potential of such a nanocomposite system in the development of high-performance low-cost spectroscopic gamma detectors.

Homeotropic alignment and Förster resonance energy transfer: The way to a brighter luminescent solar concentrator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tummeltshammer, Clemens; Taylor, Alaric; Kenyon, Anthony J.

2014-11-07

We investigate homeotropically aligned fluorophores and Förster resonance energy transfer (FRET) for luminescent solar concentrators using Monte-Carlo ray tracing. The homeotropic alignment strongly improves the trapping efficiency, while FRET circumvents the low absorption at homeotropic alignment by separating the absorption and emission processes. We predict that this design doped with two organic dye molecules can yield a 82.9% optical efficiency improvement compared to a single, arbitrarily oriented dye molecule. We also show that quantum dots are prime candidates for absorption/donor fluorophores due to their wide absorption band. The potentially strong re-absorption and low quantum yield of quantum dots is notmore » a hindrance for this design.« less

Water catalysis and anticatalysis in photochemical reactions: observation of a delayed threshold effect in the reaction quantum yield.

PubMed

Kramer, Zeb C; Takahashi, Kaito; Skodje, Rex T

2010-11-03

The possible catalysis of photochemical reactions by water molecules is considered. Using theoretical simulations, we investigate the HF-elimination reaction of fluoromethanol in small water clusters initiated by the overtone excitation of the hydroxyl group. The reaction occurs in competition with the process of water evaporation that dissipates the excitation and quenches the reaction. Although the transition state barrier is stabilized by over 20 kcal/mol through hydrogen bonding with water, the quantum yield versus energy shows a pronounced delayed threshold that effectively eliminates the catalytic effect. It is concluded that the quantum chemistry calculations of barrier lowering are not sufficient to infer water catalysis in some photochemical reactions, which instead require dynamical modeling.

Templated self-assembly of quantum dots from aqueous solution using protein scaffolds

NASA Astrophysics Data System (ADS)

Szuchmacher Blum, Amy; Soto, Carissa M.; Wilson, Charmaine D.; Whitley, Jessica L.; Moore, Martin H.; Sapsford, Kim E.; Lin, Tianwei; Chatterji, Anju; Johnson, John E.; Ratna, Banahalli R.

2006-10-01

Short, histidine-containing peptides can be conjugated to lysine-containing protein scaffolds to controllably attach quantum dots (QDs) to the scaffold, allowing for generic attachment of quantum dots to any protein without the use of specially engineered domains. This technique was used to bind quantum dots from aqueous solution to both chicken IgG and cowpea mosaic virus (CPMV), a 30 nm viral particle. These quantum dot protein assemblies were studied in detail. The IgG QD complexes were shown to retain binding specificity to their antigen after modification. The CPMV QD complexes have a local concentration of quantum dots greater than 3000 nmol ml-1, and show a 15% increase in fluorescence quantum yield over free quantum dots in solution.

Synergistic Effects of Nano-Sized Titanium Dioxide and Zinc on the Photosynthetic Capacity and Survival of Anabaena sp.

PubMed Central

Tang, Yulin; Li, Shuyan; Qiao, Junlian; Wang, Hongtao; Li, Lei

2013-01-01

Anabaena sp. was used to examine the toxicity of exposure to a nano-TiO2 suspension, Zn2+ solution, and mixtures of nano-TiO2 and Zn2+ suspensions. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse-amplitude modulated fluorometer. Nano-TiO2 particles exhibited no significant toxicity at concentrations lower than 10.0 mg/L. The 96 h concentration for the 50% maximal effect (EC50) of Zn2+ alone to Anabaena sp. was 0.38 ± 0.004 mg/L. The presence of nano-TiO2 at low concentrations (<1.0 mg/L) significantly enhanced the toxicity of Zn2+ and consequently reduced the EC50 value to 0.29 ± 0.003 mg/L. However, the toxicity of the Zn2+/TiO2 system decreased with increasing nano-TiO2 concentration because of the substantial adsorption of Zn2+ by nano-TiO2. The toxicity curve of the Zn2+/TiO2 system as a function of incremental nano-TiO2 concentrations was parabolic. The toxicity significantly increased at the initial stage, reached its maximum, and then decreased with increasing nano-TiO2 concentration. Hydrodynamic sizes, concentration of nano-TiO2 and Zn2+ loaded nano-TiO2 were the main parameters for synergistic toxicity. PMID:23852017

