Transformed Dissipation in Superconducting Quantum Circuits

Understand

Superconducting quantum circuits must be designed carefully to avoid dissipation from coupling to external control circuitry.

• Here we introduce the concept of current transformation to quantify coupling to the environment.
• We test this theory with an experimentally-determined impedance transformation of $\sim 10^5$ and find quantitative agreement better than a factor of 2 between this transformation and the reduced lifetime of a phase qubit coupled to a tunable transformer.
• Higher-order corrections from quantum fluctuations are also calculated with this theory, but found not to limit the qubit lifetime.