Fully robust qubit in atomic and molecular three-level systems

TL;DR

This paper introduces a simplified method to create a fully robust qubit in a three-level atomic or molecular system using continuous driving fields, significantly enhancing coherence times and enabling high-frequency quantum sensing.

Contribution

The authors demonstrate that only three levels are needed to construct a fully robust qubit, reducing complexity compared to previous four-level schemes, and analyze its implementation in NV-centers in diamond.

Findings

Achieves over two orders of magnitude improvement in coherence time.

Provides a practical scheme for robust qubits in atomic and solid-state systems.

Enables high-frequency quantum sensing applications.

Abstract

We present a new method of constructing a fully robust qubit in a three-level system. By the application of continuous driving fields, robustness to both external and controller noise is achieved. Specifically, magnetic noise and power fluctuations do not operate within the robust qubit subspace. Whereas all the continuous driving based constructions of such a fully robust qubit considered so far have required at least four levels, we show that in fact only three levels are necessary. This paves the way for simple constructions of a fully robust qubit in many atomic and solid state systems that are controlled by either microwave or optical fields. We focus on the NV-center in diamond and analyze the implementation of the scheme, by utilizing the electronic spin sub-levels of its ground state. In current state-of-the-art experimental setups the scheme leads to improvement of more than two orders of magnitude in coherence time, pushing it towards the lifetime limit. We show how the fully robust qubit can be used to implement quantum sensing, and in particular, the sensing of high frequency signals.