SciPost Submission Page
Effects of electron-electron interaction and spin-orbit coupling on Andreev pair qubits in quantum dot Josephson junctions
by Teodor Iličin, Rok Žitko
Submission summary
| Authors (as registered SciPost users): | Rok Žitko |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2512.23015v2 (pdf) |
| Code repository: | https://doi.org/10.5281/zenodo.4841075 |
| Data repository: | https://doi.org/10.5281/zenodo.18260459 |
| Date submitted: | Jan. 15, 2026, 7:02 p.m. |
| Submitted by: | Rok Žitko |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
The author(s) disclose that the following generative AI tools have been used in the preparation of this submission:
Text improvements in the manuscript for grammar, clarity and conciseness. ChatGPT 5.2, Dec 2025.
Abstract
We investigate the superconducting Anderson impurity model for interacting quantum dot Josephson junctions with spin-orbit coupling and a term accounting for tunnelling through higher-energy orbitals. These elements establish the conditions required for spin polarization in the absence of external magnetic field at finite superconducting phase bias. This Hamiltonian has been previously used to model the Andreev spin qubit, where quantum information is encoded in spinful odd-parity subgap states. Here we instead analyse the even-parity sector, i.e., the Andreev pair qubit based on Andreev bound states (ABS). The model is solved using the zero-bandwidth approximation and the numerical renormalization group, with further insight from variational calculations. Electron-electron interaction admixes single-occupancy Yu-Shiba-Rusinov (YSR) components into the ABS states, thereby strongly enhancing spin transitions in the presence of spin-orbit coupling. The ABS states can thus become sensitive to local magnetic field fluctuations, which has implications for decoherence in Andreev pair qubits. For strong interaction $U$, especially in the cross-over region between the ABS and YSR regimes for $U \sim 2Δ$, charge, spin, and inductive transitions can all become strong, offering avenues for spin control and quantum transduction.
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