Coupling Spin Qubits via Superconductors

Martin Leijnse and Karsten Flensberg
Phys. Rev. Lett. 111, 060501 – Published 6 August 2013

Abstract

We show how superconductors can be used to couple, initialize, and read out spatially separated spin qubits. When two single-electron quantum dots are tunnel coupled to the same superconductor, the singlet component of the two-electron state partially leaks into the superconductor via crossed Andreev reflection. This induces a gate-controlled singlet-triplet splitting which, with an appropriate superconductor geometry, remains large for dot separations within the superconducting coherence length. Furthermore, we show that when two double-dot singlet-triplet qubits are tunnel coupled to a superconductor with finite charging energy, crossed Andreev reflection enables a strong two-qubit coupling over distances much larger than the coherence length.

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  • Received 14 March 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.060501

© 2013 American Physical Society

Authors & Affiliations

Martin Leijnse and Karsten Flensberg

  • Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark

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Vol. 111, Iss. 6 — 9 August 2013

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