Engineered microwave driving field allows to observe Floquet-Raman transition (an analog of Raman transition mediated by Floquet levels) in a solid-state spin system.

We experimentally observe Floquet Raman transitions in the weakly driven solid-state spin system of a nitrogen-vacancy center in diamond. The periodically driven spin system simulates a two-band Wannier-Stark ladder model and allows us to observe coherent spin state transfer arising from a Raman transition mediated by Floquet synthetic levels. It also leads to the prediction of an analog photon-assisted Floquet Raman transition and dynamical localization in a driven two-level quantum system. The demonstrated rich Floquet dynamics offers new capabilities to achieve effective Floquet coherent control of a quantum system with potential applications in various types of quantum technologies based on driven quantum dynamics. In particular, the Floquet Raman system may be used as a quantum simulator for the physics of periodically driven systems.

量子信息科学技术，通过对单个原子、单个电子、单个光子的量子态进行调控与检测，从而实现远超当前技术水平的获取信息、处理信息、传输信息的能力，并有望带来颠覆性的量子技术。对量子物理体系的调控能力和方式的不断提升和发展，是实现量子信息科学技术的核心要素。

目前广泛应用的对原子、自旋量子态的操控方法，主要是基于拉比振荡或者受激拉曼跃迁过程。这两种量子动力学过程需要共振的周期性驱动场或者仅适用于多能级量子体系。11月19日，物理学权威期刊《物理评论快报》（Physical Review Letters）刊发了联合实验室在固态单自旋量子调控方面的最新研究成果：Observation of Floquet Raman transition in a driven solid-state spin system。在该工作中，我们首次在固态单自旋二能级量子体系中观测到了频域上的拉曼跃迁过程（Floquet Raman transition），这一新颖的量子动力学过程提供了一种新的量子调控手段，可应用于多种二能级量子体系的操控，特别是使得以低频失谐场进行有效的量子调控成为可能，有助于推动包括量子传感在内的量子技术的实现。实验观测到的频域上的拉曼跃迁过程，可进一步用来研究量子输运的动力学模型、探究量子绝热条件的有效性等量子动力学中的重要问题。

Link: Observation of Floquet Raman Transition in a Driven Solid-State Spin System, Phys. Rev. Lett. 121, 210501 (2018).