High midday temperature stress has stronger effects on biomass than on photosynthesis: A mesocosm experiment on four tropical seagrass species.

PubMed

George, Rushingisha; Gullström, Martin; Mangora, Mwita M; Mtolera, Matern S P; Björk, Mats

2018-05-01

The effect of repeated midday temperature stress on the photosynthetic performance and biomass production of seagrass was studied in a mesocosm setup with four common tropical species, including Thalassia hemprichii , Cymodocea serrulata , Enhalus acoroides , and Thalassodendron ciliatum . To mimic natural conditions during low tides, the plants were exposed to temperature spikes of different maximal temperatures, that is, ambient (29-33°C), 34, 36, 40, and 45°C, during three midday hours for seven consecutive days. At temperatures of up to 36°C, all species could maintain full photosynthetic rates (measured as the electron transport rate, ETR) throughout the experiment without displaying any obvious photosynthetic stress responses (measured as declining maximal quantum yield, Fv/Fm). All species except T. ciliatum could also withstand 40°C, and only at 45°C did all species display significantly lower photosynthetic rates and declining Fv/Fm. Biomass estimation, however, revealed a different pattern, where significant losses of both above- and belowground seagrass biomass occurred in all species at both 40 and 45°C (except for C. serrulata in the 40°C treatment). Biomass losses were clearly higher in the shoots than in the belowground root-rhizome complex. The findings indicate that, although tropical seagrasses presently can cope with high midday temperature stress, a few degrees increase in maximum daily temperature could cause significant losses in seagrass biomass and productivity.

Bifunctional Diaminoterephthalate Fluorescent Dye as Probe for Cross-Linking Proteins.

PubMed

Wallisch, Melanie; Sulmann, Stefan; Koch, Karl-Wilhelm; Christoffers, Jens

2017-05-11

Diaminoterephthalates are fluorescent dyes and define scaffolds, which can be orthogonally functionalized at their two carboxylate residues with functional residues bearing task specific reactive groups. The synthesis of monofunctionalized dyes with thiol groups for surface binding, an azide for click chemistry, and a biotinoylated congener for streptavidin binding is reported. Two bifunctionalized dyes were prepared: One with an azide for click chemistry and a biotin for streptavidin binding, the other with a maleimide for reaction with thiol and a cyclooctyne moiety for ligation with copper-free click chemistry. In general, the compounds are red to orange, fluorescent materials with an absorption at about 450 nm and an emission at 560 nm with quantum yields between 2-41 %. Of particular interest is the maleimide-functionalized compound, which shows low fluorescence quantum yield (2 %) by itself. After addition of a thiol, the fluorescence is "turned on"; quantum yield 41 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A high quantum yield molecule-protein complex fluorophore for near-infrared II imaging

PubMed Central

Antaris, Alexander L.; Chen, Hao; Diao, Shuo; Ma, Zhuoran; Zhang, Zhe; Zhu, Shoujun; Wang, Joy; Lozano, Alexander X.; Fan, Quli; Chew, Leila; Zhu, Mark; Cheng, Kai; Hong, Xuechuan; Dai, Hongjie; Cheng, Zhen

