Homenucl-tharXiv:2605.30261

Qubit-efficient variational algorithm for nuclear structure

nucl-thquant-ph2026-05v1license

Abstract

In this work, we compare three qubit-mapping strategies to study the structure of the nuclear ground state within the shell model description employing the Variational Quantum Eigensolver (VQE) approach. Although the initial point for different mappings is a Hamiltonian matrix in many-body particle basis or Slater determinant (SD) basis, the structure of the trial wavefunction and resource counts are different for each mapping. These three mappings are tested for a mid pp-shell nucleus 10^{10}B and compared the quantum resources required to find the ground state for each mapping. Further, we extend the qubit-efficient mapping to study the ground state of one more mid pp-shell nucleus 12^{12}C. We run circuits up to 26-qubits representing their ground states on a noisy simulator (IBM's FakeFez backend) and quantum hardware (ibm_fezibm\_fez). The best post-error mitigated results from the hardware for 10^{10}B ground state is obtained following SD to qubit mapping with a percent error of 0.21 \%. The percent errors for the same state following cSD and pnSD mapping are 3.37 and 8.88 \%, respectively. On the other hand, following the cSD mapping, the post-error mitigated ground state energy of 12^{12}C is 6.82 \% away from the exact result. We further evaluate the fidelity of the VQE wavefunctions obtained from hardware with respect to the shell model wavefunctions for the cSD mapping. This cSD mapping can be useful for scaling the VQE algorithm for complex nuclei across different mass regions in terms of qubit efficiency.

Cite

@article{arxiv.2605.30261,
  title  = {Qubit-efficient variational algorithm for nuclear structure},
  author = {Chandan Sarma and Paul Stevenson},
  journal= {arXiv preprint arXiv:2605.30261},
  year   = {2026}
}