Publications (2023)
Total peer-reviewed articles: 111
Transmon-qubit readout using an in situ bifurcation amplification in the mesoscopic regime
Authors: Dassonneville, R.; Ramos, T.; Milchakov, V.; Mori, C.; Planat, L.; Foroughi, F.; Naud, C.; Hasch-Guichard, W.; Garcia-Ripoll, J. J.; Roch, N.; Buisson, O.
Journal: PHYSICAL REVIEW APPLIED
Publication date: 2023/10/19
DOI: 10.1103/PhysRevApplied.20.044050
Abstract: We demonstrate a transmon-qubit readout based on the nonlinear response to a drive of polaritonic meters in situ coupled to the qubit. Inside a three-dimensional readout cavity, we place a transmon molecule consisting of a transmon qubit and an ancilla mode interacting via nonperturbative cross-Kerr-coupling. The cavity couples strongly only to the ancilla mode, leading to hybridized lower and upper polaritonic meters. Both polaritons are anharmonic and dissipative, as they inherit a self-Kerr nonlinearity U from the ancilla and effective decay kappa from the open cavity. Via the ancilla, the polariton meters also inherit the nonperturbative cross-Kerr-coupling to the qubit. This results in a high qubit-dependent displacement 2 chi > kappa,U that can be read out via the cavity without causing Purcell decay. Moreover, the polariton meters, being nonlinear resonators, present bistability, and bifurcation behavior when the probing power increases. In this work, we focus on the bifurcation at low power in the few-photon regime, called the mesoscopic regime, which is accessible when the self-Kerr and decay rates of the polariton meter are similar, U similar to kappa. Capitalizing on a latching mechanism by bifurcation, the readout is sensitive to transmon-qubit relaxation error only in the first tens of nanoseconds. We thus report a single-shot fidelity of 98.6% while having an integration time of 500 ns and no requirement for an external quantum-limited amplifier.
Detection of a C4 Criegee Intermediate: Fourier-Transform Microwave Spectroscopy of Methacrolein Oxide
Authors: Endo, Yasuki; Chung, Chen-An; Witek, Henryk A.; Cabezas, Carlos; Lee, Yuan-Pern
Journal: JOURNAL OF PHYSICAL CHEMISTRY A
Publication date: 2023/10/10
Abstract: Pure rotational transitions of methacrolein oxide (MACRO) were observed by Fourier-transform microwave spectroscopy. Among the four low-lying conformers existing within an energy window of 3 kcal/mol, only the lowest-energy conformer, the anti-trans conformer, was detected in a discharged jet of a 1,3-diiode-2-methylprop-1-ene and O-2 mixture diluted in Ar. Nineteen pure rotational transitions, in the frequency range from 10 to 25 GHz, most of them showing A/E splitting due to the methyl-top internal rotation, were observed and analyzed by the XIAM program, yielding the internal rotation barrier of 559 cm(-1), which very well agrees with a theoretically calculated value, 558 cm(-1), at the CCSD(T)/cc-pVTZ level of theory.
Simulating supermassive black hole mass measurements for a sample of ultramassive galaxies using ELT/HARMONI high-spatial-resolution integral-field stellar kinematics
Authors: Nguyen, Dieu D.; Cappellari, Michele; Pereira-Santaella, Miguel
Journal: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Publication date: 2023/10/10
Abstract: As the earliest relics of star formation episodes of the Universe, the most massive galaxies are the key to our understanding of the stellar population, cosmic structure, and supermassive black hole (SMBH) evolution. However, the details of their formation histories remain uncertain. We address these problems by planning a large survey sample of 101 ultramassive galaxies (z <= 0.3, |delta + 24 degrees| < 45 degrees, |b| > 8 degrees), including 76 per cent ellipticals, 17 per cent lenticulars, and 7 per cent spirals brighter than M-K <= -27 mag (stellar mass 2 x 10(12) less than or similar to M-star less than or similar to 5 x 10(12) M-circle dot) with ELT/HARMONI. Our sample comprises diverse galaxy environments ranging from isolated to dense-cluster galaxies. The primary goals of the project are to (1) explore the stellar dynamics inside galaxy nuclei and weigh SMBHs, (2) constrain the black hole scaling relations at the highest mass, and (3) probe the late-time assembly of these most massive galaxies through the stellar population and kinematical gradients. We describe the survey, discuss the distinct demographics and environmental properties of the sample, and simulate their HARMONI I-z-, I-z + J-, and H + K-band observations by combining the inferred stellar-mass models from Pan-STARRS observations, an assumed synthetic spectrum of stars, and SMBHs with masses estimated based on different black hole scaling relations. Our simulations produce excellent state-of-the-art integral field spectrography and stellar kinematics (Delta V-rms less than or similar to 1.5 per cent) in a relatively short exposure time. We use these stellar kinematics in combination with the Jeans anisotropic model to reconstruct the SMBH mass and its error using a Markov chain Monte Carlo simulation. Thus, these simulations and modellings can be benchmarks to evaluate the instrument models and pipelines dedicated to HARMONI to exploit the unprecedented capabilities of ELT.
