Multiplexed Readout of Superconducting Qubits Using a 3D Re-entrant Cavity Filter

TL;DR

This paper introduces a 3D re-entrant cavity filter for frequency-multiplexed readout of superconducting qubits, enabling scalable, high-fidelity measurements crucial for quantum error correction.

Contribution

It presents a novel cavity filter design that is scalable and can be integrated with large qubit arrays for efficient quantum state readout.

Findings

Successfully demonstrated multiplexed readout of four qubits

Achieved high-fidelity measurements with the cavity filter

The design can be scaled to larger qubit arrays

Abstract

Hardware efficient methods for high fidelity quantum state measurements are crucial for superconducting qubit experiments, as qubit numbers grow and feedback and state reset begin to be employed for quantum error correction. We present a 3D re-entrant cavity filter designed for frequency-multiplexed readout of superconducting qubits. The cavity filter is situated out of the plane of the qubit circuit and capacitively couples to an array of on-chip readout resonators in a manner that can scale to large qubit arrays. The re-entrant cavity functions as a large-linewidth bandpass filter with intrinsic Purcell filtering. We demonstrate the concept with a four-qubit multiplexed device.