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Decoherence due to nodal quasiparticles in $d$-wave qubits

Ya. V. Fominov^ab, A. A. Golubov^a, M. Yu. Kupriyanov<sup>c

a</sup> Department of Applied Physics, University of Twente
^b L. D. Landau Institute for Theoretical Physics, Russian Academy of Sciences
^c Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University

Abstract: We study the Josephson junction between two $d$-wave superconductors, which is discussed as an implementation of a qubit. We propose an approach that allows to calculate the decoherence time due to an intrinsic dissipative process: quantum tunneling between the two minima of the double-well potential excites nodal quasiparticles which lead to incoherent damping of quantum oscillations. The decoherence is weakest in the mirror junction, where the contribution of nodal quasiparticles corresponds to the superohmic dissipation and becomes small at small tunnel splitting of the energy level in the double-well potential. For available experimental data, we estimate the quality factor.

PACS: 73.23.-b, 74.50.+r, 85.25.-j

Received: 21.04.2003

Language: English

 English version: Journal of Experimental and Theoretical Physics Letters, 2003, 77:10, 587–591

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