Tunable coupling of qubits: Nonadiabatic correctionsCarsten Hutter1, Alexander Shnirman1, Yuriy Makhlin2 and Gerd Schön1
1 Institut für Theoretische Festkörperphysik and DFG-Center for Functional Nanostructures (CFN), Universität Karlsruhe D-76128 Karlsruhe, Germany
2 Landau Institute for Theoretical Physics - Kosygin st. 2, 119334 Moscow, Russia
received 6 February 2006; accepted in final form 21 April 2006
published online 17 May 2006
We analyze the coupling of qubits mediated by a tunable and fast element beyond the adiabatic approximation. The nonadiabatic corrections are important and even dominant in parts of the relevant parameter range. As an example, we consider the tunable capacitive coupling between two charge qubits mediated by a gated Josephson junction, as suggested by Averin and Bruder. The nonadiabatic, inductive contribution persists when the capacitive coupling is tuned to zero. On the other hand, the total coupling can be turned off (in the rotating-wave approximation) if the qubits are operated at symmetry points.
85.25.Hv - Superconducting logic elements and memory devices; microelectronic circuits.
03.67.Lx - Quantum computation.
© EDP Sciences 2006