近日，英国杜伦大学的Philip D. Gregory&Simon L.Cornish及其研究小组取得一项新进展。经过不懈努力，他们揭示超冷极性分子气体中的二级旋转相干性和偶极相互作用。相关研究成果已于2024年1月17日在国际知名学术期刊《自然—物理学》上发表。
该研究团队在缺乏偶极-偶极相互作用的情况下，成功证明了87Rb133Cs分子的旋转魔法光势阱可以支持长达0.78(4)s的拉姆齐相干时间。据估计，使用单个自旋回波脉冲，相干时间可延长至超过1.4秒，置信水平为95%。在所研究的势阱中，偶极相互作用成为拉姆齐对比在产生振荡偶极子的叠加态中丢失的主要机制。通过调整叠加态中的状态，研究人员能够调整有效偶极矩，并观察到相干时间与偶极相互作用的强度成反比。这项研究工作为量子计算和量子模拟释放了分子旋转自由度的全部潜力。
据悉，超冷极性分子结合了丰富的长寿命内部状态结构和可控的远距离各向异性偶极子-偶极子相互作用。特别是，当极性分子被限制在光镊或光晶格中时，它们的旋转态可以用于编码用于量子计算的相互作用量子比特或用于模拟量子磁性的伪自旋。与所有量子平台一样，鲁棒相干叠加态的工程至关重要。然而，对于光捕获分子，旋转态之间的相干时间通常受到不均匀微分光移的限制。
附：英文原文
Title: Second-scale rotational coherence and dipolar interactions in a gas of ultracold polar molecules
Author: Gregory, Philip D., Fernley, Luke M., Tao, Albert Li, Bromley, Sarah L., Stepp, Jonathan, Zhang, Zewen, Kotochigova, Svetlana, Hazzard, Kaden R. A., Cornish, Simon L.
Issue&Volume: 2024-01-17
Abstract: Ultracold polar molecules combine a rich structure of long-lived internal states with access to controllable long-range anisotropic dipole–dipole interactions. In particular, the rotational states of polar molecules confined in optical tweezers or optical lattices may be used to encode interacting qubits for quantum computation or pseudo-spins for simulating quantum magnetism. As with all quantum platforms, the engineering of robust coherent superpositions of states is vital. However, for optically trapped molecules, the coherence time between rotational states is typically limited by inhomogeneous differential light shifts. Here we demonstrate a rotationally magic optical trap for 87Rb133Cs molecules that supports a Ramsey coherence time of 0.78(4) s in the absence of dipole–dipole interactions. This is estimated to extend to >1.4 s at the 95% confidence level using a single spin-echo pulse. In our trap, dipolar interactions become the dominant mechanism by which Ramsey contrast is lost for superpositions that generate oscillating dipoles. By changing the states forming the superposition, we tune the effective dipole moment and show that the coherence time is inversely proportional to the strength of the dipolar interaction. Our work unlocks the full potential of the rotational degree of freedom in molecules for quantum computation and quantum simulation.
DOI: 10.1038/s41567-023-02328-5
Source: https://www.nature.com/articles/s41567-023-02328-5