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1.
Front Chem ; 7: 662, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31632953

RESUMO

Quantum bits (qubits) constitute the most elementary building-blocks of any quantum technology, where information is stored and processed in the form of quantum superpositions between discrete energy levels. In particular, the fabrication of quantum processors is a key long-term goal that will allow us conducting specific tasks much more efficiently than the most powerful classical computers can do. Motivated by recent experiments in which three addressable spin qubits are defined on a potential single-molecule quantum processor, namely the [Gd(H2O)P5W30O110]12- polyoxometalate, we investigate the decohering effect of magnetic noise on the encoded quantum information. Our state-of-the-art model, which provides more accurate results than previous estimates, show a noticeable contribution of magnetic noise in limiting the survival timescale of the qubits. Yet, our results suggest that it might not be the only dephasing mechanism at play but other mechanisms, such as lattice vibrations and physical movement of magnetic nuclei, must be considered to understand the whole decoherence process.

2.
Inorg Chem ; 58(18): 11883-11892, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31490061

RESUMO

Molecular nanomagnets based on mononuclear metal complexes, also known as single-ion magnets (SIMs), are crossing challenging boundaries in molecular magnetism. From an experimental point of view, this class of magnetic molecules has expanded from lanthanoid complexes to both d-transition metal and actinoid complexes. From a theoretical point of view, more and more improved models have been developed, and we are now able not only to calculate the electronic structure of these systems on the basis of their molecular structures but also to unveil the role of vibrations in the magnetic relaxation processes, at least for lanthanoid and d-transition metal SIMs. This knowledge has allowed us to optimize the behavior of dysprosocenium-based SIMs until reaching magnetic hysteresis above liquid-nitrogen temperature. In this contribution, we offer a brief perspective of the progress of theoretical modeling in this field. We start by reviewing the developed methodologies to investigate the electronic structures of these systems and then move on focus to the open problem of understanding and optimizing the vibrationally induced spin relaxation, especially in uranium-based molecular nanomagnets. Finally, we discuss the differences in the design strategies for 4f and 5f SIMs, including an analysis of the metallocenium family.

3.
J Phys Chem Lett ; 9(16): 4522-4526, 2018 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-30044106

RESUMO

The pursuit of novel functional building blocks for the emerging field of quantum computing is one of the most appealing topics in the context of quantum technologies. Herein we showcase the urgency of introducing peptides as versatile platforms for quantum computing. In particular, we focus on lanthanide-binding tags, originally developed for the study of protein structure. We use pulsed electronic paramagnetic resonance to demonstrate quantum coherent oscillations in both neodymium and gadolinium peptidic qubits. Calculations based on density functional theory followed by a ligand field analysis indicate the possibility of influencing the nature of the spin qubit states by means of controlled changes in the peptidic sequence. We conclude with an overview of the challenges and opportunities opened by this interdisciplinary field.


Assuntos
Metaloproteínas/química , Peptídeos/química , Teoria Quântica , Cátions/química , Espectroscopia de Ressonância de Spin Eletrônica , Elementos da Série dos Lantanídeos/química , Modelos Químicos
4.
Chem Sci ; 9(13): 3265-3275, 2018 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-29780458

RESUMO

Very recently the closely related fields of molecular spin qubits, single ion magnets and single atom magnets have been shaken by unexpected results. We have witnessed a jump in the phase memory times of spin qubits from a few microseconds to almost a millisecond in a vanadium complex, magnetic hysteresis up to 60 K in a dysprosium-based magnetic molecule and magnetic memory up to 30 K in a holmium atom deposited on a surface. With single-molecule magnets being more than two decades old, this rapid improvement in the physical properties is surprising and its explanation deserves urgent attention. The general assumption of focusing uniquely on the energy barrier is clearly insufficient to model magnetic relaxation. Other factors, such as vibrations that couple to spin states, need to be taken into account. In fact, this coupling is currently recognised to be the key factor that accounts for the slow relaxation of magnetisation at higher temperatures. Herein we will present a critical perspective of the recent advances in molecular nanomagnetism towards the goal of integrating spin-phonon interactions into the current computational methodologies of spin relaxation. This presentation will be placed in the context of the well-known models developed in solid state physics, which, as we will explain, are severely limited for molecular systems.

5.
J Comput Chem ; 37(13): 1238-44, 2016 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-26833799

RESUMO

SIMPRE is a fortran77 code which uses an effective electrostatic model of point charges to predict the magnetic behavior of rare-earth-based mononuclear complexes. In this article, we present SIMPRE1.2, which now takes into account two further phenomena. First, SIMPRE now considers the hyperfine and quadrupolar interactions within the rare-earth ion, resulting in a more complete and realistic set of energy levels and wave functions. Second, and to widen SIMPRE's predictive capabilities regarding potential molecular spin qubits, it now includes a routine that calculates an upper-bound estimate of the decoherence time considering only the dipolar coupling between the electron spin and the surrounding nuclear spin bath. Additionally, SIMPRE now allows the user to introduce the crystal field parameters manually. Thus, we are able to demonstrate the new features using as examples (i) a Gd-based mononuclear complex known for its properties both as a single ion magnet and as a coherent qubit and (ii) an Er-based mononuclear complex. © 2016 Wiley Periodicals, Inc.

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