Broadband Filters for Abatement of Spontaneous Emission in Circuit Quantum Electrodynamics

TL;DR

This paper presents a broadband filter design using impedance engineering to improve qubit readout speed and fidelity by suppressing spontaneous emission at the qubit frequency while allowing photon escape at the cavity frequency.

Contribution

It introduces a novel broadband filter for circuit QED that enhances qubit readout performance by selectively filtering spontaneous emission pathways.

Findings

Effective suppression of spontaneous emission at qubit frequency.

Successful implementation of the broadband filter in on-chip and off-chip setups.

Improved qubit measurement fidelity and speed.

Abstract

The ability to perform fast, high-fidelity readout of quantum bits (qubits) is essential to the goal of building a quantum computer. However, coupling a fast measurement channel to a superconducting qubit typically also speeds up its relaxation via spontaneous emission. Here we use impedance engineering to design a filter by which photons may easily leave the resonator at the cavity frequency but not at the qubit frequency. We implement this broadband filter in both an on-chip and off-chip configuration.