Speaker: Haonan Xiong
Advisor: V. Manucharyan
Title: Fluorescence Readout of a Superconducting Qubit Using a Fluxonium Artificial Atom
We report the fluorescence "shelving" readout scheme of atomic physics applied to a multi-level fluxonium artificial atom. Here fluxonium circuit is directly coupled to a waveguide which is in turn smoothly connected to a 50Ohm transmission line, i.e. no high-Q cavity mode is involved. The qubit is encoded into a low-frequency transition 0-1 of fluxonium which is protected from Purcell effect by the cut-off of the waveguide. The readout transition involves higher excited states of fluxonium and is designed to be in the passband of the waveguide. The state of the qubit can be identified by measuring the reflection coefficient at the frequency of the readout transition. We discuss the requirements to achieve a QND measurement in such a system and origins of decoherence. Direct connection of a long-lived qubit to propagating photons can be useful for realizing quantum networks and quantum internet. Our device can also serve as a tool to characterize and optimize thermalization of the measurement lines in superconducting qubit experiments.