Creating qubit states with degenerate two-level systems
Phys. Rev. A 113, 042604 – Published 7 April, 2026
DOI: https://doi.org/10.1103/n284-bpds
Abstract
A qubit, or quantum bit, is conventionally defined as “a physical system for storing information that is capable of existing in either of two quantum states or in a superposition of both” [Oxford English Dictionary (Oxford University Press, 2025)]. In this paper, we examine the simple question of whether two distinct levels, each consisting of multiply degenerate substates, could serve as a practical quantum bit using two fine-structure energy levels containing degeneracy as a model. We find that, in the continuous presence of the field, the atom still undergoes Rabi oscillations, which are suitable for quantum gate construction. In addition, we compute the average fidelity in Hadamard gate performance for a single degenerate atom and postulate the required form of two-atom interaction to construct a controlled- gate.
