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Publications2024-03-27T15:21:11+01:00

Publications (2024)

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AutoQML: Automatic generation and training of robust quantum-inspired classifiers by using evolutionary algorithms on grayscale images

Authors: Altares-Lopez, Sergio; Garcia-Ripoll, Juan Jose; Ribeiro, Angela

Journal: EXPERT SYSTEMS WITH APPLICATIONS

Publication date: 2024/03/25

DOI: 10.1016/j.eswa.2023.122984

Abstract: A new hybrid system is proposed for automatically generating and training quantum-inspired classifiers on grayscale images by using multiobjective genetic algorithms. It is defined a dynamic fitness function to obtain the smallest circuit complexity and highest accuracy on unseen data, ensuring that the proposed technique is generalizable and robust. At the same time, it is minimized the complexity of the generated circuits in terms of the number of entangling operators by penalizing their appearance and number of gates. The size of the images is reduced by using two dimensionality reduction approaches: principal component analysis (PCA), which is encoded within the individual and genetically optimized by the system, and a small convolutional autoencoder (CAE). These two methods are compared with one another and with a classical nonlinear approach to understand their behaviors and to ensure that the classification ability is due to the quantum circuit and not the preprocessing technique used for dimensionality reduction.

Exploring Quantum Annealing Architectures: A Spin Glass Perspective

Authors: Jauma, Gabriel; Garcia-Ripoll, Juan Jose; Pino, Manuel

Journal: ADVANCED QUANTUM TECHNOLOGIES

Publication date: 2024/03/14

DOI: 10.1002/qute.202300245

Abstract: This work analyzes the spin-glass transition across various Ising models relevant to quantum annealers. By employing the parallel tempering method, the location of the spin-glass phase transition is extrapolated from the pseudo-critical temperature of finite-sized systems. The results confirm a spin-glass phase at finite temperature in random-regular and small-world graphs, in agreement with previous studies. However, strong evidence is obtained that this phase only occurs at zero temperature in the quasi-2D graphs of D-Wave, as their pseudo-critical temperature drifts toward zero. This implies that the asymptotic runtime to find the low-energy configuration of those graphs is likely to be polynomial in the size of the problem. Nevertheless, this scaling may only be reached for system sizes much larger than existing annealers, as the drift in the pseudo-critical temperature is slow. This slowness, together with an abrupt increase in thermalization times around the pseudo-critical temperature, may render the search for low-energy configurations with classical methods impractical. The search for quantum advantage with quantum annealers requires finding families of problems in which classical methods fail, leaving room for improvement. In search of these families and their characteristics, Ising problems with the topologies of D-Wave’s annealers are studied and a dichotomy is reconciled: in theory, they should be easy, but in practice, they are hard. image

Experimental and theoretical assessment of the enhanced hydrogen adsorption on polycyclic aromatic hydrocarbons upon decoration with alkali metals

Authors: Reider, Anna Maria; Kollotzek, Siegfried; Scheier, Paul; Calvo, Florent; Yurtsever, Ersin; Pirani, Fernando; Bartolomei, Massimiliano; Hernandez, Marta I.; Gonzalez-Lezana, Tomas; Campos-Martinez, Jose

Journal: INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

Publication date: 2024/03/08

DOI: 10.1016/j.ijhydene.2024.01.244

Abstract: Hydrogen storage by physisorption on carbon-based materials is limited by comparatively low adsorption energies. However, decoration of the carbon substrate with alkali, alkaline earth, or other metal atoms has been proposed as a means to enhance adsorption energies. The decoration affects also the stability of these materials since it makes them more stable and resilient in the repeated cycles of charge and discharge that would be required for a good material devoted to storage. We investigate hydrogen storage capacities of small polycyclic aromatic hydrocarbons (PAHs) cations grown in ultracold helium nanodroplets by analyzing the ion abundances and stabilities. The observations are assessed with quantum chemical calculations and atomistic simulations. It is experimentally shown that the addition of an alkali ion significantly enhances the hydrogen adsorption of the studied PAHs, up to 25% over the bare PAH in the experimental conditions studied here, and the simulations confirm this general trend except for some minor residual discrepancies in the special stabilities (magic numbers). Several approaches to study larger and different PAH compounds are also proposed, and for all cases it is found that alkali decoration increases energy stability by more than 100%.

