Superconducting qubit without Josephson junctions manipulated by orbital angular momentum of light

Previous superconducting qubits have used Josephson junctions as an essential part which gives anharmonicity to make well-separated energy-level spacings. However, since a superconductor ring without Josephson junctions has intrinsically well-separated energy-level spacings, Josephson junctions are not necessary as long as one can achieve single-qubit operations. We show that orbital angular momentum (OAM) of light can be adopted as a qubit-control means and can eliminate the need of Josephson junctions. We provide theoretical analysis for the interaction between a superconducting ring and OAM of light. Feasibility study reveals that the proposed qubit has many advantages over the previous ones.