Members:

• Luigi Coraggio
• Nunzio Itaco
• Giovanni De Gregorio

Keywords:

• Nuclear shell model
• Effective interactions
• Nuclear spectroscopy

• Collective models
• b decay and electron-capture rates
• Neutrinoless double-b decay
• Quantum computing

Research Profile:

• Nuclear structure calculations with realistic potentials

The Nuclear Theory group at the Department of Mathematics and Physics of University of Campania “Luigi Vanvitelli” has a long-standing experience in nuclear structure calculations performed starting from realistic potentials. More precisely, during last years we have worked extensively on the problem of the derivation of effective shell-model Hamiltonians and decay operators from realistic potentials by way of many-body perturbation theory, and on their assessment for nuclear structure calculations.

Recently, our interest has been focused on two main aspects which are strictly connected to these themes:

• derivation of the effective shell-model Hamiltonian and from chiral potentials including three body terms;
• derivation of effective shell-model decay operators to investigate the well-known problem of the ``quenching’’ of the axial coupling constant for nuclear structure calculations of the beta decay.

• Neutrino physics

The search of neutrinoless double-beta (0nbb) decay is pursued in many laboratories all around the world to improve our knowledge of the properties of neutrinos and shed light on the limitations of the Standard Model. The rate of this decay is ruled by both the unknown neutrino effective mass and the nuclear matrix elements M0n associated with the 0nbb transition. M0n cannot be measured, hence the success of the experimental programs depends on their accurate theoretical prediction. Currently, different nuclear-structure models provide M0n  differing up to a factor three, thus affecting the estimation of the needed detector sensitivity.

During last years, our group has pursued a microscopic framework to the calculation of M0n within the realistic shell-model, namely deriving effective shell-model Hamiltonians and b-decay operators from realistic nuclear forces. To validate our approach, we have first calculated nuclear matrix elements M2n of the two-neutrino double-beta (2nbb) decay for nuclei of current interest for experimental collaborations – 48Ca, 76Ge, 82Se, 100Mo, 130Te, and 136Xe - to test the reliability of our predicted wave functions, then also M0n  have been calculated for the same nuclei.

In a near future, we are going to approach this subject by employing two-body meson-exchange currents that can be derived within the chiral perturbation theory consistently with the starting nuclear Hamiltonian. 

• Large-scale shell model and support to experimental collaborations

Our group has performed many large-scale shell-model calculations for a large sample of medium- and heavy-mass nuclei. The aim of these studies is to investigate exotic nuclear-structure features that could be reproduced only accounting for large model spaces and many-valence nucleons systems. This has been achieved also introducing novel approaches to the truncation of model space by way of unitary transformations. All these items which have been above presented have a strong correlation with past, present and future experiments performed at various international laboratories. 

• Equation of Motion Phonon Method

During the last years members of our group have developed the many-body method named Equation of Motion Phonon Method (EMPM). This method has allowed to study several properties of nuclei, such as low-energy spectroscopy, giant resonances, bulk properties of atomic nuclei. In the near future we plan to extend the method in order to tackle a wider range of nuclei and in particular to develop the formalism for 2-particles (holes) as well as a L-hyperon external to a doubly magic core. Moreover, the implementation of the Singular Value Decomposition method within the EMPM to eliminate exactly the center-of-mass spurious motion is in progress. 

• Quantum computing and machine learning for nuclear physics

Quantum computing represents a radical change in computational paradigms. Quantum computers and simulators have revolutionary potential in many areas, from the optimization of production processes to the solution of complex problems in several fields, like chemistry, biology, material science and fundamental Physics. The recent demonstration of the possibility to realize the quantum supremacy - namely the ability of a quantum computer to perform a task that is impossible for a classical computer - shows the possibility of making the quantum ecosystem a real productive tool already in the next decade. 

To achieve such a challenging scope, a huge effort is needed to develop quantum technologies that are necessary to realize noise-resistant quantum process units (QPUs) and noise-resilient algorithms. 

Our plan is to pave the way towards the diagonalization of the Hamiltonian of a nuclear system on a quantum computer. Starting from a given configuration space we plan to map the nuclear Hamiltonian defined in such a space on a quantum computer. After this mapping we have to solve the eigenvalue problem for ground and excited states by resorting to numerical methods developed on purpose for quantum devices. In particular, we plan to use the variational quantum eigensolver (VQE) to determine the ground state of the nuclear system, and then the quantum equation of motion approach (qEOM) – that is an extension of the VQE - to calculate its excited states. These calculations will be performed both simulating a quantum device and running test calculation on a real quantum machine publicly available like the IBM ones. 

