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TT: Tiefe Temperaturen

TT 13: Transport - Quantum Coherence and Quantum Information Systems

TT 13.11: Vortrag

Samstag, 5. März 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 σ_yσ_y [1] or σ_xσ_x [2,3] terms in the charge basis. In the latter case the interaction term commutes with the single-qubit Hamiltonian at the degeneracy point, ∝ E_J σ_x. 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).