Deconvolution of JWST/MIRI Images: Applications to an Active Galactic Nucleus Model and GATOS Observations of NGC 5728

Authors: Leist, M. T.; Packham, C.; Rosario, D. J. V.; Hope, D. A.; Alonso-Herrero, A.; Hicks, E. K. S.; Hoenig, S.; Zhang, L.; Davies, R.; Diaz-Santos, T.; Gonzalez-Martin, O.; Bellocchi, E.; Boorman, P. G.; Combes, F.; Garcia-Bernete, I.; Garcia-Burillo, S.; Garcia-Lorenzo, B.; Haidar, H.; Ichikawa, K.; Imanishi, M.; Jefferies, S. M.; Labiano, A.; Levenson, N. A.; Nikutta, R.; Pereira-Santaella, M.; Ramos Almeida, C.; Ricci, C.; Rigopoulou, D.; Schaefer, W.; Stalevski, M.; Ward, M. J.; Fuller, L.; Izumi, T.; Rouan, D.; Shimizu, T.

Journal: ASTRONOMICAL JOURNAL

Publication date: 2024/03/01

DOI: 10.3847/1538-3881/ad1886

Abstract: The superb image quality, stability, and sensitivity of JWST permit deconvolution techniques to be pursued with a fidelity unavailable to ground-based observations. We present an assessment of several deconvolution approaches to improve image quality and mitigate the effects of the complex JWST point-spread function (PSF). The optimal deconvolution method is determined by using WebbPSF to simulate JWST’s complex PSF and MIRISim to simulate multiband JWST/Mid-Infrared Imager Module (MIRIM) observations of a toy model of an active galactic nucleus (AGN). Five different deconvolution algorithms are tested: (1) Kraken deconvolution, (2) Richardson-Lucy, (3) the adaptive imaging deconvolution algorithm, (4) sparse regularization with the Condat-Vu algorithm, and (5) iterative Wiener filtering and thresholding. We find that Kraken affords the greatest FWHM reduction of the nuclear source of our MIRISim observations for the toy AGN model while retaining good photometric integrity across all simulated wave bands. Applying Kraken to Galactic Activity, Torus, and Outflow Survey (GATOS) multiband JWST/MIRIM observations of the Seyfert 2 galaxy NGC 5728, we find that the algorithm reduces the FWHM of the nuclear source by a factor of 1.6-2.2 across all five filters. Kraken images facilitate detection of extended nuclear emission similar to 2.” 5 (similar to 470 pc, position angle similar or equal to 115 degrees) in the SE-NW direction, especially at the longest wavelengths. We demonstrate that Kraken is a powerful tool to enhance faint features otherwise hidden in the complex JWST PSF.

Directional spontaneous emission in photonic crystal slabs

Authors: Navarro-Baron, Erik P.; Vinck-Posada, Herbert; Gonzalez-Tudela, Alejandro

Journal: NANOPHOTONICS

Publication date: 2024/02/25

DOI: 10.1515/nanoph-2023-0843

Abstract: Spontaneous emission is one of the most fundamental out-of-equilibrium processes in which an excited quantum emitter relaxes to the ground state due to quantum fluctuations. In this process, a photon is emitted that can interact with other nearby emitters and establish quantum correlations between them, e.g., via super and subradiance effects. One way to modify these photon-mediated interactions is to alter the dipole radiation patterns of the emitter, e.g., by placing photonic crystals near them. One recent example is the generation of strong directional emission patterns – key to enhancing super and subradiance effects – in two dimensions by employing photonic crystals with band structures characterized by linear isofrequency contours and saddle points. However, these studies have predominantly used oversimplified toy models, overlooking the electromagnetic field’s intricacies in actual materials, including aspects like geometrical dependencies, emitter positions, and polarization. Our study delves into the interaction between these directional emission patterns and the variables mentioned above, revealing the untapped potential to fine-tune collective quantum optical phenomena.

