Single-photon emitters in solid-state systems are important building blocks for scalable quantum technologies. Recently, quantum light emitters have been discovered in the wide-gap van der Waals insulator hexagonal boron nitride (hBN). These color centers have attracted considerable attention due to their quantum performance at elevated temperatures and wide range of transition energies. Here, we demonstrate coherent state manipulation of a single hBN color center with ultrafast laser pulses and investigate in our joint experiment–theory study the coupling between the electronic system and phonons. We demonstrate that coherent control can be performed not only resonantly on the optical transition giving access to the decoherence but also phonon-assisted, which reveals the internal phonon quantum dynamics. In the case of optical phonons, we measure their decoherence, stemming in part from their anharmonic decay. Dephasing induced by the creation of acoustic phonons manifests as a rapid decrease in the coherent control signal when traveling phonon wave packets are emitted. Furthermore, we demonstrate that the quantum superposition between a phonon-assisted process and resonant excitation causes ultrafast oscillations of the coherent control signal. Our results pave the way for ultrafast phonon quantum state control on the nanoscale and open up a new promising perspective for hybrid quantum technologies.

中文翻译：

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单个 hBN 色心的共振和声子辅助超快相干控制

固态系统中的单光子发射器是可扩展量子技术的重要组成部分。最近，在宽禁带范德华绝缘体六方氮化硼（hBN）中发现了量子发光体。这些色心因其在高温下的量子性能和宽范围的跃迁能量而引起了相当大的关注。在这里，我们展示了使用超快激光脉冲对单个 hBN 色心进行相干态操纵，并在我们的联合实验中进行了研究——理论研究了电子系统和声子之间的耦合。我们证明，相干控制不仅可以在光学跃迁上进行共振，从而获得退相干，还可以在声子辅助下进行，这揭示了内部声子量子动力学。在光学声子的情况下，我们测量它们的退相干性，部分源于它们的非谐衰减。当发射声子波包时，由声子的产生引起的相移表现为相干控制信号的快速下降。此外，我们证明了声子辅助过程和共振激发之间的量子叠加导致相干控制信号的超快振荡。我们的结果为纳米尺度上的超快声子量子态控制铺平了道路，并为混合量子技术开辟了新的前景。我们证明了声子辅助过程和共振激发之间的量子叠加导致相干控制信号的超快振荡。我们的结果为纳米尺度上的超快声子量子态控制铺平了道路，并为混合量子技术开辟了新的前景。我们证明了声子辅助过程和共振激发之间的量子叠加导致相干控制信号的超快振荡。我们的结果为纳米尺度上的超快声子量子态控制铺平了道路，并为混合量子技术开辟了新的前景。