Computational Energy Spectra of the H2O@C70 Endofullerene
Authors: Carrillo-Bohorquez, Orlando; Valdes, Alvaro; Prosmiti, Rita
Journal: CHEMPHYSCHEM
Publication date: 2023/10/06
Abstract: A water molecule confined inside the C-70 fullerene was quantum-mechanically described using a computational approach within the MCTDH framework. Such procedure involves the development of a full-dimensional coupled hamiltonian, with an exact kinetic energy operator, including all rotational, translational and vibrational degrees of freedom of the endofullerene system. In turn, through an effective pairwise potential model, the ground and rotationally excited states of the encapsulated H2O inside the C-70 cage were calculated, and traced back to the isotropic case of the H2O@C-60 endofullerene in order to understand the nature and physical origin of the symmetry breaking observed experimentally in the latter system. Moreover, the computational scheme used here allows to study the quantization of the translational movement of the encapsulated water molecule inside the C-70 fullerene, and to investigate the confinement effects in the vibrational energy levels of the H2O@C-70 system.
Molecular Oxygen Trimer: Multiplet Structures and Stability
Authors: Castro-Gomez, L. Beatriz; Campos-Martinez, Jose; Hernandez, Marta I.; Hernandez-Lamoneda, Ramon
Journal: CHEMPHYSCHEM
Publication date: 2023/10/05
Abstract: We present a detailed theoretical study of the molecular oxygen trimer where the potential energy surfaces of the seven multiplet states have been calculated by means of a pair approximation with very accurate dimer ab initio potentials. In order to obtain all the states a matrix representation of the potential using the uncoupled spin representation has been applied. The S = 0 and S = 1 states are nearly degenerate and low-lying isomers appear for most multiplicities. A crucial point in deciding the relative stabilities is the zero-point energy which represents a sizable fraction of the electronic well-depth. Therefore, we have performed accurate diffusion Monte Carlo studies of the lowest state in each multiplicity. Analysis of the wavefunction allows a deeper interpretation of the cluster structures, finding that they are significantly floppy in most cases.
A High-level Ab Initio Study of the Destruction of Methanimine under UV Radiation
Authors: Bouallagui, A.; Zanchet, A.; Al Mogren, M. Mogren; Banares, L.; Garcia-Vela, A.
Journal: ASTROPHYSICAL JOURNAL
Publication date: 2023/10/01
Abstract: The photodecomposition of methanimine (CH2NH) in the interstellar medium through several possible pathways is investigated by means of high-level multireference configuration interaction ab initio calculations. Among these pathways are photodissociation pathways involving hydrogen-atom elimination from both the CH2 and NH groups, and fragmentation into CH2 and NH. Potential-energy curves for the ground and several excited electronic states, as well as nonadiabatic couplings between them, are calculated. Possible dissociation mechanisms are discussed for the different pathways. It is found that the minimum excitation energy required for methanimine dissociation is above 7 eV. By using a two-dimensional representation of methanimine, CH2NH -> CHNH2 isomerization is explored as an additional methanimine decomposition pathway. Hydrogen-atom elimination from the CH2 group is also investigated along the isomerization pathway. The results show that the isomerization proceeds by overcoming a transition state that in the first two excited states would require excitation energies similar to or somewhat lower than the typical minimum energies needed for breaking the molecule through the fragmentation pathways. Therefore, CH2NH -> CHNH2 isomerization can effectively contribute to methanimine decomposition, competing efficiently with the photodissociation pathways. The radiation content present in the interstellar medium makes possible the occurrence of all the pathways studied.
