Coupled superconducting spin qubits with spin-orbit interaction

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.

Abnormal magnetoresistance effect in the Nb/Si superconductor–semiconductor heterojunction

“…[1] Quantum computers made of superconducting quantum bit with zero dissipation and near-quantum limit sensitivity are the most promising candidate to overcome the shortcoming. [2][3][4][5][6][7][8] As a result, the artificial superconductor-semiconductor (SSm) heterojunction at nanometer level as a basic structure for superconducting computing element has turned into the widespread international research frontier and hotspot. [11][12][13][14][15] Remarkable results have emerged in the studies of SSm junctions from many aspects.…”

A particle conserving approach to AC-DC driven interacting quantum dots with superconducting leads

“…Several implementations of QD-based Josephson junctions have been devised, including semiconductor nanowires [40] and carbon-based weak links such as nanotubes [5,6,12,[41][42][43][44][45], fullerenes [46], and gated monolayers of graphene [47]. QD-based Josephson junctions have moreover been proposed as a platform for quantum computing, employing Andreev spin qubits [48][49][50][51].…”