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At least 397 records · Page 22

Quantum-Inspired Maximizer

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).

Zak, Michail↗

Rigid rotators

The two-particle, steady-state Schroedinger equation is transformed to center of mass and internuclear distance vector coordinates, leading to the free particle wave equation for the kinetic energy motion of the molecule and a decoupled wave equation for a single particle of reduced mass moving in a spherical potential field. The latter describes the vibrational and rotational energy modes of the diatomic molecule. For fixed internuclear distance, this becomes the equation of rigid rotator motion. The classical partition function for the rotator is derived and compared with the quantum expression. Molecular symmetry effects are developed from the generalized Pauli principle that the steady-state wave function of any system of fundamental particles must be antisymmetric. Nuclear spin and spin quantum functions are introduced and ortho- and para-states of rotators, along with their degeneracies, are defined. Effects of nuclear spin on entropy are deduced. Next, rigid polyatomic rotators are considered and the partition function for this case is derived. The patterns of rotational energy levels for nonlinear molecules are discussed for the spherical symmetric top, for the prolate symmetric top, for the oblate symmetric top, and for the asymmetric top. Finally, the equilibrium energy and specific heat of rigid rotators are derived.

Source record↗

The Millimeter- and Submillimeter-Wave Spectrum of Gauche-Ethyl Alcohol

We report an investigation of the rotational-torsional spectrum of the gauche rotational isomers of ethyl alcohol in the 51-505 GHz frequency region. Over a thousand transitions between rotational levels in the gauche substates of the ground OH torsional state have been measured and assigned. These transitions involve rotational quantum numbers J and K(sub a) up to 30 and 15, respectively, and are of two types: alpha-type transitions between levels in either the gauche+ or the gauche-substate, and c-type transitions between rotational levels in the different substates. The majority of these transitions have been fit satisfactorily using a two-state Hamiltonian based on the Fixed Framework Axis Method (FFAM). The rotation, distortion, and interaction constants have been determined along with the energy difference between the two gauche substates. The derived constants can be used to predict many more transitions accurately for astronomical purposes. The J and K(sub a) region where the two-state analysis can be used has been determined. The basis for a three-state analysis including the trans substate is presented and the applicability of the FFAM approach is discussed.

Pearson, J. C.↗

On Benchmarking Quantum Heuristics

Present an outline of important aspects for benchmarking quantum algorithms, in particular quantum heuristics. Using quantum approximate optimization algorithm as an example, we demonstrate how the choice of cost Hamiltonian, of mixer, and of initial states can affect the performance. We also discuss how realistic aspects of near-term quantum hardware will influence the algorithm performance.

Wang, Zhihui↗

Comparison of cross sections from the quasi-classical trajectory method and the j(z)-conserving centrifugal sudden approximation with accurate quantum results for an atom-rigid nonlinear polyatomic collision

We report the results of a series of calculations of state-to-state integral cross sections for collisions between O and nonvibrating H2O in the gas phase on a model nonreactive potential energy surface. The dynamical methods used include converged quantum mechanical scattering calculations, the j(z) conserving centrifugal sudden (j(z)-CCS) approximation, and quasi-classical trajectory (QCT) calculations. We consider three total energies 0.001, 0.002, and 0.005 E(h) and the nine initial states with rotational angular momentum less than or equal to 2 (h/2 pi). The j(z)-CCS approximation gives good results, while the QCT method can be quite unreliable for transitions to specific rotational sublevels. However, the QCT cross sections summed over final sublevels and averaged over initial sublevels are in better agreement with the quantum results.

Schwenke, David W.↗

Quantitative absorption and fluorescence study of CO from 1060 to 1550 A

Measurement of the photoabsorption cross section of CO in the 1060-1550 A region using synchrotron radiation is described. The oscillator strengths for the transitions from CO (Chi1Sigma+ to various excited states are obtained from these data. Fluorescence from excited CO was observed in the 1150 to 3000 A and 3000 to 8000 A regions. The quantum yields for the production of fluroescence from the Alpha(1)P and B(1)Sigma(+) states are unity because their excitation energies are below the dissociation limit. The C(1)Sigma(+) , v = O level has significant fluorescence quantum yields both in the UV and visible region, but the yields for the E(1)Pi, v = O and C(1)Sigma(+), v = 1 levels are very small. The C(1)Sigma(+), v = 1 level is presumably predissociated. The cross sections for the production of fluroescence from the a'(3)Sigma(+), d(3)Delta sub 1, e(3)Sigma(-) yields a(3)Pi, and B(1)Sigma(+), C(1)Sigma(+) yields A(1)Pi transitions upon excitation from the X(1)Sigma(+) were measured.

