Coupled superconducting spin qubits with spin-orbit interaction

TL;DR

This paper theoretically analyzes the interaction between superconducting spin qubits influenced by spin-orbit interaction, revealing tunable quantum gate mechanisms and proposing a scalable qubit network for quantum computing.

Contribution

It introduces a detailed theoretical model of coupled superconducting spin qubits with spin-orbit interaction, identifying tunable interactions for quantum gate implementation.

Findings

Effective qubit interactions include Ising, Heisenberg, and Dzyaloshinskii-Moriya types.

Interaction can be tuned via superconducting phase difference, tunnel barrier, and SOI parameters.

Fast controlled phase-flip gates with >99.99% fidelity are achievable.

Abstract

Superconducting spin qubits, also known as Andreev spin qubits, promise to combine the benefits of superconducting qubits and spin qubits defined in quantum dots. While most approaches to control these qubits rely on controlling the spin degree of freedom via the supercurrent, superconducting spin qubits can also be coupled to each other via the superconductor to implement two-qubit quantum gates. We theoretically investigate the interaction between superconducting spin qubits in the weak tunneling regime and concentrate on the effect of spin-orbit interaction (SOI), which can be large in semiconductor-based quantum dots and thereby offers an additional tuning parameter for quantum gates. We find analytically that the effective interaction between two superconducting spin qubits consists of Ising, Heisenberg, and Dzyaloshinskii-Moriya interactions and can be tuned by the superconducting phase difference, the tunnel barrier strength, or the SOI parameters. The Josephson current becomes dependent on SOI and spin orientations. We demonstrate that this interaction can be used for fast controlled phase-flip gates with a fidelity >99.99%. We propose a scalable network of superconducting spin qubits which is suitable for implementing the surface code.