High fidelity readout of a transmon qubit using a superconducting low-inductance undulatory galvanometer microwave amplifier

Abstract

We report high-fidelity, quantum non-demolition, single-shot readout of a superconducting transmon qubit using a dc-biased superconducting low-inductance undulatory galvanometer (SLUG) amplifier. The SLUG improves the system signal-to-noise ratio by $6.5\;{\rm dB}$ in a $20\;{\rm MHz}$ window compared with a bare high electron mobility transistor amplifier. An optimal cavity drive pulse is chosen using a genetic search algorithm, leading to a maximum combined readout and preparation fidelity of $91.9\%$ with a measurement time of ${{T}_{{\rm meas}}}=200\;{\rm ns}$ . Using post-selection to remove preparation errors caused by heating, we realize a combined preparation and readout fidelity of $94.3\%$ .

Keywords

• superconducting qubit
• microwave amplifier
• genetic algorithm