Single-Shot Readout of a Superconducting Qubit Using a Thermal Detector

TL;DR

This paper demonstrates a novel single-shot readout method for superconducting qubits using a thermal nanobolometer instead of traditional parametric amplifiers, showing promising fidelity and scalability potential.

Contribution

It introduces the use of an ultrasensitive bolometer for qubit readout, providing a scalable alternative to parametric amplifiers in quantum computing.

Findings

Achieved a single-shot fidelity of 0.618 with 13.9 μs readout time.

Fidelity could reach 0.927 without T1 relaxation errors.

Potential for faster readout with improved chip design and absorber materials.

Abstract

Measuring the state of qubits is one of the fundamental operations of a quantum computer. Currently, state-of-the-art high-fidelity single-shot readout of superconducting qubits relies on parametric amplifiers at the millikelvin stage. However, parametric amplifiers are challenging to scale beyond hundreds of qubits owing to practical size and power limitations. Nanobolometers have a multitude of properties that are advantageous for scalability and have recently shown sensitivity and speed promising for qubit readout, but such thermal detectors have not been demonstrated for this purpose. In this work, we utilize an ultrasensitive bolometer in place of a parametric amplifier to experimentally demonstrate single-shot qubit readout. With a readout duration of $13.9~\mu\mathrm{s}$, we achieve a single-shot fidelity of 0.618 which is mainly limited by the energy relaxation time of the qubit, $T_1 = 28~\mu\mathrm{s}$. Without the $T_1$ errors, we find the fidelity to be 0.927. In the future, high-fidelity single-shot readout may be achieved by straightforward improvements to the chip design and experimental setup, and perhaps most interestingly by the change of the bolometer absorber material to reduce the readout time to the hundred-nanosecond level and beyond.