Efforts to harness quantum hardware relying on quantum mechanical principles have been steadily progressing. The search for novel material platforms that could spur the progress by providing new functionalities for solving the outstanding technological problems is however still active. Any physical property presenting two distinct energy states that can be found in a long-lived superposition state can serve as a quantum bit (qubit), the basic information processing unit in quantum technologies. Molecular systems that can feature electron and/or nuclear spin states together with optical transitions are one of the material platforms that can serve as optically addressable qubits. The attractiveness of molecular systems for quantum technologies relies on the fact that molecular structures of atomically defined nature can be obtained in endless diversity of chemical compositions. Crucially, by harnessing the molecular design protocols, the optical and spin (electronic and nuclear) properties of molecules can be tailored, aiding the design of optically addressable spin qubits and quantum sensors. In this contribution, we present a concise and collective discussion of optically addressable spin-bearing molecules – namely, organic molecules, transition metal (TM) and rare-earth ion (REI) complexes – and highlight recent results such as chemical tuning of optical and electron spin quantum coherence, optical spin initialization and readout, intramolecular quantum teleportation, optical coherent storage, and photonic-enhanced optical addressing. We envision that optically addressable spin-carrying molecules could become a scalable building block of quantum hardware for applications in the fields of quantum sensing, quantum communication and quantum computing.

中文翻译：

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自旋分子作为量子技术的光学可寻址平台


利用依赖于量子力学原理的量子硬件的努力一直在稳步推进。然而，寻找可以通过提供新功能来解决突出技术问题来刺激进步的新型材料平台仍在积极进行。在长寿命叠加态中可以找到的呈现两种不同能量态的任何物理属性都可以用作量子比特 （qubit），这是量子技术中的基本信息处理单元。可以具有电子和/或核自旋态以及光学跃迁的分子系统是可以用作光学可寻址量子比特的材料平台之一。分子系统对量子技术的吸引力取决于这样一个事实，即原子定义性质的分子结构可以在化学成分的无穷无尽的多样性中获得。至关重要的是，通过利用分子设计协议，可以定制分子的光学和自旋（电子和核）特性，从而有助于设计光学可寻址的自旋量子比特和量子传感器。在这篇文章中，我们简要地讨论了光学寻址的自旋分子——即有机分子、过渡金属 （TM） 和稀土离子 （REI） 配合物——并重点介绍了最近的结果，例如光学和电子自旋量子相干性的化学调谐、光学自旋初始化和读出、分子内量子隐形传态、光学相干存储和光子增强光学寻址。我们设想，光学可寻址的自旋携带分子可以成为量子硬件的可扩展构建块，用于量子传感、量子通信和量子计算领域的应用。