OH as a probe of the warm-water cycle in planet-forming disks

Authors: Zannese, Marion; Tabone, Benoit; Habart, Emilie; Goicoechea, Javier R.; Zanchet, Alexandre; van Dishoeck, Ewine F.; van Hemert, Marc C.; Black, John H.; Tielens, Alexander G. G. M.; Veselinova, A.; Jambrina, P. G.; Menendez, M.; Verdasco, E.; Aoiz, F. J.; Gonzalez-Sanchez, L.; Trahin, Boris; Dartois, Emmanuel; Berne, Olivier; Peeters, Els; He, Jinhua; Sidhu, Ameek; Chown, Ryan; Schroetter, Ilane; van de Putte, Dries; Canin, Amelie; Alarcon, Felipe; Abergel, Alain; Bergin, Edwin A.; Bernard-Salas, Jeronimo; Boersma, Christiaan; Bron, Emeric; Cami, Jan; Dicken, Daniel; Elyajouri, Meriem; Fuente, Asuncion; Gordon, Karl D.; Issa, Lina; Joblin, Christine; Kannavou, Olga; Khan, Baria; Languignon, David; Le Gal, Romane; Maragkoudakis, Alexandros; Meshaka, Raphael; Okada, Yoko; Onaka, Takashi; Pasquini, Sofia; Pound, Marc W.; Robberto, Massimo; Roellig, Markus; Schefter, Bethany; Schirmer, Thiebaut; Vicente, Silvia; Wolfire, Mark G.

Journal: NATURE ASTRONOMY

Publication date: 2024/02/23

DOI: 10.1038/s41550-024-02203-0

Abstract: Water is a key ingredient for the emergence of life as we know it. Yet, its destruction and reformation in space remain unprobed in warm gas (T > 300 K). Here we detect with the James Webb Space Telescope the emission of the hydroxyl radical (OH) from d203-506, a planet-forming disk exposed to external far-ultraviolet (FUV) radiation. These observations were made as part of the Early Release Science programme PDRs4All, which is focused on the Orion bar. The observed OH spectrum is compared with the results of quantum dynamical calculations to reveal two essential molecular processes. The highly excited rotational lines of OH in the mid-infrared are telltale signs of H2O destruction by FUV radiation. The OH rovibrational lines in the near-infrared are attributed to chemical excitation by the key reaction O + H-2 -> OH + H, which seeds the formation of water in the gas phase. These results show that under warm and irradiated conditions, water is destroyed and efficiently reformed through gas-phase reactions. We infer that, in this source, the equivalent of Earth oceans’ worth of water is destroyed per month and replenished. This warm-water cycle could reprocess some water inherited from cold interstellar clouds and explain the lower deuterium fraction of water in Earth’s oceans compared with that found around protostars.

A kernel-based machine learning potential and quantum vibrational state analysis of the cationic Ar hydride (Ar2H+)

Authors: Montes de Oca-Estevez, Maria Judit; Valdes, Alvaro; Prosmiti, Rita

Journal: PHYSICAL CHEMISTRY CHEMICAL PHYSICS

Publication date: 2024/02/22

DOI: 10.1039/d3cp05865d

Abstract: One of the most fascinating discoveries in recent years, in the cold and low pressure regions of the universe, was the detection of ArH+ and HeH+ species. The identification of such noble gas-containing molecules in space is the key to understanding noble gas chemistry. In the present work, we discuss the possibility of [Ar2H](+) existence as a potentially detectable molecule in the interstellar medium, providing new data on possible astronomical pathways and energetics of this compound. As a first step, a data-driven approach is proposed to construct a full 3D machine-learning potential energy surface (ML-PES) via the reproducing kernel Hilbert space (RKHS) method. The training and testing data sets are generated from CCSD(T)/CBS[56] computations, while a validation protocol is introduced to ensure the quality of the potential. In turn, the resulting ML-PES is employed to compute vibrational levels and molecular spectroscopic constants for the cation. In this way, the most common isotopologue in ISM, [(Ar2H)-Ar-36](+), was characterized for the first time, while simultaneously, comparisons with previously reported values available for [(Ar2H)-Ar-40](+) are discussed. Our present data could serve as a benchmark for future studies on this system, as well as on higher-order cationic Ar-hydrides of astrophysical interest.

