Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL University, Sorbonne Université, 11 Place Marcelin Berthelot, 75005, Paris, France.
Department of Physics, ETH Zurich, 8093, Zurich, Switzerland.
Nat Commun. 2018 Nov 23;9(1):4955. doi: 10.1038/s41467-018-07433-1.
Coherent superposition states of a mesoscopic quantum object play a major role in our understanding of the quantum to classical boundary, as well as in quantum-enhanced metrology and computing. However, their practical realization and manipulation remains challenging, requiring a high degree of control of the system and its coupling to the environment. Here, we use dysprosium atoms-the most magnetic element in its ground state-to realize coherent superpositions between electronic spin states of opposite orientation, with a mesoscopic spin size J = 8. We drive coherent spin states to quantum superpositions using non-linear light-spin interactions, observing a series of collapses and revivals of quantum coherence. These states feature highly non-classical behavior, with a sensitivity to magnetic fields enhanced by a factor 13.9(1.1) compared to coherent spin states-close to the Heisenberg limit 2J = 16-and an intrinsic fragility to environmental noise.
介观量子物体的相干叠加态在我们理解量子到经典边界、量子增强计量学和计算方面起着重要作用。然而，它们的实际实现和操纵仍然具有挑战性，需要对系统及其与环境的耦合进行高度控制。在这里，我们使用镝原子——基态最具磁性的元素——实现了相反取向的电子自旋态之间的相干叠加，介观自旋大小为 J=8。我们使用非线性光-自旋相互作用驱动相干自旋态到量子叠加，观察到一系列量子相干的崩塌和复苏。这些状态具有高度非经典的行为，与相干自旋态相比，对磁场的灵敏度提高了 13.9(1.1)倍，接近海森堡极限 2J=16，并且对环境噪声具有内在的脆弱性。