2017-01-01

Fluorescence imaging in the second near-infrared window (NIR-II) allows visualization of deep anatomical features with an unprecedented degree of clarity. NIR-II fluorophores draw from a broad spectrum of materials spanning semiconducting nanomaterials to organic molecular dyes, yet unfortunately all water-soluble organic molecules with >1,000 nm emission suffer from low quantum yields that have limited temporal resolution and penetration depth. Here, we report tailoring the supramolecular assemblies of protein complexes with a sulfonated NIR-II organic dye (CH-4T) to produce a brilliant 110-fold increase in fluorescence, resulting in the highest quantum yield molecular fluorophore thus far. The bright molecular complex allowed for the fastest video-rate imaging in the second NIR window with ∼50-fold reduced exposure times at a fast 50 frames-per-second (FPS) capable of resolving mouse cardiac cycles. In addition, we demonstrate that the NIR-II molecular complexes are superior to clinically approved ICG for lymph node imaging deep within the mouse body. PMID:28524850

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filip, Radim; Marek, Petr; Fiurasek, Jaromir

We analyze a reversibility of optimal Gaussian 1{yields}2 quantum cloning of a coherent state using only local operations on the clones and classical communication between them and propose a feasible experimental test of this feature. Performing Bell-type homodyne measurement on one clone and anticlone, an arbitrary unknown input state (not only a coherent state) can be restored in the other clone by applying appropriate local unitary displacement operation. We generalize this concept to a partial reversal of the cloning using only local operations and classical communication (LOCC) and we show that this procedure converts the symmetric cloner to an asymmetricmore » cloner. Further, we discuss a distributed LOCC reversal in optimal 1{yields}M Gaussian cloning of coherent states which transforms it to optimal 1{yields}M{sup '} cloning for M{sup '}

Calculated quantum yield of photosynthesis of phytoplankton in the Marine Light-Mixed Layers (59 deg N, 21 deg W)

NASA Technical Reports Server (NTRS)

Carder, K. L.; Lee, Z. P.; Marra, John; Steward, R. G.; Perry, M. J.

1995-01-01

The quantum yield of photosynthesis (mol C/mol photons) was calculated at six depths for the waters of the Marine Light-Mixed Layer (MLML) cruise of May 1991. As there were photosynthetically available radiation (PAR) but no spectral irradiance measurements for the primary production incubations, three ways are presented here for the calculation of the absorbed photons (AP) by phytoplankton for the purpose of calculating phi. The first is based on a simple, nonspectral model; the second is based on a nonlinear regression using measured PAR values with depth; and the third is derived through remote sensing measurements. We show that the results of phi calculated using the nonlinear regreesion method and those using remote sensing are in good agreement with each other, and are consistent with the reported values of other studies. In deep waters, however, the simple nonspectral model may cause quantum yield values much higher than theoretically possible.

Photosensitized electron transport across lipid vesicle walls: Enhancement of quantum yield by ionophores and transmembrane potentials

PubMed Central

Laane, Colja; Ford, William E.; Otvos, John W.; Calvin, Melvin

1981-01-01

The photosensitized reduction of heptylviologen in the bulk aqueous phase of phosphatidylcholine vesicles containing EDTA inside and a membrane-bound tris(2,2′-bipyridine)ruthenium(2+) derivative is enhanced by a factor of 6.5 by the addition of valinomycin in the presence of K+. A 3-fold stimulation by gramicidin and carbonyl cyanide m-chlorophenylhydrazone is observed. The results suggest that, under these conditions, the rate of photoinduced electron transfer across vesicle walls in the absence of ion carriers is limited by cotransport of cations. The rate of electron transfer across vesicle walls could be influenced further by generating transmembrane potentials with K+ gradients in the presence of valinomycin. When vesicles are made with transmembrane potentials, interior more negative, the quantum yield of heptylviologen reduction is doubled, and, conversely, when vesicles are made with transmembrane potentials, interior more positive, the quantum yield is decreased and approaches the value found in the absence of valinomycin. PMID:16593002

Synthesis and spectroscopic properties of some new difluoroboron bis-β-diketonate derivatives.