Dynamical effects on the O(3P) + D2 reaction and its impact on the ?-doublet population

Authors: Veselinova, A.; Menendez, M.; Gonzalez-Sanchez, L.; Zanchet, A.; Aoiz, F. J.; Jambrina, P. G.

Journal: PHYSICAL CHEMISTRY CHEMICAL PHYSICS

Publication date: 2024/02/22

DOI: 10.1039/d3cp05510h

Abstract: The O(P-3) + D-2 -> OD((2)Pi) + D reaction presents the peculiarity of taking place on two different potential energy surfaces (PESs) of different symmetry, (3)A ‘ and (3)A ”, which become degenerate for collinear configurations where the saddle-point of the reaction is located. The degeneracy is broken for non-collinear approaches with the energy on the (3)A ‘ PES rising more abruptly with the bending angle, making the frequency of this mode higher on the (3)A ‘ state. Consequently, the (3)A ‘ PES should be less reactive than the (3)A ” one. Nevertheless, quantum scattering calculations show that the cross section is higher on the (3)A ‘ PES for energies close to the classical reaction threshold and rotationless reactant. It is found that the differences between the reactivity on the two PESs are greater for low values of total angular momentum, where the centrifugal barrier is lower and contribute to the higher population of the Pi(A ‘) Lambda-doublet states of OD at low collision energies. At high collision energies, the Pi(A ‘) Lambda-doublet state is also preferentially populated. Analysis of the differential cross sections reveals that the preponderance for the Pi(A ‘) Lambda-doublet at low energies comes from backward scattering, originating from the reaction on the (3)A ‘ PES, while at high energies, it proceeds from a different mechanism that leads to sideways scattering on the (3)A ” PES and that populates the Pi(A ‘) manifold.

Photodissociation of the CH2Br radical: A theoretical study

Authors: Charfeddine, F.; Zanchet, A.; Yazidi, O.; Cuevas, C. A.; Saiz-Lopez, A.; Banares, L.; Garcia-Vela, A.

Journal: JOURNAL OF CHEMICAL PHYSICS

Publication date: 2024/02/21

DOI: 10.1063/5.0187546

Abstract: Bromine atom (Br) reactions lead to ozone depletion in the troposphere and stratosphere. Photodegradation of bromocarbons is one of the main sources of bromine atoms in the atmosphere. Here, we use high-level ab initio methods, including spin-orbit effects, to study the photodissociation of the CH2Br radical. All possible fragmentation pathways, namely CH2Br + h nu -> CH2 + Br, HCBr + H, and CBr + H-2, have been analyzed. Potential-energy curves of the ground and several excited electronic states along the corresponding dissociating bond distance of each pathway have been calculated. Considering the actinic fluxes of solar irradiation in the troposphere and in the stratosphere in the relevant range of frequencies, it is found that the first five excited states of CH2Br can be accessed from the ground state. Analysis of the potential curves shows that the pathways producing CH2 + Br and HCBr + H can proceed through a fast direct dissociation mechanism, while the pathway leading to CBr + H-2 involves much slower dissociation mechanisms like internal conversion between electronic states, predissociation, or tunneling through exit barriers. The main implications are that the two faster channels are predicted to be dominant, and the slower pathway is expected to be less relevant. The tropospheric and stratospheric solar actinic fluxes also allow for further dissociation of the HCBr and CBr fragments, generating additional Br atoms, provided that they survive possible collisions with other atmospheric reagents. Finally, we discuss the possible effect of each of the three CH2Br dissociation pathways on the depletion of atmospheric ozone.