Lee, L. C.↗

A Knowledge Graph Framework for Organizing Heterogeneous Datasets for Utilization in Classical and Quantum Computing: Current Challenges and Future Directions

"The escalating impact of climate change induced extreme weather events in urban, suburban, and rural environments demands a rethink of how we have been using the single event-based or use-case-based knowledge graph models. The lack of representation in interaction within environmental variables found in literature led to the development of a novel framework that reflects the true nature of the interconnectedness in our environment. We propose an Environmental Interaction Knowledge Graph (EIKG) framework. This general EIKG framework works as the basis for interconnected environmental events by knitting interrelated events such as hurricanes leading to storm surges, which lead to flood events that could cause mudslides, landslides, etc., The cascading nature of one event leading to another related event in the environment requires an adequate understanding of each event using contextual information before conducting any data-driven analytics. This vision paper showcases how the EIKG:floods, EIKG:wildfire EIKG:landslides, etc, can be derived from a base case framework of EIKG as those individual events are interconnected with some common denominator variables. As an example, the precipitation variable is used in the flood case study as well as in the wildfire case study, as excessive precipitation levels lead to floods, and lack of precipitation leads to droughts and wildfires. We identify the precipitation variable as a “common-denominator-variable” in extreme weather events that play a key role in modeling the environment leading to different extreme weather events based on the variability of that variable (varying values where low precipitation leads to drought, and high values lead to floods). We use the insights gained from EIKG to conduct classical and Quantum Machine Learning (QML) based data analysis on the research questions developed. Our preliminary study shows how the Variational Quantum Classifier (VQC) and Quantum Support Vector Classifier (QSVC) are used along with the classical machine learning models to compare the model accuracies. Our study elaborates on how a quantitative analysis uses state-of-the-art machine learning techniques that include implementing both classical and quantum machine learning models and developing the knowledge graph. The EIKG is used to organize heterogeneous datasets and integrate the relations to case-specific extreme weather events such as floods. The study uses datasets such as county-to-country residential mobility data, socioeconomic datasets from the US Census Bureau, climate and weather-related Earth Observational data from NASA, and critical infrastructure data from the Homeland Infrastructure datasets."

Knowledge Graphs, Quantum Computing, Heterogenous ↗

Infrared /IR/ spectroscopy in support of atmospheric measurements

In general, the data required for the more abundant species are: (1) linewidths as a function of temperature; (2) line strength measurements obtained at various temperatures when since quantum assignments for the lines are unknown the lower state energy levels are unknown; and (3) line strength measurements of the 'hot' bands and bands of the isotopic species. It is pointed out that an extensive list of line center frequencies and line strengths from 2400 to 3200 per cm of (CH4)4 has recently been added to the Air Force Geophysics Laboratory compilation. Since many of the lines in the list could not be assigned, the laboratory research required measurements of samples at various temperatures in order to experimentally determine the temperature dependence on the line strengths. The 'hot' band here refers to transitions arising from vibrational states other than the ground state. 'Hot' bands are usually near the parent band (arising from the ground state). Very few 'hot' bands are without parent bands.

Toth, R. A.↗

Fluorescence yields from photodissociation of OCS at 1060-1240 A

The cross sections for the production of fluorescence (3000-8000 A) from excited photofragments of OCS were determined in order to gain a better understanding of the role of carbonyl sulfide in interstellar photochemistry. Synchrotron radiation was used as the light source for the measurements in the 1060-1240 A region, as it is suitable for measuring the absorption cross section in the structured region. It was found that the quantum yields for the production of various CO triplet states are less than 1.5% at the observed excitation photon wavelengths.

Lee, L. C.↗

C-type transitions in methyl formate

Based on previously determined spectral constants for methyl formate in its ground torsional degenerate substate, the frequencies and intensities of forbidden c-type transitions in this molecule, which is represented by a large number of lines in OMC-1, are calculated along with other 'forbidden' transitions labeled x-type. The stronger c-type transitions below 300 GHz with angular momentum quantum number of 30 or less and with upper state rotational energy of 350/cm or less are included in a list of spectral frequencies presented in this paper. Because the c-type transitions borrow intensity from the b-type transitions, the intensities of strongly affected b-type spectra are recalculated and presented.

Plummer, Grant M.↗

Vibration-rotational intensities for the X 1Sigma(+) state of A1H and A1D

In the present calculation of vibrational-rotational line strengths for the ground electronic state of A1H and A1D, the vibrational and rotational quantum numbers used are respectively in the Delta-v zero-5 range for v-prime between zero and 15, and J-prime-J of + or - 1 for J-prime in the zero-50 range. The transition matrix elements were obtained on the basis of the Meyer and Rosmus (1975) ab initio dipole-moment function, together with the numerical vibrational-rotational energy function.