PubMed

Pi, Yan; Wang, Dun-Jia; Liu, Hua; Hu, Yan-Jun; Wei, Xian-Hong; Zheng, Jing

2014-10-15

Six new bis-β-diketones (RCOCH2CO-C7H7N-COCH2COR) were synthesized from 3,5-diacetyl-2,6-dimethylpyridine via Claisen condensation with the corresponding esters, and then reacted with boron trifluoride etherate to afford difluoroboron bis-β-diketonate derivatives. Their spectroscopic properties were investigated by UV-vis, FTIR, (1)H NMR and fluorescence spectroscopic techniques. It was found that these boron complexes exhibited violet or blue fluorescence emission at 422-445nm and possessed high extinction coefficients. The results indicate that the extending π-conjugation can increase the fluorescence intensity and quantum yield for these boron complexes. Especially, the compound 2b displayed the stronger fluorescence intensity and the highest fluorescence quantum yield (Φu=0.94) in these boron compounds. However, compounds 2c and 2d had the lower fluorescence intensity and quantum yield as a result of the heavy atom effect of the chlorine atom in the molecules. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and spectroscopic properties of some new difluoroboron bis-β-diketonate derivatives

NASA Astrophysics Data System (ADS)

Pi, Yan; Wang, Dun-Jia; Liu, Hua; Hu, Yan-Jun; Wei, Xian-Hong; Zheng, Jing

2014-10-01

Six new bis-β-diketones (RCOCH2CO-C7H7N-COCH2COR) were synthesized from 3,5-diacetyl-2,6-dimethylpyridine via Claisen condensation with the corresponding esters, and then reacted with boron trifluoride etherate to afford difluoroboron bis-β-diketonate derivatives. Their spectroscopic properties were investigated by UV-vis, FTIR, 1H NMR and fluorescence spectroscopic techniques. It was found that these boron complexes exhibited violet or blue fluorescence emission at 422-445 nm and possessed high extinction coefficients. The results indicate that the extending π-conjugation can increase the fluorescence intensity and quantum yield for these boron complexes. Especially, the compound 2b displayed the stronger fluorescence intensity and the highest fluorescence quantum yield (Φu = 0.94) in these boron compounds. However, compounds 2c and 2d had the lower fluorescence intensity and quantum yield as a result of the heavy atom effect of the chlorine atom in the molecules.

Determination of apparent quantum yield spectra of DMS photo-degradation in an in situ iron-induced Northeast Pacific Ocean bloom

NASA Astrophysics Data System (ADS)

Bouillon, René-Christian; Miller, William L.

2004-03-01

The wavelength dependence of the photochemical removal efficiency for DMS was studied for samples from an iron-induced bloom in the Northeastern Pacific Ocean. In July 2002, a 64 km2 patch of ocean was iron-fertilized near Ocean Station Papa (50°12'N 144°45'W). Only small changes in pseudo-first-order apparent quantum yield (AQY*DMS(λ)) were observed outside the iron-patch. However, inside the patch, AQY*DMS(λ) decreased considerably over the two weeks following the initial iron injection. A positive strong correlation was found between pseudo-first-order apparent quantum yield determined at 330 nm (AQY*DMS(330 nm)) and NO3- concentrations. We propose that NO3--photolysis has a substantial influence on DMS photo-degradation rates in oceanic waters. This finding demonstrates that in addition to control DMS production, marine phytoplankton could indirectly influence the DMS photochemical loss rate via its control on NO3- distribution.

