Charge-parity qubits based on concatenation of π-periodic Josephson elements: Part 2

For charge-parity qubits formed from concatenated π-periodic plaquette elements, the dispersion of the qubit energy bands with flux depends on the path through the multi-dimensional flux bias space. With only one plaquette biased near π-periodicity, the dispersion is linear near frustration, while biasing two concatenated plaquettes near π-periodicity results in a quadratic dispersion. Here, we describe our experimental characterization of devices with three concatenated π-periodic elements through spectroscopy and time-domain measurements at various flux and charge bias regimes.