Protecting a superconducting qubit from energy decay by selection rule engineering

Abstract

Quantum control of atomic systems is largely enabled by the rich structure of selection rules in the spectra of most real atoms. Their macroscopic superconducting counterparts have been lacking this feature, being limited to a single transition type with a large dipole. Here we report a superconducting artificial atom with tunable transition dipoles, designed such that its forbidden (qubit) transition can dispersively interact with microwave photons due to the virtual excitations of allowed transitions. Owing to this effect, we have demonstrated an in-situ tuning of qubit's energy decay lifetime by over two orders of magnitude, exceeding a value of $2~\textrm{ms}$, while keeping the transition frequency fixed around $3.5~\textrm{GHz}$