通过核自旋超极化增强光地址分子量子比特的自旋相干性
Enhancing Spin Coherence of Optically-Addressed Molecular Qubit by Nuclear Spin Hyperpolarization
AI总结：
通过三重动态核极化技术抑制核自旋浴引起的退相干，提升分子量子比特的自旋横向相干时间，实验显示自旋回波衰减时间增强25%，并验证了核极化对相干时间的定量影响。
摘要：
光可调分子三重态自旋提供了一种化学可调的量子应用平台，但其相干性常受限于与周围自旋浴的相互作用。本文展示通过三重动态核极化（三重-DNP）超极化质子自旋浴，抑制核自旋产生的磁噪声，从而延长电子自旋横向相干时间。实验发现，当质子自旋浴极化率达60%时，自旋回波衰减时间增强25%。测量的自旋回波衰减时间（T₂）与核极化量的标度关系定量符合由极化控制的核二阶矩预测的依赖关系。两者均通过簇相关展开（CCE）模拟定量重现。这些结果证明核自旋超极化是一种通用且可主动调节的方法，用于分子量子比特的相干工程。本工作提供了一种广泛适用的设计框架，用于高相干分子和固态自旋系统。
英文摘要：
Optically addressable molecular triplet spins provide a chemically tunable platform for quantum application, but their coherence is often limited by interactions with surrounding spin baths. Here we demonstrate controlled suppression of nuclear-bath-induced decoherence in photoexcited triplet spins of pentacene co-crystallized in high-purity naphthalene single crystals. By hyperpolarizing the proton spin bath through triplet dynamic nuclear polarization (triplet-DNP), magnetic noise generated by the nuclear spins is suppressed, leading to an extension of the electron spin transverse coherence time. Experimentally, we observe a 25\% enhancement of the spin-echo decay time with $60\%$ polarization of the proton spin bath. The measured scaling of the spin-echo decay time ($T_2$) with nuclear polarization quantitatively follows the predicted dependence derived from the polarization-controlled nuclear second moment. Both the enhancement and the absolute value of the coherence time are quantitatively reproduced by cluster correlation expansion (CCE) simulations. These results establish nuclear spin hyperpolarization as a general and actively tunable approach to engineering coherence in molecular qubits. This work provides a broadly applicable design framework for high-coherence molecular and solid-state spin systems.
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