Reduced Entanglement Requirements in Fermionic Simulation Through Fermion-To-Qubit Mapping Optimization

Màster Oficial de Ciència i Tecnologia Quàntiques / Quantum Science and Technology, Facultat de Física, Universitat de Barcelona. Curs: 2022-2023. Tutors: Antonio Acín, Leonardo ZambranoIn ab-initio electronic structure simulations, fermion-to-qubit mappings represent the initial encoding step of the fermionic problem into qubits. This work introduces a novel method for deriving optimized mappings that significantly reduce the entanglement requirements for prepared states of interest. The presence of single and double electronic excitations drives the optimization of the mapping, greatly simplifying correlations for target states in the qubit space. Additionally, the code implementation for designing arbitrary ternary tree mappings in the Tequila Python library is provided. Enhanced simulation accuracy is validated on the optimized mappings both in quantum computing, using the variational quantum eigensolver, and in tensor networks by employing density matrix renormalization group on a matrix product state

Chiral recognition by dissolution dynamic nuclear polarization NMR spectroscopy

The recognition of enantiomeric molecules by chemical analytical techniques is still a challenge. A method based on d-DNP (dissolution dynamic nuclear polarization) NMR spectroscopy to study chiral recognition was described for the first time [1]. DNP allows NMR sensitivity to be boosted by several orders of magnitude, overcoming one of the main limitations of NMR spectroscopy [2]. A method integrating d-DNP and 13C-NMR-aided enantiodifferentiation using chiral solvating agents (CSA) was developed, in which only the chiral analyte was hyperpolarized and selectively observed by NMR. The described method enhances the sensitivity of the conventional NMR-based procedure [3] and lightens the common problem of signal overlapping between analyte and CSA. As proof of concept, racemic metabolite 13C-labeled DL-methionine was enantiodifferentiated by a single-scan 13C-NMR experiment. This method entails a step forward in the chiral recognition of small molecules by NMR spectroscopy; it opens new possibilities in situations where the sensitivity is limited, for example, when low analyte concentration is available or when measurement of an insensitive nucleus is required. The advantages and current limitations of the method, as well as future perspectives, are discussed

Synthesis of (±)-Serralongamine A and the Revised Structure of Huperzine N

A revised structure for the Lycopodium alkaloid huperzine N is proposed and confirmed by synthesis. The key synthetic steps involve an epimerization of a cis-5-oxodecahydroquinoline to the corresponding trans isomer and a coupling, followed by a diastereoselective hydrogenation using Wilkinson's catalyst to incorporate the pyridylmethyl moiety. This route allowed the alkaloid serralongamine A to be synthesized for the first time, and two additional steps led to the revised structure of huperzine N, both products bearing an unusual decahydroquinoline stereostructure

Ile-Phe Dipeptide Self-Assembly: Clues to Amyloid Formation

AbstractPeptidic self-assembled nanostructures are said to have a wide range of applications in nanotechnology, yet the mechanistic details of hierarchical self-assembly are still poorly understood. The Phe-Phe recognition motif of the Alzheimer’s Aβ peptide is the smallest peptide able to assemble into higher-order structures. Here, we show that the Ile-Phe dipeptide analog is also able to self-associate in aqueous solution as a transparent, thermoreversible gel formed by a network of fibrillar nanostructures that exhibit strong birefringence upon Congo red binding. Besides, a second dipeptide Val-Phe, differing only in a methyl group from the former, is unable to self-assemble. The detailed analysis of the differential polymeric behavior of these closely related molecules provides insight into the forces triggering the first steps in self-assembly processes such as amyloid formation

Hyperpolarization-Enhanced NMR Spectroscopy of Unaltered Biofluids Using Photo-CIDNP

Altres ajuts: acords transformatius de la UABThe direct and unambiguous detection and identification of individual metabolite molecules present in complex biological mixtures constitute a major challenge in (bio)analytical research. In this context, nuclear magnetic resonance (NMR) spectroscopy has proven to be particularly powerful owing to its ability to provide both qualitative and quantitative atomic-level information on multiple analytes simultaneously in a noninvasive manner. Nevertheless, NMR suffers from a low inherent sensitivity and, moreover, lacks selectivity regarding the number of individual analytes to be studied in a mixture of a myriad of structurally and chemically very different molecules, e.g., metabolites in a biofluid. Here, we describe a method that circumvents these shortcomings via performing selective, photochemically induced dynamic nuclear polarization (photo-CIDNP) enhanced NMR spectroscopy on unmodified complex biological mixtures, i.e., human urine and serum, which yields a single, background-free one-dimensional NMR spectrum. In doing this, we demonstrate that photo-CIDNP experiments on unmodified complex mixtures of biological origin are feasible, can be performed straightforwardly in the native aqueous medium at physiological metabolite concentrations, and act as a spectral filter, facilitating the analysis of NMR spectra of complex biofluids. Due to its noninvasive nature, the method is fully compatible with state-of-the-art metabolomic protocols providing direct spectroscopic information on a small, carefully selected subset of clinically relevant metabolites. We anticipate that this approach, which, in addition, can be combined with existing high-throughput/high-sensitivity NMR methodology, holds great promise for further in-depth studies and development for use in metabolomics and many other areas of analytical research

Reducing entanglement with physically inspired fermion-to-qubit mappings

In ab initio electronic structure simulations, fermion-to-qubit mappings represent the initial encoding step from the problem of fermions into a problem of qubits. This work introduces a physically inspired method for constructing mappings that significantly simplify entanglement requirements when one is simulating states of interest. The presence of electronic excitations drives the construction of our mappings, reducing correlations for target states in the qubit space. To benchmark our method, we simulate ground-states of small molecules and observe an enhanced performance when compared with classical and quantum variational approaches from prior research using conventional mappings. In particular, on the quantum side, our mappings require a reduced number of entangling layers to achieve accuracy for LiH, H2, (H2)2, H≠4 stretching, and benzene’s π system using the RY hardware-efficient ansatz. In addition, our mappings also provide an enhanced ground-state simulation performance in the density matrix renormalization group algorithm for the N2 molecule