Improving quantum state transfer: correcting non-Markovian and distortion effects
Authors: Peñas, Guillermo F.; Puebla, Ricardo; Garcia-Ripoll, Juan Jose
Journal: QUANTUM SCIENCE AND TECHNOLOGY
Publication date: 2023/10/01
Abstract: Quantum state transfer is a key operation for quantum information processing. The original pitch-and-catch protocols rely on flying qubits or single photons with engineered wavepacket shapes to achieve a deterministic, fast and high-fidelity transfer. Yet, these protocols overlook two important factors, namely, the distortion of the wavepacket during the propagation and non-Markovian effects during the emission and reabsorption processes due to time-dependent controls. Here we address both difficulties in a general quantum-optical model and propose a correction strategy to improve quantum state transfer protocols. Including non-Markovian effects in our theoretical description, we show how to derive control pulses that imprint phases on the wavepacket that compensate the distortion caused by propagation. Our theoretical results are supported by detailed numerical simulations showing that a suitable correction strategy can improve state transfer fidelities up to three orders of magnitude.
Multiobjective variational quantum optimization for constrained problems: an application to cash handling
Authors: Diez-Valle, Pablo; Luis-Hita, Jorge; Hernandez-Santana, Senaida; Martinez-Garcia, Fernando; Diaz-Fernandez, Alvaro; Andres, Eva; Garcia-Ripoll, Juan Jose; Sanchez-Martinez, Escolastico; Porras, Diego
Journal: QUANTUM SCIENCE AND TECHNOLOGY
Publication date: 2023/10/01
Abstract: Combinatorial optimization problems are ubiquitous in industry. In addition to finding a solution with minimum cost, problems of high relevance involve a number of constraints that the solution must satisfy. Variational quantum algorithms (VQAs) have emerged as promising candidates for solving these problems in the noisy intermediate-scale quantum stage. However, the constraints are often complex enough to make their efficient mapping to quantum hardware difficult or even infeasible. An alternative standard approach is to transform the optimization problem to include these constraints as penalty terms, but this method involves additional hyperparameters and does not ensure that the constraints are satisfied due to the existence of local minima. In this paper, we introduce a new method for solving combinatorial optimization problems with challenging constraints using VQAs. We propose the multi-objective variational constrained optimizer (MOVCO) to classically update the variational parameters by a multiobjective optimization performed by a genetic algorithm. This optimization allows the algorithm to progressively sample only states within the in-constraints space, while optimizing the energy of these states. We test our proposal on a real-world problem with great relevance in finance: the cash handling problem. We introduce a novel mathematical formulation for this problem, and compare the performance of MOVCO versus a penalty based optimization. Our empirical results show a significant improvement in terms of the cost of the achieved solutions, but especially in the avoidance of local minima that do not satisfy any of the mandatory constraints.
Solvation of cationic copper clusters in molecular hydrogen
Authors: Lushchikova, O. V.; Reichegger, J.; Kollotzek, S.; Zappa, F.; Mahmoodi-Darian, M.; Bartolomei, M.; Campos-Martinez, J.; Gonzalez-Lezana, T.; Pirani, F.; Scheier, P.
Journal: PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Publication date: 2023/09/27
DOI: 10.1039/d3cp03452f
Abstract: Multiply charged superfluid helium nanodroplets are utilized to facilitate the growth of cationic copper clusters (Cun+, where n = 1-8) that are subsequently solvated with up to 50 H2 molecules. Production of both pristine and protonated cationic Cu clusters are detected mass spectrometrically. A joint effort between experiment and theory allows us to understand the nature of the interactions determining the bonding between pristine and protonated Cu+ and Cu2+ cations and molecular hydrogen. The analysis reveals that in all investigated cationic clusters, the primary solvation shell predominantly exhibits a covalent bonding character, which gradually decreases in strength, while for the subsequent shells an exclusive non-covalent behaviour is found. Interestingly, the calculated evaporation energies associated with the first solvation shell markedly surpass thermal values, positioning them within the desirable range for hydrogen storage applications. This comprehensive study not only provides insights into the solvation of pristine and protonated cationic Cu clusters but also sheds light on their unique bonding properties. We underscore a solid agreement between experimental and computational studies on solvation of pristine/protonated Cun+ (n = 1-2) in H2. For instance, with n = 1, the initial shell comprises four covalently bound H2; subsequent ones are non-covalent.
