Superconducting circuit protected by two-Cooper-pair tunneling

AbstractWe present a protected superconducting qubit based on an effective circuit element that only allows pairs of Cooper pairs to tunnel.

Key Results

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.