Indene energetic processing in ice mantles in the interstellar medium

Authors: Mate, Belen; Tanarro, Isabel; Pelaez, Ramon J.; Cernicharo, Jose; Herrero, Victor J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/02/16

DOI: 10.1051/0004-6361/202347889

Abstract: Context. Indene, a small PAH, has been detected in the gas phase in the cold dense cloud TMC-1. Due to the low temperature in the cloud, below indene condensation temperature, its presence in the ice mantles of dust grains is likely. Aims. The aim of this work is to study the stability of indene against the energetic processing by VUV photons or cosmic rays in the ice mantles of dense molecular clouds. Methods. Ice layers of pure indene or indene diluted in water ice were grown by vapor deposition on a cold surface held at 10 K, 100 K, or 140 K. The samples were processed with VUV photons (120-180 nm) and 5 keV electrons and the destruction of indene was monitored by following the decay of its absorption bands in the infrared (IR) spectrum. Finally, we recorded the mass spectra of the decomposition products sublimated by thermal programmed desorption of the processed samples. Results. Photolysis and radiolysis cross-sections, along with half-life energy doses for indene in the solid form and diluted in water ice matrices at 10 K were derived. Ketones and alcohols were identified as the main processing products in indene and water-ice mixtures Conclusions. Dilution in water ice enhances the destruction rate of indene under energetic processing. The molecule is expected to survive for more than 10(7) yr in the ice mantles of grains in the interior of dense clouds, but it will end up getting destroyed within the next few hundred years by the intense VUV field in the diffuse region at the edges of the cloud.

Doubly substituted isotopologues of HCCCN in TMC-1: Detection of D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N

Authors: Tercero, B.; Marcelino, N.; Roue, E.; Agundez, M.; Cabezas, C.; Fuentetaja, R.; de Vicente, P.; Cernicharo, J.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/02/09

DOI: 10.1051/0004-6361/202348929

Abstract: We report the first detection in space of a complete sample of nine doubly substituted isotopologues of HCCCN towards the cyanopolyyne peak of TMC-1 using observations of the QUIJOTE1 line survey taken with the Yebes 40m telescope. We detected (DCCCN)-C-13, (DCCCN)-C-13, (DCCCN)-C-13, (DCCCN)-N-15, (HCCCN)-C-13-C-13, (HCCCN)-C-13-C-13, (HCCCN)-C-13-C-13, (HCCCN)-C-13-N-15, and (HCCCN)-C-13-N-15 through their J = 4-3 and J = 5-4 lines in the 7mm window. In addition, we present an extensive analysis of the emission of HCCCN and its singly substituted isotopologues through a large velocity gradient model of the lines detected at 7mm and 3mm using the Yebes 40m and the IRAM 30m telescopes, respectively. The derived column densities for all the isotopologues are consistent in the two spectral bands for an H-2 volume density of 1 x 10(4) cm(-3) and a kinetic temperature of 10 K. Whereas we observed a C-13 fractionation for (HCCCN)-C-13 and other double isotopologues with a 13C atom adjacent to the nitrogen atom, we derived similar C/C-13 abundance ratios for the three 1(3)C substituted species of DCCCN. This suggests additional chemical discrimination for deuterated isotopologues of HCCCN. Finally, we present the spatial distribution of the J = 4-3 and J = 5-4 lines from the singly substituted species observed with the Yebes 40m telescope. The emission peak of the spatial distribution of DCCCN appears to be displaced by similar to 40 ” with respect to that of HCCCN and the C-13 and N-15 isotopologues. In addition to a di fferent formation route for the deuterated species, we could also expect that this di fferentiation owing to the deuterium fractionation is more e fficient at low temperatures, and therefore, that deuterated species trace a colder region of the cloud.

Study of the HCCNC and HNCCC isotopologs in TMC-1

Authors: Cernicharo, J.; Tercero, B.; Cabezas, C.; Agundez, M.; Roue, E.; Fuentetaja, R.; Marcelino, N.; de Vicente, P.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/02/09

DOI: 10.1051/0004-6361/202348822

Abstract: We present the detection of the three C-13 isotopologs of HCCNC and HNCCC toward TMC-1 using the QUIJOTE line survey. In addition, the D species has also been detected for these two isomers of HCCCN, whereas the N-15 isotopolog was only detected for HCCNC. Using high- J lines of HCCNC and HNCCC, we were able to derive very precise rotational temperatures, column densities, and subsequently the isotopic abundance ratios. We found that C-12/C-13 is similar to 90 for the three possible substitutions in both isomers. These results are slightly di fferent from what has been found for the most abundant isomer HCCCN, for which abundances of 105, 95, and 66 were found for each one of the three possible positions of 13C. The H/D abundance ratio was found to be 31 +/- 4 for HCCNC and of 53 +/- 6 for HNCCC. The latter is similar to the H/D abundance ratio derived for HCCCN (similar to 59). The N-14/N-15 isotopic abundance ratio in HCCNC is 243 +/- 24.