Detection of ethynylbenzene in TMC-1 and the interstellar search for 1,2-diethynylbenzene
Authors: Loru, Donatella; Cabezas, Carlos; Cernicharo, Jose; Schnell, Melanie; Steber, Amanda L.
Journal: ASTRONOMY & ASTROPHYSICS
Publication date: 2023/09/22
DOI: 10.1051/0004-6361/202347023
Abstract: Aims. We investigate the outcome of an electrical discharge of naphthalene and search for the resulting products in the Taurus Molecular Cloud (TMC-1).Methods. Using chirped pulse Fourier transform microwave spectroscopy paired with an electric discharge source, we investigated products resulting from the naphthalene discharge. Quantum chemical calculations were used to help assign species and investigate potential reaction pathways relevant to the interstellar medium. These products were searched for in TMC-1 using the QUIJOTE line survey, covering 31.0-50.3 GHz.Results. We confirm the detection of ethynylbenzene in TMC-1, and we also present a new molecular species, 1,2-diethynylbenzene, which could play an important role in the formation of naphthalene. Over ten products have been identified as resulting from the discharge, with only one of these species found in a previous IR-UV discharge study of naphthalene.Conclusions. Ethynylbenzene has definitively been detected in TMC-1, and while we have identified a potentially important species for the formation of naphthalene and an exothermic reaction pathway, there is no current indication of its presence in TMC-1.
The extremely sharp transition between molecular and ionized gas in the Horsehead nebula
Authors: Hernandez-Vera, C.; Guzman, V. V.; Goicoechea, J. R.; Maillard, V.; Pety, J.; Le Petit, F.; Gerin, M.; Bron, E.; Roueff, E.; Abergel, A.; Schirmer, T.; Carpenter, J.; Gratier, P.; Gordon, K.; Misselt, K.
Journal: ASTRONOMY & ASTROPHYSICS
Publication date: 2023/09/22
DOI: 10.1051/0004-6361/202347206
Abstract: Massive stars can determine the evolution of molecular clouds by eroding and photo-evaporating their surfaces with strong ultraviolet (UV) radiation fields. Moreover, UV radiation is relevant in setting the thermal gas pressure in star-forming clouds, whose influence can extend across various spatial scales, from the rims of molecular clouds to entire star-forming galaxies. Probing the fundamental structure of nearby molecular clouds is therefore crucial to understand how massive stars shape their surrounding medium and how fast molecular clouds are destroyed, specifically at their UV-illuminated edges, where models predict an intermediate zone of neutral atomic gas between the molecular cloud and the surrounding ionized gas whose size is directly related to the exposed physical conditions. We present the highest angular resolution (similar to 0 ”.5, corresponding to 207 au) and velocity-resolved images of the molecular gas emission in the Horsehead nebula, using CO J = 3-2 and HCO+ J = 4-3 observations with the Atacama Large Millimeter/submillimeter Array (ALMA). We find that CO and HCO+ are present at the edge of the cloud, very close to the ionization (H+/H) and dissociation fronts (H/H-2), suggesting a very thin layer of neutral atomic gas (<650 au) and a small amount of CO-dark gas (AV = 0.006-0.26 mag) for stellar UV illumination conditions typical of molecular clouds in the Milky Way. The new ALMA observations reveal a web of molecular gas filaments with an estimated thermal gas pressure of P-th = (2.3 - 4.0) x 10(6) K cm(-3), and the presence of a steep density gradient at the cloud edge that can be well explained by stationary isobaric photo-dissociation region (PDR) models with pressures consistent with our estimations. However, in the HII region and PDR interface, we find P-th,P-PDR > P-th,P-HII, suggesting the gas is slightly compressed. Therefore, dynamical effects cannot be completely ruled out and even higher angular observations will be needed to unveil their role.
