Prediction of the neutron drip line in oxygen isotopes using quantum computation

TL;DR

This paper demonstrates using variational quantum eigensolvers on quantum hardware to predict the neutron drip line in oxygen isotopes, achieving near-exact energies and identifying $^{24}$O as the drip line nucleus.

Contribution

It introduces a quantum computing approach with circuit optimization and error mitigation to accurately determine nuclear drip lines, a novel application in nuclear physics.

Findings

Reproduced ground state energies within a few percent error on quantum hardware.

Identified $^{24}$O as the neutron drip line nucleus in oxygen isotopes.

Showed feasibility of quantum algorithms for complex nuclear structure problems.

Abstract

In the noisy intermediate-scale quantum era, variational algorithms have become a standard approach to solving quantum many-body problems. Here, we present variational quantum eigensolver (VQE) results of selected oxygen isotopes within the shell model description. The aim of the present work is to locate the neutron drip line of the oxygen chain using unitary coupled cluster (UCC) type ansatze with different microscopic interactions (DJ16, JISP16, and N3LO), in addition to a phenomenological USDB interaction. While initially infeasible to execute on contemporary quantum hardware, the size of the problem is reduced significantly using qubit tapering techniques in conjunction with custom circuit design and optimization. The optimal values of ansatz parameters from classical simulation are taken for the DJ16 interaction, and the tapered circuits are run on IonQ's Aria, a trapped-ion quantum computer. After applying gate error mitigation for three isotopes, we reproduced exact ground state energies within a few percent error. The post-processed results from hardware also clearly show $^{24}$O as the drip line nucleus of the oxygen chain. Future improvements in quantum hardware could make it possible to locate drip lines of heavier nuclei.