Superconducting circuit protected by two-Cooper-pair tunneling

W. C. Smith, A. Kou, X. Xiao, U. Vool, M. H. Devoret

Published 2019-05-03Version 1

We present a protected superconducting qubit based on an effective circuit element that only allows pairs of Cooper pairs to tunnel. These dynamics give rise to a nearly degenerate ground state manifold indexed by the parity of tunneled Cooper pairs. We show that, when the circuit element is shunted by a large capacitance, this manifold can be used as a logical qubit that we expect to be insensitive to multiple relaxation and dephasing mechanisms.