Deep learning denoising by dimension reduction: Application to the ORION-B line cubes
Authors: Einig, Lucas; Pety, Jerome; Roueff, Antoine; Vandame, Paul; Chanussot, Jocelyn; Gerin, Maryvonne; Orkisz, Jan H.; Palud, Pierre; Santa-Maria, Miriam G.; Magalhaes, Victor de Souza; Beslic, Ivana; Bardeau, Sebastien; Bron, Emeric; Chainais, Pierre; Goicoechea, Javier R.; Gratier, Pierre; Guzman, Viviana V.; Hughes, Annie; Kainulainen, Jouni; Languignon, David; Lallement, Rosine; Levrier, Francois; Lis, Dariusz C.; Liszt, Harvey S.; Le Bourlot, Jacques; Le Petit, Franck; Oberg, Karin; Peretto, Nicolas; Roueff, Evelyne; Sievers, Albrecht; Thouvenin, Pierre-Antoine; Tremblin, Pascal
Journal: ASTRONOMY & ASTROPHYSICS
Publication date: 2023/09/21
DOI: 10.1051/0004-6361/202346064
Abstract: Context. The availability of large bandwidth receivers for millimeter radio telescopes allows for the acquisition of position-position-frequency data cubes over a wide field of view and a broad frequency coverage. These cubes contain a lot of information on the physical, chemical, and kinematical properties of the emitting gas. However, their large size coupled with an inhomogenous signal-to-noise ratio (S/N) are major challenges for consistent analysis and interpretation.Aims. We searched for a denoising method of the low S/N regions of the studied data cubes that would allow the low S/N emission to be recovered without distorting the signals with a high S/N.Methods. We performed an in-depth data analysis of the (CO)-C-13 and (CO)-O-17 (1-0) data cubes obtained as part of the ORION-B large program performed at the IRAM 30 m telescope. We analyzed the statistical properties of the noise and the evolution of the correlation of the signal in a given frequency channel with that of the adjacent channels. This has allowed us to propose significant improvements of typical autoassociative neural networks, often used to denoise hyperspectral Earth remote sensing data. Applying this method to the( 13)CO (1-0) cube, we were able to compare the denoised data with those derived with the multiple Gaussian fitting algorithm ROHSA, considered as the state-of-the-art procedure for data line cubes.Results. The nature of astronomical spectral data cubes is distinct from that of the hyperspectral data usually studied in the Earth remote sensing literature because the observed intensities become statistically independent beyond a short channel separation. This lack of redundancy in data has led us to adapt the method, notably by taking into account the sparsity of the signal along the spectral axis. The application of the proposed algorithm leads to an increase in the S/N in voxels with a weak signal, while preserving the spectral shape of the data in high S/N voxels.Conclusions. The proposed algorithm that combines a detailed analysis of the noise statistics with an innovative autoencoder architecture is a promising path to denoise radio-astronomy line data cubes. In the future, exploring whether a better use of the spatial correlations of the noise may further improve the denoising performances seems to be a promising avenue. In addition, dealing with the multiplicative noise associated with the calibration uncertainty at high S/N would also be beneficial for such large data cubes.
Searches for bridged bicyclic molecules in space-norbornadiene and its cyano derivatives
Authors: Martin-Drumel, Marie-Aline; Spaniol, Jean-Thibaut; Holzel, Helen; Agundez, Marcelino; Cernicharo, Jose; Moth-Poulsen, Kasper; Jacovella, Ugo
Journal: FARADAY DISCUSSIONS
Publication date: 2023/09/20
DOI: 10.1039/d3fd00016h
Abstract: The norbornadiene (NBD) molecule, C7H8, owes its fame to its remarkable photoswitching properties that are promising for molecular solar-thermal energy storage systems. Besides this photochemical interest, NBD is a rather unreactive species within astrophysical conditions and it should exhibit high photostability, properties that might also position this molecule as an important constituent of the interstellar medium (ISM)-especially in environments that are well shielded from short-wavelength radiation, such as dense molecular clouds. It is thus conceivable that, once formed, NBD can survive in dense molecular clouds and act as a carbon sink. Following the recent interstellar detections of large hydrocarbons, including several cyano-containing ones, in the dense molecular cloud TMC-1, it is thus logical to consider searching for NBD-which presents a shallow but non-zero permanent electric dipole moment (0.06 D)-as well as for its mono- and dicyano-substituted compounds, referred to as CN-NBD and DCN-NBD, respectively. The pure rotational spectra of NBD, CN-NBD, and DCN-NBD have been measured at 300 K in the 75-110 GHz range using a chirped-pulse Fourier-transform millimetre-wave spectrometer. Of the three species, only NBD was previously studied at high resolution in the microwave domain. From the present measurements, the derived spectroscopic constants enable prediction of the spectra of all three species at various rotational temperatures (up to 300 K) in the spectral range mapped at high resolution by current radio observatories. Unsuccessful searches for these molecules were conducted toward TMC-1 using the QUIJOTE survey, carried out at the Yebes telescope, allowing derivation of the upper limits to the column densities of 1.6 x 10(14) cm(-2), 4.9 x 10(10) cm(-2), and 2.9 x 10(10) cm(-2) for NBD, CN-NBD, and DCN-NBD, respectively. Using CN-NBD and cyano-indene as proxies for the corresponding bare hydrocarbons, this indicates that-if present in TMC-1-NBD would be at least four times less abundant than indene.