Current research projects:

1. PON Ricerca e Innovazione 2014-2020

2. INFN Research Network MoNStRe

3. Bando di Ateneo per il finanziamento di progetti di ricerca fondamentale ed applicata dedicato ai giovani Ricercatori: Progetto TQC (Technologies for Quantum Computing)

Recent publications:

1. Shell-model calculation of 100Mo double-b decay, L. Coraggio, N. Itaco, G. De Gregorio, A. Gargano, R. Mancino, and F. Nowacki, Phys. Rev. C 105, 034312 (2022).

2. Spectroscopic properties of 4He within a multiphonon approach, G. De Gregorio, F. Knapp, N. Lo Iudice, and P. Vesely, Phys. Rev. C 105, 024326 (2022).

3. Shell-model study of titanium isotopic chain with chiral two- and three-body forces, L. Coraggio, G. De Gregorio, A. Gargano, N. Itaco, T. Fukui, Y. Z. Ma, and F. R. Xu, Phys. Rev. C 104, 054304 (2021).

4. Removal of the center of mass in nuclei and its effects on 4He, G. De Gregorio, F. Knapp, N. Lo Iudice, and P. Vesely, Phys. Lett. B 821, 136636 (2021).

5. Shell-model study of calcium isotopes toward their drip line, L. Coraggio, G. De Gregorio, A. Gargano, N. Itaco, T. Fukui, Y. Z. Ma, and F. R. Xu, Phys. Rev. C 102, 053326 (2020).

6. Perturbative Approach to Effective Shell-Model Hamiltonian and Operators, L. Coraggio and N. Itaco, Frontiers in Physics 8, 345 (2020).

7. Continuum and three-nucleon force in Borromean system: The 17Ne case, Y. Z. Ma, F. R. Xu, N. Michel, S. Zhang, J. G. Li, B. S. Hu, L. Coraggio, N. Itaco, and A. Gargano, Phys. Lett. B 808, 135673 (2020).

8. Calculation of the neutrinoless double-beta decay matrix element within the realistic shell model, L. Coraggio, A. Gargano, N. Itaco, R. Mancino, and F. Nowacki, Phys. Rev. C 101, 044315 (2020).

9. Chiral three-nucleon force and continuum for dripline nuclei and beyond, Y. Z. Ma, F. R. Xu, L. Coraggio, B. S. Hu, J. G. Li, T. Fukui, L. De Angelis, N. Itaco, and A. Gargano, Phys. Lett. B 802, 135257 (2020).

10. Proper treatment of the Pauli principle in mirror nuclei within the microscopic particle(hole)-phonon scheme, G. De Gregorio, F. Knapp, N. Lo Iudice, and P. Vesely, Phys. Rev. C 101, 024308 (2020).

11. Contribution of chiral three-body forces to the monopole component of the effective shell-model Hamiltonian, Y. Z. Ma, L. Coraggio, L. De Angelis, T. Fukui, A. Gargano, N. Itaco, and F. R. Xu, Phys. Rev. C 100, 034324 (2019).

12. Renormalization of the Gamow-Teller operator within the realistic shell model, L. Coraggio, L. De Angelis, T. Fukui, A. Gargano, N. Itaco, and F. Nowacki, Phys. Rev. C 100, 014316 (2019).

13. Microscopic multiphonon approach to nuclei with a valence hole in the oxygen region, G. De Gregorio, F. Knapp, N. Lo Iudice, and P. Vesely, Phys. Rev. C 99, 014316 (2019).

14. Realistic shell-model calculations for p-shell nuclei including contributions of a chiral three-body force, T. Fukui, L. De Angelis, Y. Z. Ma, L. Coraggio, A. Gargano, N. Itaco, and F. R. Xu, Phys. Rev. C 98, 044305 (2018).

15. Microscopic multiphonon approach to spectroscopy in the neutron-rich oxygen region, G. De Gregorio, F. Knapp, N. Lo Iudice, and P. Vesely, Phys. Rev. C 97, 034311 (2018).