### Session N1: Topological Phases and Quantum Computing

8:00 AM–11:00 AM, Wednesday, March 15, 2006
Baltimore Convention Center Room: Ballroom IV

Chair: Eduardo Fradkin, University of Illinois

Abstract ID: BAPS.2006.MAR.N1.1

### Abstract: N1.00001 : Protected qubits and quantum computation using Josephson junctions

8:00 AM–8:36 AM

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#### Author:

Alexei Kitaev
(Caltech \& Microsoft)

Several schemes of topological protection have been proposed, in which qubits are realized as degenerate ground states of quantum many-body systems so that all likely perturbations are exponentially suppressed. In the realm of Josephson junction physics, this approach was pioneered by Doucot, Vidal, Ioffe, and Feigelman in 2002. I will report a variation of their scheme that offers greater robustness and flexibility. Its key element is a quantum transformer'', a superconducting current mirror operated in the quantum regime. This is a four-terminal device whose energy depends only on $\phi_1-\phi_2+\phi_3-\phi_4$, with exponentially small error terms'' like $\cos(\phi_1-\phi_4)$. The qubit is implemented by connecting terminal $1$ with $3$ and $2$ with $4$. I will describe a realization of the basic element, qubit measurements and unitary gates, and also discuss some parameter tradeoffs.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.N1.1