Superconducting qubit readout using a thermal detector

Abstract: 

Currently, state-of-the-art high-fidelity single-shot readout of superconducting qubits relies on parametric amplifiers at the millikelvin stage. However, scaling parametric amplifiers beyond hundreds of qubits is challenging due to practical size and power limitations. In this work, we utilize an ultrasensitive thermal detector, a so-called nanobolometer, in place of a parametric amplifier to perform qubit readout. Such bolometers have several properties that are advantageous for scalability. In an initial proof of concept experiment, we achieve single-shot readout with a fidelity of 1 - P(g|e) - P(e|g) = 0.618 with a readout duration of 13.9µs. In addition to single-shot readout, I will present preliminary results on multiplexed readout using multiple bolometers on the same chip, and a clear pathway to increasing the readout fidelity to the level of 0.999 with an integration time on the order of 100 nanoseconds.