Personale docente

Dr. Alessandro Chiesa got the Master Degree in Physics (2012) and PhD in Physics (2016) at the University of Parma. In 2017 he was Visiting Scientist at Jülich Forschungszentrum (Germany). In 2016, 2018 e 2019 he worked as post-DOC in the Molecolar Magnetism group at the University of Parma and from 2020 he is Research Associate at the Department of Mathematical, Physical and Computer Sciences of the University of Parma within the spin-based Quantum Science (SQS) group. 

His research activity is focused on the theoretical modeling of Molecular Spin systems. The target is twofold: on the one hand, the development of models to understand fundamental quantum mechanical phenomena (such as the CISS effect); on the other hand, the development of schemes exploiting Molecular Nanomagnets for future technological applications, in the field of Quantum Information Processing.

In this perspective, the research on the physical implementation of quantum computation had a multi-disciplinary character, with the aim of exploring different promising routes. In particular, I have investigated electronic and nuclear spin systems (controlled by electro-magnetic pulses), spin ensembles strongly coupled to photons in coplanar resonators, electro-mechanical resonators.

Current leading technologies are based on trapped ions or superconducting qubits. I have used the latter to design and run quantum computing experiments in collaboration with IBM. These chips have already reached an intermediate size, but are still subject to significant errors. The realization of a scalable device supporting quantum error correction is mandatory to implement complex algorithms but is still very demanding. Indeed, standard error correction codes use many physical qubits to encode a single protected logical qubit, yielding a large overhead of resources and making the control of such a platform very hard. Molecular Nanomagnets could represent the solution of this issue, as we have recently proposed: indeed, they provide many accessible levels (embedded in a single molecule) which could be exploited to implement error correction at the single-object level. This would make quantum error correction and operations much easier to achieve in the short term. Dr. chiesa has designed codes protecting the system form the most important error sources and schemes to implement them in a fault-tolerant manner, i.e. keeping errors controlled even during computation.

The close collaboration with other theoreticians (at the University of Pavia and Modena), chemists and experimental physicists (at the University of Manchester, Florence, Zaragoza, Barcelona) has allowed us to propose schemes for molecular qubits based on existing molecules and available experimental technologies, in order to design forthcoming proof-of-principle experiments. In this context, the SQS group has recently demonstrated the first proof-of-concept quantum simulator based on ¹⁷³Yb, manipulated by radio-frequency pulses. The molecules provides a qudit consisting of 6 nuclear spin levels coupled by a sizable hyperfine interaction to an electronic effective spin 1/2, which was used to simulate either the dynamics of a single multi-level object or of a multi-qubit systems.

Chirality-induced spin-selectivity (CISS) effect provides an important tool to overcome a crucial challenge for using  molecular spin in quantum information, namely their readout and high-temperature initialization. Indeed, their weak coupling with external fields makes it very hard to read their spin state at the single-molecule level. The SQS group has proposed a scheme to overcome this hurdle by linking the spin to a chiral molecule in an electron donor-chiral bridge-acceptor system, which exploits CISS effect in locking spin to charge even at room temperature and hence makes the tiny spin information more easily accessible. 

Going to the molecular level could also be the route to gain a deeper understanding of CISS. In particular, by removing complex metallic interfaces we can focus on the role of the chiral bridge alone in introducing a spin polarization. In collaboration with Freie Universitat Berlin, Univerity of Florence and Northwestern Univeristy, the SQS group has designed time-resolved electron paramagnetic resonance (TREPR) experiments to show the occurrence of CISS in molecular systems and we have contributed to unveil its first evidence in an experiment on molecules synthesized at the Northwestern University.

Further TREPR experiments, combined with first-principles calculations and minimal many-body models will help us in shedding light on the origin  of CISS in the near future.

To model the behavior of Molecular Nanomagnets, Dr. Chiesa uses advanced theoretical techniques, combined with the interpretation of experimental data. On the theoretical side, he contributed to develop (in collaboration with Prof. Pavarini, Jülich Forschunszentrum) a first-principle approach to build many-body models for Molecular Nanomagnets, starting from density functional theory self-consistent calculations and explicitly including strong electron-electron correlations, an essential ingredient to describe these systems.

On the experimental side, inelastic neutron scattering is the best choice to achieve an accurate description of low-energy excitations of Molecular Nanomagnets, possibly guided by first-principle calculations. Hence, he took part to the design, realization and interpretation of experiments at international facilities such as the Institute Laue Langevin in Grenoble or ISIS Neutron and Muon Source in UK. In particular, four-dimensional inelastic neutron scattering allows us probe the spatial structure of the molecular eigenstates, which constitute an unambiguous fingerprint of the magnetic Hamiltonian.

Finally, Dr. Chiesa has worked on the study of the relaxation dynamics of Molecular Nanomagnets, the starting point to realize high-density magnetic memories for information storage.

This research activity is witnessed by 53 papers on important international peer-reviewed journals (about 1500 citations, h-index 22), among which 1 Science, 1 Advanced Materials, 1 Nature Physics, 1 Nature Communications, 3 Physical Review Letters, 1 PRX Quantum, 3 Journal of American Chemical Society, 6 Chemical Science, 2 Angewandte Chemie Int. Ed., 1 Chem, 5 Journal of Physical Chemistry Letters. He is Referee of many journals, including Physical Review Letters, Physical Review X and Nature Communications and he regularly attends both national and international scientific conferences, also as an invited speaker.

In 2018 he was awarded the “European Award for Doctoral Thesis in Molecular Magnetism” and the “Galileo Galilei” award for young researchers by Rotary International (Distretto 2072) and in 2021 the "Advances in Magnetism Award", sponsored by AIP Advances, published by AIP Publishing. He got the National Academic Qualification as Associate Professor in Theoretical Physics of Matter (SC 02/B2) in 2020.