Cloaking a qubit in a cavity

TL;DR

This paper demonstrates a method to decouple a qubit from a cavity in circuit QED by using tailored external driving, effectively cloaking the qubit and improving quantum measurement and control.

Contribution

It introduces a novel technique to engineer light-matter interaction by actively cloaking a qubit, enhancing quantum measurement and coherence in circuit QED systems.

Findings

Cloaking cancels ac-Stark shift.

Cloaking reduces measurement-induced dephasing.

Cloaking accelerates qubit readout.

Abstract

Cavity quantum electrodynamics (QED) uses a cavity to engineer the mode structure of the vacuum electromagnetic field such as to enhance the interaction between light and matter. Exploiting these ideas in solid-state systems has lead to circuit QED which has emerged as a valuable tool to explore the rich physics of quantum optics and as a platform for quantum computation. Here we introduce a simple approach to further engineer the light-matter interaction in a driven cavity by controllably decoupling a qubit from the cavity's photon population, effectively cloaking the qubit from the cavity. This is realized by driving the qubit with an external tone tailored to destructively interfere with the cavity field, leaving the qubit to interact with a cavity which appears to be in the vacuum state. Our experiment demonstrates how qubit cloaking can be exploited to cancel ac-Stark shift and measurement-induced dephasing, and to accelerate qubit readout.