A high quantum yield molecule-protein complex fluorophore for near-infrared II imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antaris, Alexander L.; Chen, Hao; Diao, Shuo

Fluorescence imaging in the second near-infrared window (NIR-II) allows visualization of deep anatomical features with an unprecedented degree of clarity. NIR-II fluorophores draw from a broad spectrum of materials spanning semiconducting nanomaterials to organic molecular dyes, yet unfortunately all water-soluble organic molecules with 41,000 nm emission suffer from low quantum yields that have limited temporal resolution and penetration depth. We report tailoring the supramolecular assemblies of protein complexes with a sulfonated NIR-II organic dye (CH-4T) to produce a brilliant 110-fold increase in fluorescence, resulting in the highest quantum yield molecular fluorophore thus far. The bright molecular complex allowed for themore » fastest video-rate imaging in the second NIR window with B50-fold reduced exposure times at a fast 50 frames-per-second (FPS) capable of resolving mouse cardiac cycles. Additionally, we demonstrate that the NIR-II molecular complexes are superior to clinically approved ICG for lymph node imaging deep within the mouse body.« less

A high quantum yield molecule-protein complex fluorophore for near-infrared II imaging

DOE PAGES

Antaris, Alexander L.; Chen, Hao; Diao, Shuo; ...

2017-05-19

Fluorescence imaging in the second near-infrared window (NIR-II) allows visualization of deep anatomical features with an unprecedented degree of clarity. NIR-II fluorophores draw from a broad spectrum of materials spanning semiconducting nanomaterials to organic molecular dyes, yet unfortunately all water-soluble organic molecules with 41,000 nm emission suffer from low quantum yields that have limited temporal resolution and penetration depth. We report tailoring the supramolecular assemblies of protein complexes with a sulfonated NIR-II organic dye (CH-4T) to produce a brilliant 110-fold increase in fluorescence, resulting in the highest quantum yield molecular fluorophore thus far. The bright molecular complex allowed for themore » fastest video-rate imaging in the second NIR window with B50-fold reduced exposure times at a fast 50 frames-per-second (FPS) capable of resolving mouse cardiac cycles. Additionally, we demonstrate that the NIR-II molecular complexes are superior to clinically approved ICG for lymph node imaging deep within the mouse body.« less

[Optical and spectral parameters in Ce3+ -doped gadolinium gallium aluminum garnet glass-ceramics].

PubMed

Gong, Hua; Zhao, Xin; Yu, Xiao-bo; Setsuhisa, Tanabe; Lin, Hai

2010-01-01

The crystalline phases of Ce3+ -doped gadolinium gallium aluminum garnet (GGAG) glass-ceramics were investigated by X-ray diffraction, and the fluorescence spectra were recorded under the pumping of blue light-emitting diode (LED) using an integrating sphere of 10-inch in diameter, which connected to a CCD detector. The spectral power distribution of the glass-ceramics was obtained from the measured spectra first, and then the quantum yield was derived based on the photon distribution. The quantum yield of Ce3+ emission in GGAG glass-ceramics is 29.2%, meanwhile, the color coordinates and the correlated color temperature (CCT) of combined white light were proved to be x = 0.319, y = 0.349 and 6086 K, respectively. Although the quantum yield is a little smaller than the value in Ce3+ -doped YAG glass-ceramics, the CCT of the combined white light is much smaller than that in the latter. The optical behavior of GGAG glass-ceramics provides new vision for developing comfortable LED lighting devices.

Excitonic Emission of Monolayer Semiconductors Near-Field Coupled to High-Q Microresonators

NASA Astrophysics Data System (ADS)

Javerzac-Galy, Clément; Kumar, Anshuman; Schilling, Ryan D.; Piro, Nicolas; Khorasani, Sina; Barbone, Matteo; Goykhman, Ilya; Khurgin, Jacob B.; Ferrari, Andrea C.; Kippenberg, Tobias J.

