Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 20: Transport: Quantum Coherence and Quantum Information Systems 3 (jointly with MA and HL)
TT 20.3: Talk
Tuesday, March 27, 2012, 10:15–10:30, BH 243
Coulomb-assisted braiding of Majorana fermions in a Josephson junction array — •Fabian Hassler1, Bernard Van Heck2, Anton Akhmerov2, Michele Burrello2, and Carlo Beenakker2 — 1Institute for Quantum Information, RWTH Aachen University, D-52056 Aachen, Germany — 2Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands
We show how to exchange (braid) Majorana fermions in a network of superconducting nanowires by control over Coulomb interactions rather than tunneling. Even though Majorana fermions are charge-neutral quasiparticles (equal to their own antiparticle), they have an effective long-range interaction through the even-odd electron number dependence of the superconducting ground state. The flux through a split Josephson junction controls this interaction via the ratio of Josephson and charging energies, with exponential sensitivity. By switching the interaction on and off in neighboring segments of a Josephson junction array, the non-Abelian braiding statistics can be realized without the need to control tunnel couplings by gate electrodes. This is a solution to the problem how to operate on topological qubits when gate voltages are screened by the superconductor.