Reducing Spontaneous Emission in Circuit Quantum Electrodynamics by a Combined Readout/Filter Technique

TL;DR

This paper introduces a combined filtering and dispersive coupling technique in circuit QED that enhances qubit lifetime while maintaining fast, high-fidelity readout, compatible with current experimental setups.

Contribution

The authors propose a novel integrated circuit design that simultaneously reduces spontaneous emission and enables efficient qubit measurement in superconducting quantum systems.

Findings

The device operates effectively with current experimental parameters.

It achieves longer qubit lifetimes without sacrificing measurement speed.

The approach is applicable to superconducting qubits in circuit QED.

Abstract

Physical implementations of qubits can be extremely sensitive to environmental coupling, which can result in decoherence. While efforts are made for protection, coupling to the environment is necessary to measure and manipulate the state of the qubit. As such, the goal of having long qubit energy relaxation times is in competition with that of achieving high-fidelity qubit control and measurement. Here we propose a method that integrates filtering techniques for preserving superconducting qubit lifetimes together with the dispersive coupling of the qubit to a microwave resonator for control and measurement. The result is a compact circuit that protects qubits from spontaneous loss to the environment, while also retaining the ability to perform fast, high-fidelity readout. Importantly, we show the device operates in a regime that is attainable with current experimental parameters and provide a specific example for superconducting qubits in circuit quantum electrodynamics.