2018-05-01

We present quantum yield measurements of single layer $\\textrm{WSe}_2$ (1L-$\\textrm{WSe}_2$) integrated with high-Q ($Q>10^6$) optical microdisk cavities, using an efficient ($\\eta>$90%) near-field coupling scheme based on a tapered optical fiber. Coupling of the excitonic emission is achieved by placing 1L-WSe$_2$ to the evanescent cavity field. This preserves the microresonator high intrinsic quality factor ($Q>10^6$) below the bandgap of 1L-WSe$_2$. The nonlinear excitation power dependence of the cavity quantum yield is in agreement with an exciton-exciton annihilation model. The cavity quantum yield is $\\textrm{QY}_\\textrm{c}\\sim10^{-3}$, consistent with operation in the \\textit{broad emitter} regime (i.e. the emission lifetime of 1L-WSe$_2$ is significantly shorter than the bare cavity decay time). This scheme can serve as a precise measurement tool for the excitonic emission of layered materials into cavity modes, for both in plane and out of plane excitation.

Improved sugar yields from biomass sorghum feedstocks: comparing low-lignin mutants and pretreatment chemistries

USDA-ARS?s Scientific Manuscript database

Background: For biofuel production processes to be economically efficient, it is essential to maximize the production of monomeric carbohydrates from the structural carbohydrates of feedstocks. One strategy for maximizing carbohydrate production is to identify less recalcitrant feedstock cultivars b...

Maximizing grain sorghum water use efficiency under deficit irrigation

USDA-ARS?s Scientific Manuscript database

Development and evaluation of sustainable and efficient irrigation strategies is a priority for producers faced with water shortages resulting from aquifer depletion, reduced base flows, and reallocation of water to non-agricultural sectors. Under a limited water supply, yield maximization may not b...

Teleportation of a 3-dimensional GHZ State

NASA Astrophysics Data System (ADS)

Cao, Hai-Jing; Wang, Huai-Sheng; Li, Peng-Fei; Song, He-Shan

2012-05-01

The process of teleportation of a completely unknown 3-dimensional GHZ state is considered. Three maximally entangled 3-dimensional Bell states function as quantum channel in the scheme. This teleportation scheme can be directly generalized to teleport an unknown d-dimensional GHZ state.

Hydroxyl Radical Fluorescence and Quantum Yield Following Lyman-α Photoexcitation of Water Vapor in a Room Temperature Cell and Cooled in a Supersonic Expansion.

PubMed

Young, Justin W; Booth, Ryan S; Vogelhuber, Kristen M; Stearns, Jaime A; Annesley, Christopher J

2018-06-28

Photoexcitation of water by Lyman-α (121.6 nm) induces a dissociation reaction that produces OH(A 2 Σ + ) + H. Despite this reaction being part of numerous studies, a combined understanding of the product and fluorescence yields is still lacking. Here, the rotational and vibrational distributions of OH(A) are determined from dispersed fluorescence following photoexcitation of both room-temperature and jet-cooled water vapor, for the first time in the same experiment. This work compares new data of state-resolved fluorescence with literature molecular branching ratios and brings previous studies into agreement through careful consideration of OH(A) fluorescent and predissociation lifetimes and confirms a fluorescent quantum yield of 8%. Comparison of the room-temperature and jet-cooled OH(A) populations indicate the temperature of H 2 O prior to excitation has subtle effects on the OH(A) population distribution, such as altering the rotational distribution in the ν' = 0 population and affecting the population in the ν' = 1 state. These results indicate jet-cooled water vapor may have a 1% higher fluorescence quantum yield compared to room-temperature water vapor.

Relative quantum yield of I-asterisk(2P1/2) in the tunable laser UV photodissociation of i-C3F7I and n-C3F7I - Effect of temperature and exciplex emission

NASA Technical Reports Server (NTRS)

Smedley, J. E.; Leone, S. R.

