A generative modeling approach for benchmarking and training shallow quantum circuits

Hybrid quantum-classical algorithms provide ways to use noisy intermediate-scale quantum computers for practical applications. Expanding the portfolio of such techniques, we propose a quantum circuit learning algorithm that can be used to assist the characterization of quantum devices and to train shallow circuits for generative tasks. The procedure leverages quantum hardware capabilities to its fullest extent by using native gates and their qubit connectivity. We demonstrate that our approach can learn an optimal preparation of the Greenberger-Horne-Zeilinger states, also known as "cat states". We further demonstrate that our approach can efficiently prepare approximate representations of coherent thermal states, wave functions that encode Boltzmann probabilities in their amplitudes. Finally, complementing proposals to characterize the power or usefulness of near-term quantum devices, such as IBM's quantum volume, we provide a new hardware-independent metric called the qBAS score. It is based on the performance yield in a specific sampling task on one of the canonical machine learning data sets known as Bars and Stripes. We show how entanglement is a key ingredient in encoding the patterns of this data set; an ideal benchmark for testing hardware starting at four qubits and up. We provide experimental results and evaluation of this metric to probe the trade off between several architectural circuit designs and circuit depths on an ion-trap quantum computer.Comment: 16 pages, 9 figures. Minor revisions. As published in npj Quantum Informatio

A DFT insight into phenol adsorption on Mn-Ce oxide

Phenol, an important precursor for many industrial processes, is a nocive contaminant even at very low concentration because of its high toxicity and stability. Thus, its complete removal from wastewater becomes crucial and drives the search for catalysts that would efficiently adsorb and oxidize phenol molecules. Recently, Ce-Mn oxides catalytic performance was tested in phenol removal from water at 100 ºC, and atmospheric pressure. The results suggested the participation of MnOx species in this process, while DRIFTS spectra of Mn-Ce oxide sample indicated the formation of surface phenolate groups. However, the role of Ce and Mn cations during phenol adsorption on MnOx-CeO2 solid solutions is still not fully understood. Thus, in this work we performed ab-initio total energy calculations to evaluate the interactions of a phenol molecule on the 12.5% Mn-doped CeO2 (111) surface.Centro de Investigación y Desarrollo en Tecnología de Pintura

A first-principles modeling of Ni interactions on CeO2-ZrO 2 mixed oxide solid solutions

We performed DFT+U quantum period calculations to study the characteristics of Ni interactions on/in CeO2-ZrO2 mixed oxide solid solutions. We analyzed the energetics of Ni adsorption and insertion on/in different surface and subsurface sites of the Ce0.25Zr 0.75O2(111) slab, and also the changes in its atomic and electronic structures. The most stable interaction corresponds to a single Ni atom adsorbed on the O-O bridge site, where the nearest-neighbor metal atom is the Zr. Our calculations also show that Ni can form small clusters on the Ce0.75Zr0.25O2(111) surface; which also locate around the Zr dopant. Due to Ni interactions, surface and inner layers oxygen anions experience important modifications in their geometric positions and the Ni atom deposition results in the partial occupation of 7-coordinated Ce(4f) states. © 2011 American Chemical Society.Fil: Cova, Federico Hector. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; ArgentinaFil: Garcia Pintos, Delfina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; ArgentinaFil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Física; ArgentinaFil: Irigoyen, Beatriz del Luján. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; Argentin

Hydrodeoxygenation of Phenol to Benzene and Cyclohexane on Rh(111) and Rh(211) Surfaces: Insights from Density Functional Theory

Herein we describe the C–O cleavage of phenol and cyclohexanol over Rh(111) and Rh(211) surfaces using density functional theory calculations. Our analysis is complemented by a microkinetic model of the reactions, which indicates that the C–O bond cleavage of cyclohexanol is easier than that of phenol and that Rh(211) is more active than Rh(111) for both reactions. This indicates that phenol will react mainly following a pathway of initial hydrogenation to cyclohexanol followed by hydrodeoxygenation to cyclohexane. We show that there is a general relationship between the transition state and the final state of both C–O cleavage reactions, and that this relationship is the same for Rh(111) and Rh(211)

Adsorción de fenol sobre Ce<SUB>0,875</SUB>Mn<SUB>0,125</SUB>O<SUB>1,9375</SUB>(111): un estudio de primeros principios

El desarrollo de procesos eficientes para el tratamiento de los desechos industriales es crucial para evitar la contaminación del medio ambiente. Los efluentes líquidos provenientes de las industrias petroquímica, carboquímica, farmacéutica, del papel y de las pinturas contienen sustancias químicas tóxicas como el fenol, por lo que deben ser tratados previo a su descarga. El fenol es una sustancia muy nociva no sólo para los organismos acuáticos sino también para el ser humano. La elevada estabilidad de esta molécula dificulta su degradación con los métodos tradicionales de purificación de aguas, que además facilitan su reacción con el cloro y la formación de compuestos (clorofenoles) muy solubles y tóxicos. Recientemente se ha mostrado experimentalmente la elevada eficiencia del proceso de adsorción-oxidación catalítica del fenol sobre sólidos Ce-Mn-O, postulándose que esa molécula se adsorbe formando una especie fenolato [1]. Los cálculos de primeros principios pueden aportar información valiosa de las características y fenómenos físicoquímicos intervinientes en las interacciones del fenol sobre esos catalizadores. Entonces, en este trabajo se empleó la teoría del funcional de la densidad (DFT), para evaluar el comportamiento de los óxidos mixtos CeO2-MnO2 como adsorbentes del fenol.Centro de Investigación y Desarrollo en Ciencias AplicadasUniversidad de Buenos AiresUniversidad Nacional del Su