Minimal orthonormal bases for pure quantum state estimation

Authors: Zambrano, Leonardo; Pereira, Luciano; Delgado, Aldo

Journal: QUANTUM

Publication date: 2024/02/08

DOI:

Abstract: We present an analytical method to estimate pure quantum states using a minimum of three measurement bases in any finite -dimensional Hilbert space. This is optimal as two bases are insufficient to construct an informationally complete positive operator -valued measurement (ICPOVM) for pure states. We demonstrate our method using a binary tree structure, providing an algorithmic path for implementation. The performance of the method is evaluated through numerical simulations, showcasing its effectiveness for quantum state estimation.

Structures Of Dust and gAs (SODA): Constraining the innermost dust properties of II Zw96 with JWST observations of H2O and CO

Authors: Garcia-Bernete, I.; Pereira-Santaella, M.; Gonzalez-Alfonso, E.; Rigopoulou, D.; Efstathiou, A.; Donnan, F. R.; Thatte, N.

Journal: ASTRONOMY & ASTROPHYSICS

Publication date: 2024/02/01

DOI: 10.1051/0004-6361/202348744

Abstract: We analyze JWST NIRSpec+MIRI/MRS observations of the infrared (IR) gas-phase molecular bands of the most enshrouded source (D1) within the interacting system and luminous IR galaxy II Zw 096. We report the detection of rovibrational lines of H2O nu(2) = 1 – 0 (similar to 5.3-7.2 mu m) and (CO)-C-12 nu = 1 – 0 (similar to 4.45-4.95 mu m) in D1. The CO band shows the R- and P-branches in emission and the spectrum of the H2O band shows the P-branch in emission and the R-branch in absorption. The H2O R-branch in absorption unveils an IR-bright embedded compact source in D1 and the CO broad component features a highly turbulent environment. From both bands, we also identified extended intense star-forming (SF) activity associated with circumnuclear photodissociation regions (PDRs), consistent with the strong emission of the ionised 7.7 mu m polycyclic aromatic hydrocarbon band in this source. By including the 4.5-7.0 mu m continuum information derived from the H2O and CO analysis, we modelled the IR emission of D1 with a dusty torus and SF component. The torus is very compact (diameter of similar to 3 pc at 5 mu m) and characterised by warm dust (similar to 370 K), giving an IR surface brightness of similar to 3.6 x 10(8) L-circle dot pc(-2). This result suggests the presence of a dust-obscured active galactic nucleus (AGN) in D1, which has an exceptionally high covering factor that prevents the direct detection of AGN emission. Our results open a new way to investigate the physical conditions of inner dusty tori via modelling the observed IR molecular bands.

Impact of Early Coherences on the Control of Ultrafast Photodissociation Reactions

Authors: Arcos, Carlos G.; Garcia-Vela, Alberto; Sola, Ignacio R.

Journal: JOURNAL OF PHYSICAL CHEMISTRY LETTERS

Publication date: 2024/01/31

DOI: 10.1021/acs.jpclett.3c03430

Abstract: By coherent control, the yield of photodissociation reactions can be maximized, starting in a suitable superposition of vibrational states. In ultrafast processes, the interfering pathways are born from the early vibrational coherences in the ground electronic potential. We interpret their effect from a purely classical picture, in which the correlation between the initial position and momentum helps to synchronize the vibrational dynamics at the Franck-Condon window when the pulse is at its maximum intensity. In the quantum domain, we show that this localization in time and space is mediated by dynamic squeezing of the wave packet.

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