1983-01-01

Wavelength-specific relative quantum yields of metastable I from pulsed laser photodissociation of i-C3F7I and n-C3F7I in the range 265-336 nm are determined by measuring the time-resolved infrared emission from the atomic I(P-2(1/2) P-2(3/2) transition. It is shown that although this yield appears to be unity from 265 to 298 nm, it decreases dramatically at longer wavelengths. Values are also reported for the enhancement of emission from metastable I due to exciplex formation at several temperatures. The exciplex formation emission increases linearly with parent gas pressure, but decreases with increasing temperature. Absorption spectra of i- and n-C3F7I between 303 and 497 K are presented, and the effect of temperature on the quantum yields at selected wavelengths greater than 300 nm, where increasing the temperature enhances the absorption considerably, are given. The results are discussed in regard to the development of solar-pumped iodine lasers.

Increasing selectivity for TNT-based explosive detection by synchronous luminescence and derivative spectroscopy with quantum yields of selected aromatic amines.

PubMed

Sheaff, Chrystal N; Eastwood, Delyle; Wai, Chien M

2007-01-01

The detection of explosive material is at the forefront of current analytical problems. A detection method is desired that is not restricted to detecting only explosive materials, but is also capable of identifying the origin and type of explosive. It is essential that a detection method have the selectivity to distinguish among compounds in a mixture of explosives. The nitro compounds found in explosives have low fluorescent yields or are considered to be non-fluorescent; however, after reduction, the amino compounds exhibit relatively high fluorescence. We discuss how to increase selectivity of explosive detection using fluorescence; this includes synchronous luminescence and derivative spectroscopy with appropriate smoothing. By implementing synchronous luminescence and derivative spectroscopy, we were able to resolve the reduction products of one major TNT-based explosive compound, 2,4-diaminotoluene, and the reduction products of other minor TNT-based explosives in a mixture. We also report for the first time the quantum yields of these important compounds. Relative quantum yields are useful in establishing relative fluorescence intensities and are an important spectroscopic measurement of molecules. Our approach allows for rapid, sensitive, and selective detection with the discrimination necessary to distinguish among various explosives.

High Photoluminescence Quantum Yield in Band Gap Tunable Bromide Containing Mixed Halide Perovskites

DOE PAGES

Sutter-Fella, Carolin M.; Li, Yanbo; Amani, Matin; ...

2015-12-21

Hybrid organic-inorganic halide perovskite based semiconductor materials are attractive for use in a wide range of optoelectronic devices because they combine the advantages of suitable optoelectronic attributes and simultaneously low-cost solution processability. Here, we present a two-step low-pressure vapor-assisted solution process to grow high quality homogeneous CH 3NH 3PbI 3-xBr x perovskite films over the full band gap range of 1.6-2.3 eV. Photoluminescence light-in versus light-out characterization techniques are used to provide new insights into the optoelectronic properties of Br-containing hybrid organic-inorganic perovskites as a function of optical carrier injection by employing pump-powers over a 6 orders of magnitude dynamicmore » range. The internal luminescence quantum yield of wide band gap perovskites reaches impressive values up to 30%. This high quantum yield translates into substantial quasi-Fermi level splitting and high "luminescence or optically implied" open-circuit voltage. Most importantly, both attributes, high internal quantum yield and high optically implied open-circuit voltage, are demonstrated over the entire band gap range (1.6 eV ≤ E g ≤ 2.3 eV). These results establish the versatility of Br-containing perovskite semiconductors for a variety of applications and especially for the use as high-quality top cell in tandem photovoltaic devices in combination with industry dominant Si bottom cells. (Figure Presented).« less

Experimental implementation of local adiabatic evolution algorithms by an NMR quantum information processor.