Optimized polarization build-up times in dissolution DNP-NMR using a benzyl amino derivative of BDPA

The synthesis of two novel BDPA-like radicals, a benzyl amino (BAm-BDPA, 7) and a cyano (CN-BDPA, 5) derivative, is reported and their behaviour as polarizing agents for fast dissolution Dynamic Nuclear Polarization (DNP) is evaluated. The radical 7 is a promising candidate for DNP studies since it is soluble in neat [1-13C]pyruvic acid (PA), and therefore the use of an additional glassing agent for sample homogeneity is avoided. In addition, a 60 mM sample of 7 offers optimum 13C NMR signal enhancements using fairly short polarization times (about 1800 s). It is shown that DNP-NMR measurements using 7 can be performed much more efficiently in terms of the signal enhancement per polarization build-up time unit than when using the reference OX63 or BDPA radicals. These enhanced features are translated to a substantial reduction of polarization times that represents an optimum temporary use of the DNP polarizer and allow economized liquid helium consumption.This research was supported by the DGI Grants “POMAs” (CTQ2010-19501) and “Be-Well” (CTQ2013-40480 R), MINECO (CTQ2012-32436), AGAUR Grant (2014SGR-0017) and MINECO Grant (PTA 2011-5037-I) for the subprogram Personal T´ecnico de Apoyo. We also thank the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), the Consejo Superior de Investigaciones Cient´ıcas for the JAE Grant, and Amable Bernab´e for his work in MALDI spectrometry. NMR studies were carried out at the joint NMR facility of the Universitat Aut`onoma de Barcelona and CIBER-BBN (Cerdanyola del Vall`es).Peer reviewe

Redox-Active Metallacarborane-Decorated Octasilsesquioxanes. Electrochemical and Thermal Properties

Polyanionic and electroactive hybrids based on octasilsesquioxanes bearing metallacarborane units are developed. They show remarkable solubility in organic solvents and outstanding thermal stability. The metallacarboranes act as independent units simultaneously undergoing the reversible redox process.We acknowledge support by MINECO [Grants CTQ2013- 44670-R, CTQ2012-32436, and CTQ2015-64436-P and the “Severo Ochoa” Program for Centers of Excellence in R&D (SEV-2015-0496)] and Generalitat de Catalunya (Grant 2014/ SGR/149). J.C.-G. thanks to the CSIC for an intramural grant. V.S.-A. thanks MICINN (Grant CTQ2010-16237) for the FPI grant.Peer reviewe

pH-triggered removal of nitrogenous organic micropollutants from water by using metal-organic polyhedra

Altres ajuts: this work funded by the CERCA Programme/Generalitat de Catalunya and through a fellowship (LCF/BQ/PR20/11770011) from the "la Caixa" Foundation (ID 100010434). L.H.L. acknowledges the support from the Spanish State Research Agency (PRE2019-088056).Water pollution threatens human and environmental health worldwide. Thus, there is a pressing need for new approaches to water purification. Herein, we report a novel supramolecular strategy based on the use of a metal-organic polyhedron (MOP) as a capture agent to remove nitrogenous organic micropollutants from water, even at very low concentrations (ppm), based exclusively on coordination chemistry at the external surface of the MOP. Specifically, we exploit the exohedral coordination positions of Rh-MOP to coordinatively sequester pollutants bearing N-donor atoms in aqueous solution, and then harness their exposed surface carboxyl groups to control their aqueous solubility through acid/base reactions. We validated this approach for removal of benzotriazole, benzothiazole, isoquinoline, and 1-napthylamine from water

An Enantiopure Propeller‐Like Trityl‐Brominated Radical: Bringing Together a High Racemization Barrier and an Efficient Circularly Polarized Luminescent Magnetic Emitter

A new persistent organic free radical has been synthetized with Br atoms occupying the ortho‐ and para‐positions of a trityl core. After the isolation of its two propeller‐like atropisomers, Plus (P) and minus (M), their absolute configurations were assigned by a combination of theoretical and experimental data. Remarkably, no hints of racemization were observed up to 60 °C for more than two hours, due to the higher steric hindrance imposed by the bulky Br atoms. Therefore, when compared to its chlorinated homologue (t1/2=18 s at 60 °C), an outstanding stability against racemization was achieved. A circularly polarized luminescence (CPL) response of both enantiomers was detected. This free radical shows a satisfactory luminescent dissymmetry factor (|glum(592 nm)|≈0.7×10−3) despite its pure organic nature and low luminescence quantum yield (LQY). Improved organic magnetic CPL emitters derived from the reported structure can be envisaged thanks to the wide possibilities that Br atoms at para‐positions offer for further functionalization.The authors are grateful for the financial support received from: MOTHER project (MAT2016-80826-R) granted by the DGI (Spain), GenCat (2017-SGR-918) financed by DGR (Catalunya) and the Spanish Ministry of Economy and Competitiveness (PGC2018-095808-B-I00 and PGC2018-101181-B-I00 projects) and through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496) and through the “Proyecto Interdisciplinar de Frontera“, FIP-2018 HECTIC-PTM. We acknowledge the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (ERC-2015-STG-677023). This study has been also supported by the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. P. M. B. gratefully acknowledges financial support from the Juan de la Cierva-Formación 2015 programme (FJCI-2015-23577) supported by MINECO and, together with J.V, A. G. C. also thanks RyC-2013-12943 contract from MINECO. We also thankthe Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, for allocating instrument time to this project