Berlin 2005 – scientific programme
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TT: Tiefe Temperaturen
TT 13: Transport - Quantum Coherence and Quantum Information Systems
TT 13.11: Talk
Saturday, March 5, 2005, 11:30–11:45, TU H3027
Inductively coupled charge qubits with asymmetric SQUIDs — •Carsten Hutter1, Yuriy Makhlin2, Alexander Shnirman1, and Gerd Schön1 — 1Institut für Theoretische Festkörperphysik, Universität Karlsruhe — 2Landau Institute for Theoretical Physics, Moscow, Russia
We investigate various methods of inductive coupling of SQUIDs used as charge qubits. For symmetric SQUIDs, this coupling produces σyσy [1] or σxσx [2,3] terms in the charge basis. In the latter case the interaction term commutes with the single-qubit Hamiltonian at the degeneracy point, ∝ EJ σx. We analyze the stability of the interaction with respect to asymmetries of the parameters of junctions in SQUIDs and find, that the interaction term ceases to commute with the single-qubit Josephson terms, when the symmetry is lifted.
[1] Yu. Makhlin et al., Nature 398, 305 (1999).
[2] J.Q. You et al., Phys. Rev. Lett. 89, 197902 (2002).
[3] J. Lantz et al., Phys. Rev. B 70, 140507(R) (2004).