PubMed

Mitra, Avik; Ghosh, Arindam; Das, Ranabir; Patel, Apoorva; Kumar, Anil

2005-12-01

Quantum adiabatic algorithm is a method of solving computational problems by evolving the ground state of a slowly varying Hamiltonian. The technique uses evolution of the ground state of a slowly varying Hamiltonian to reach the required output state. In some cases, such as the adiabatic versions of Grover's search algorithm and Deutsch-Jozsa algorithm, applying the global adiabatic evolution yields a complexity similar to their classical algorithms. However, using the local adiabatic evolution, the algorithms given by J. Roland and N.J. Cerf for Grover's search [J. Roland, N.J. Cerf, Quantum search by local adiabatic evolution, Phys. Rev. A 65 (2002) 042308] and by Saurya Das, Randy Kobes, and Gabor Kunstatter for the Deutsch-Jozsa algorithm [S. Das, R. Kobes, G. Kunstatter, Adiabatic quantum computation and Deutsh's algorithm, Phys. Rev. A 65 (2002) 062301], yield a complexity of order N (where N=2(n) and n is the number of qubits). In this paper, we report the experimental implementation of these local adiabatic evolution algorithms on a 2-qubit quantum information processor, by Nuclear Magnetic Resonance.

Giant electron-hole transport asymmetry in ultra-short quantum transistors.

PubMed

McRae, A C; Tayari, V; Porter, J M; Champagne, A R

2017-05-31

Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e-h charging energy asymmetry). We parameterize the e-h transport asymmetry by the ratio of the hole and electron charging energies η e-h . This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, η e-h reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV.

Observable measure of quantum coherence in finite dimensional systems.

PubMed

Girolami, Davide

2014-10-24

Quantum coherence is the key resource for quantum technology, with applications in quantum optics, information processing, metrology, and cryptography. Yet, there is no universally efficient method for quantifying coherence either in theoretical or in experimental practice. I introduce a framework for measuring quantum coherence in finite dimensional systems. I define a theoretical measure which satisfies the reliability criteria established in the context of quantum resource theories. Then, I present an experimental scheme implementable with current technology which evaluates the quantum coherence of an unknown state of a d-dimensional system by performing two programmable measurements on an ancillary qubit, in place of the O(d2) direct measurements required by full state reconstruction. The result yields a benchmark for monitoring quantum effects in complex systems, e.g., certifying nonclassicality in quantum protocols and probing the quantum behavior of biological complexes.

Primary photophysical properties of moxifloxacin--a fluoroquinolone antibiotic.

PubMed

Lorenzo, Fernando; Navaratnam, Suppiah; Edge, Ruth; Allen, Norman S

2008-01-01

The photophysical properties of the fluoroquinolone antibiotic moxifloxacin (MOX) were investigated in aqueous media. MOX in water, at pH 7.4, shows two intense absorption bands at 287 and 338 nm (epsilon = 44,000 and 17,000 dm(3) mol(-1) cm(-1), respectively). The absorption and emission properties of MOX are pH-dependent, pK(a) values for the protonation equilibria of both the ground (6.1 and 9.6) and excited singlet states (6.8 and 9.1) of MOX were determined spectroscopically. MOX fluoresces weakly, the quantum yield for fluorescence emission being maximum (0.07) at pH 8. Phosphorescence from the excited triplet state in frozen ethanol solution has a quantum yield of 0.046. Laser flash photolysis and pulse radiolysis studies have been carried out to characterize the transient species of MOX in aqueous solution. On laser excitation, MOX undergoes monophotonic photoionization with a quantum yield of 0.14. This leads to the formation of a long-lived cation radical whose absorption is maximum at 470 nm (epsilon(470) = 3400 dm(3) mol(-1) cm(-1)). The photoionization process releases hydrated electron which rapidly reacts (k = 2.8 x 10(10) dm(3) mol(-1) s(-1)) with ground state MOX, yielding a long-lived anion radical with maximum absorption at 390 nm (epsilon(390) = 2400 dm(3) mol(-1) cm(-1)). The cation radical of MOX is able to oxidize protein components tryptophan and tyrosine. The bimolecular rate constants for these reactions are 2.3 x 10(8) dm(3) mol(-1) s(-1) and 1.3 x 10(8) dm(3) mol(-1) s(-1), respectively. Singlet oxygen sensitized by the MOX triplet state was also detected only in oxygen-saturated D(2)O solutions, with a quantum yield of 0.075.