Measurement of soft zero-pi qubit with parallel-plate capacitors*

Decoherence protection of zero-pi qubits requires maximizing the charge-mode capacitance while simultaneously minimizing the flux-mode capacitance. One major limitation to realizing zero-pi qubits is the stray capacitance caused by the large charge-mode capacitor, which impedes decreasing the flux-mode capacitance. Deviating from the conventional coplanar interdigitated capacitor design, parallel-plate capacitors can be implemented with a much smaller area, achieving the desired large charge-mode capacitance while reducing unwanted stray capacitances. Here, we show the decoherence properties of this zero-pi qubit with parallel-plate capacitors in terms of its susceptibility against charge and flux noise. We discuss offset-charge calibration techniques done with this qubit and will present preliminary results on Raman-based qubit control. Lastly, we discuss a structural variation in the circuit that can potentially implement mode-selective qubit control while maintaining the qubit in the extended parameter regime compared to coplanar designs.