Session H06: Many Body Quantum Computations in Nuclear Physics

Nuclear structure and reactions from ab initio calculations

An overarching goal of nuclear physics is to arrive at the comprehensive understanding – in terms of the laws of quantum mechanics and the underlying theory of the strong force (quantum chromodynamics) – of atomic nuclei and their interactions, and to use this understanding to accurately predict nuclear properties that are difficult to measure or simply inaccessible to experiment, but play a fundamental role in explaining the inner workings of the Universe or are critical to the national security. I will present first-principles calculations of nuclear structural and reaction properties to reveal the imprints of the strong nuclear force in rare isotopes with large proton-neutron asymmetry located at the edges of nuclear stability (the drip-lines) and to predict thermonuclear reaction rates of interest for stellar nucleosynthesis and fusion energy technology.   

Coupled-cluster calculations of atomic nuclei

The past few decades have seen remarkable progress in our ability to describe atomic nuclei from first principle. It was only a few years ago that the lightest oxygen isotopes defined the absolute limits of our capabilities. Today, we set those limits in the tin isotopes and have already set our sights on heavier nuclei like lead and those beyond. Although a part of the reason for these advances lie in the ever-increasing capacity of high performance computing systems, we owe most of our progress to the introduction of many-body methods that scale polynomially with the number of particles in the system and to new interaction models that are based on the symmetries of quantum chromodynamics (QCD), the quantum field theory of the strong nuclear force. In this talk I will present some of our latest results in medium-mass nuclei obtained within the coupled-cluster framework. This framework consists of a series of methods to calculate properties of many-body systems to various degrees of precision. I will discuss a study of the charge, neutron and weak size of neutron-rich calcium isotopes and the structure of nickel-78, a doubly-magic closed-shell isotope of nickel that has an extreme neutron-to-proton ratio with 28 protons and 50 neutrons. The highlight will be a solution to the quenching puzzle of beta decays, a long-standing problem in nuclear physics where the observed beta-decay rates of nuclei are systematically smaller than theoretical predictions. All of these calculations has been performed using two- and three-body interactions obtained from chiral effective field theory, an interaction model of the nuclear force based on the symmetries of QCD.   

Nuclear structure and quantum phase transitions with lattice effective field theory

How do protons and neutrons bind to form nuclei? While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. I discuss recent work using lattice simulations which shows nature is near a quantum phase transition between a nuclear liquid and Bose condensate of alpha particles. I also summarize some new developments and work in progress in lattice effective field theory.