Mediated tunable coupling of flux qubits
Open Access
- 7 November 2005
- journal article
- Published by IOP Publishing in New Journal of Physics
- Vol. 7, 230
- https://doi.org/10.1088/1367-2630/7/1/230
Abstract
It is sketched how a monostable rf- or dc-SQUID can mediate an inductive coupling between two adjacent flux qubits. The nontrivial dependence of the SQUID's susceptibility on external flux makes it possible to continuously tune the induced coupling from antiferromagnetic (AF) to ferromagnetic (FM). In particular, for suitable parameters, the induced FM coupling can be sufficiently large to overcome any possible direct AF inductive coupling between the qubits. The main features follow from a classical analysis of the multi-qubit potential. A fully quantum treatment yields similar results, but with a modified expression for the SQUID susceptibility. Since the latter is exact, it can also be used to evaluate the susceptibility--or, equivalently, energy-level curvature--of an isolated rf-SQUID for larger shielding and at degenerate flux bias, i.e., a (bistable) qubit. The result is compared to the standard two-level (pseudospin) treatment of the anticrossing, and the ensuing conclusions are verified numerically.Keywords
All Related Versions
This publication has 15 references indexed in Scilit:
- Hamiltonian for coupled flux qubitsPhysical Review B, 2005
- Entangling flux qubits with a bipolar dynamic inductancePhysical Review B, 2004
- Evidence for Entangled States of Two Coupled Flux QubitsPhysical Review Letters, 2004
- Multilevel quantum description of decoherence in superconducting qubitsPhysical Review B, 2004
- Variable Electrostatic Transformer: Controllable Coupling of Two Charge QubitsPhysical Review Letters, 2003
- Entangled Macroscopic Quantum States in Two Superconducting QubitsScience, 2003
- Quantum oscillations in two coupled charge qubitsNature, 2003
- Quantum Computation with Untunable CouplingsPhysical Review Letters, 2002
- Quantum-state engineering with Josephson-junction devicesReviews of Modern Physics, 2001
- Josephson Persistent-Current QubitScience, 1999