A team of researchers has demonstrated the ability to coherently manipulate quantum states in a hybrid system combining a diamond nitrogen-vacancy (NV) center with a magnetic topological insulator. This advance, utilizing Floquet engineering, allows for the control of interactions between the NV center spins and the magnetic excitations of the topological material, known as magnons. The novelty lies in the ability to tune these interactions using a microwave field, opening new avenues for the design of quantum devices.

The study addresses a fundamental challenge in condensed matter physics and quantum information: the integration of quantum systems with exotic magnetic properties. Magnetic topological insulators, such as the Cr-BST used in this work, possess magnetic excitations with robust properties promising for information transport. However, coupling and controlling these excitations with well-characterized qubits, such as NV centers, has been a complex task. The Floquet engineering technique, which involves applying periodic oscillating fields to modify the effective properties of a quantum system, offers an elegant solution to this problem.

By microwave irradiation, the researchers managed to modulate the interaction between the NV center spin and the magnons of the Cr-BST. This allowed them to observe coherent and tunable coupling, a crucial step for quantum information transfer between different subsystems. The ability to dynamically and precisely control this coupling is essential for the development of hybrid quantum architectures, where NV centers could act as information processors and topological insulators as storage or transport media. This work lays the groundwork for future research in spin-based quantum computing and quantum spintronics.