Tipping, R. H.↗

Benchmark calculations of thermal reaction rates. I - Quantal scattering theory

The thermal rate coefficient for the prototype reaction H + H2 yields H2 + H with zero total angular momentum is calculated by summing, averaging, and numerically integrating state-to-state reaction probabilities calculated by time-independent quantum-mechanical scattering theory. The results are very carefully converged with respect to all numerical parameters in order to provide high-precision benchmark results for confirming the accuracy of new methods and testing their efficiency.

Chatfield, David C.↗

Radiative transition probabilities for all vibrational levels in the X 1Sigma(+) state of HF

Recent analyses have led to an experimentally-based potential energy curve for the ground state of HF which includes nonadiabatic corrections and which joins smoothly to the long-range potential at an accurately determined dissociation limit. Using this potential curve and a new ab initio dipole moment function, accurate radiative transition probabilities among all vibrational levels of the ground state of HF have been calculated for selected rotational quantum numbers. Comparisons of Einstein A spontaneous emission coefficients, dipole moment absorption matrix elements, and Herman-Wallis factors for absorption bands are presented.

Zemke, Warren T.↗

Comparison of Oxygen Gauche Effects in Poly(Oxyethylene) and Poly(ethylene terephtylene) Based on Quantum Chemistry Calculations

The so-called oxygen gauche effect in poly(oxyethylene) (POE) and its model molecules such as 1,2-dimethoxyethane (DME) and diglyme (CH3OC2H4OC2H4OCH3) is manifested in the preference for gauche C-C bond conformations over trans. This has also been observed for poly(ethylene terephthalate) (PET). Our previous quantum chemistry calculations demonstrated that the large C-C gauche population in DME is due, in part, to a low-lying tg +/- g+ conformer that exhibits a substantial 1,5 CH ... O attraction. New calculations will be described that demonstrate the accuracy of the original quantum chemistry calculations. In addition, an extension of this work to model molecules for PET will be presented. It is seen that the C-C gauche preference is much stronger in 1,2 diacetoxyethane than in DME. In addition, there exist low-lying tg +/- g+/- and g+/-g+/-g+/- conformers that exhibit 1,5 CH ... O attractions involving the carbonyl oxygens. It is expected that the -O-C-C-O- torsional properties will be quite different in these two polymers. The quantum chemistry results are used to parameterize rotational isomeric states models (RIS) and force fields for molecular dynamics simulations of these polymers.

Jaffe, Richard↗

Spectroscopic Constants and Vibrational Frequencies for l-C3H+ and Isotopologues from Highly-Accurate Quartic Force Fields: The Detection of l-C3H+ in the Horsehead Nebula PDR Questioned

Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C3H+. In an effort to corroborate this finding, we employed state-of-the art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in the rotational transition energies resulting from this difference in D on the order of 1 MHz for the lowest observed transition (J = 4 yields 3) and growing as J increases, the assignment of the observed rotational lines from the Horsehead nebula to l-C3H+ is questionable.

ISM: individual objects↗

Initial Results from NASA’s Low-Cost Optical Terminal (LCOT) at Goddard Space Flight Center

We present the initial results from testing of the Low-Cost Optical Terminal (LCOT) at NASA-Goddard Space Flight Center (GSFC). LCOT is designed to be a single modular design that can be quickly reconfigured to support different laser communication missions. LCOT is built around a 70 cm commercially available telescope designed with optical and quantum communications in mind. We have installed a state-of-the-art adaptive optics system, novel high-power laser amplifiers, and other innovative subsystems developed by our team to facilitate laser communications. We have conducted tests of our LCOT system against operational space terminals, demonstrating our ability to receive a downlink and transmit an uplink. We show the results of these tests and give analysis of the results.

Laser communications↗

Initial Results from NASA’s Low-Cost Optical Terminal (LCOT) at Goddard Space Flight Center

We present the initial results from testing of the Low-Cost Optical Terminal (LCOT) at NASA-Goddard Space Flight Center (GSFC). LCOT is designed to be a single modular design that can be quickly reconfigured to support different laser communication missions. LCOT is built around a 70 cm commercially available telescope designed with optical and quantum communications in mind. We have installed a state-of-the-art adaptive optics system, novel high-power laser amplifiers, and other innovative subsystems developed by our team to facilitate laser communications. We have conducted tests of our LCOT system against operational space terminals, demonstrating our ability to receive a downlink and transmit an uplink. We show the results of these tests and give an analysis of the results.

Ground terminals↗