Hardware-Efficient Entangled Measurements for Variational Quantum Algorithms
Authors: Escudero, Francisco; Fernandez-Fernandez, David; Jauma, Gabriel; Penas, Guillermo F.; Pereira, Luciano
Journal: PHYSICAL REVIEW APPLIED
Publication date: 2023/09/20
DOI: 10.1103/PhysRevApplied.20.034044
Abstract: Variational algorithms have received significant attention in recent years due to their potential to solve practical problems using noisy intermediate-scale quantum (NISQ) devices. A fundamental step of these algorithms is the evaluation of the expected value of Hamiltonians, and hence efficient schemes to perform this task are required. The standard approach employs local measurements of Pauli operators and requires a large number of circuits. An alternative is to use entangled measurements, which might introduce additional gates between physically disconnected qubits that harm the performance. To solve this problem, we propose hardware-efficient entangled measurements (HEEMs), that is, measurements that permit only entanglement between physically connected qubits. We show that this strategy enhances the evaluation of molecular Hamiltonians in NISQ devices by reducing the required circuits without increasing their depth. We provide quantitative metrics of how this approach offers better results than local measurements and arbitrarily entangled measurements. We estimate the ground-state energy of the H2O molecule with classical simulators and quantum hardware using the variational quantum eigensolver with HEEM.
Trihydrogen Cation Helium Clusters: A New Potential Energy Surface
Authors: Breton, Jose; Hernandez-Rojas, Javier; Hernandez, Marta I.; Campos-Martinez, Jose; Gonzalez-Lezana, Tomas
Journal: CHEMPHYSCHEM
Publication date: 2023/09/19
Abstract: We present a new analytical potential energy surface (PES) for the interaction between the trihydrogen cation and a He atom, H3+-He ${{H}_{3}<^>{+}-He}$, in its electronic ground state. The proposed PES has been built as a sum of two contributions: a polarization energy term due to the electric field generated by the molecular cation at the position of the polarizable He atom, and an exchange-repulsion and dispersion interactions represented by a sum of atom-bond potentials between the three bonds of H3+ ${{H}_{3}<^>{+}}$ and the He atom. All parameters of this new PES have been chosen and fitted from data obtained from high-level ab-initio calculations. Using this new PES plus the Aziz-Slaman potential for the interaction between Helium atoms and assuming pair-wise interactions, we carry out classical Basin-Hopping global optimization, semiclassical BH with Zero Point Energy corrections, and quantum Diffusion Monte Carlo simulations. We have found the minimum energy configurations of small He clusters doped with H3+ ${{H}_{3}<^>{+}}$, H3+HeN ${{H}_{3}<^>{+}{left(Heright)}_{N}}$, with N=1-16. The study of the energies of these clusters allows us to find a pronounced anomaly for N=12, in perfect agreement with previous experimental findings, which we relate to a greater relative stability of this aggregate. A simple and new analytical potential energy surface (PES) for the interaction between the rigid trihydrogen cation and the helium atom is presented. This analytical PES is based on polarization and dispersion-repulsion forces. The parameters of this PES are fitted from data obtained from post Hartree-Fock calculations at the CCSD(T) level.image