Variational approaches to constructing the many-body nuclear ground state for quantum computing

We explore the preparation of specific nuclear states on gate-based quantum hardware using variational algorithms. Large-scale classical diagonalizations of the nuclear shell model have reached sizes of 109???1010 basis states but are still severely limited by computational resources. Quantum computing can, in principle, solve such systems exactly with exponentially fewer resources than classical computing. Exact solutions for large systems require many qubits and large gate depth, but variational approaches can effectively limit the required gate depth. We use the unitary coupled cluster approach to construct approximations of the ground-state vectors, later to be used in dynamics calculations. The testing ground is the phenomenological shell model space, which allows us to mimic the complexity of the internucleon interactions. We find that often one needs to minimize over a large number of parameters, using a large number of entanglements that makes the application on existing hardware challenging. Prospects for rapid improvements with more capable hardware are, however, very encouraging.

Automated summary

We explore the preparation of specific nuclear states on gate-based quantum hardware using variational algorithms. Quantum computing can, in principle, solve large-scale nuclear systems with exponentially fewer resources than classical computing. We use the unitary coupled cluster approach to construct approximations of the ground-state vectors. However, the application on existing hardware is challenging due to the need for minimizing a large number of parameters and using a large number of entanglements.