Galvanic coupling of flux qubits: simple theory and tunability
Abstract
Galvanic coupling of small-area (three-junction) flux qubits, using shared large Josephson junctions, has been shown to yield appreciable interaction strengths in a flexible design, which does not compromise the junctions' intrinsic good coherence properties. For an introduction, I recapitulate an elementary derivation of the coupling strength, which is subsequently generalized to the case of tunable coupling for a current-biased shared junction. While the ability to vary coupling constants by, say, 20% would be useful in experiments, sign-tunability (implying switchability) is highly preferable for several quantum-computing paradigms. This note sketches two ideas: a "crossbar" design with competing ferro- and antiferromagnetic current-biased tunable couplings, and a "mediated" one involving an extra loop between the qubits. The latter is a variation on proposals for tunable capacitive coupling of charge qubits, and tunable inductive coupling of large-area flux qubits.
Keywords
Cite
@article{arxiv.cond-mat/0605398,
title = {Galvanic coupling of flux qubits: simple theory and tunability},
author = {Alec Maassen van den Brink},
journal= {arXiv preprint arXiv:cond-mat/0605398},
year = {2007}
}
Comments
REVTeX4, 8 pp., 3 figs. built into the LaTeX source; informal note, comments welcome; N.B. "Alec" is my first, and "Maassen van den Brink" my family name