Nanomolecular assemblies of C$_{60}$ can be synthesized to enclose dipolar molecules. The low-temperature states of such endofullerenes are described by quantum mechanical rotors, which are candidates for quantum information devices with higher-dimensional local Hilbert spaces. The experimental exploration of endofullerene arrays comes at a time when machine learning techniques are rapidly being adopted to characterize, verify, and reconstruct quantum states from measurement data. In this paper, we develop a strategy for reconstructing the ground state of chains of dipolar rotors using restricted Boltzmann machines (RBMs) adapted to train on data from higher-dimensional Hilbert spaces. We demonstrate accurate generation of energy expectation values from an RBM trained on data in the free-rotor eigenstate basis, and explore the learning resources required for various chain lengths and dipolar interaction strengths. Finally, we show evidence for fundamental limitations in the accuracy achievable by RBMs due to the difficulty in imposing symmetries in the sampling procedure. We discuss possible avenues to overcome this limitation in the future, including the further development of autoregressive models such as recurrent neural networks for the purposes of quantum state reconstruction.
Optimal control of interacting quantum systems based on the first-order Magnus approximation: Application to multiple dipole-dipole coupled molecular rotors
Optical centrifuge as a probe of strong dissipative coupling between a molecular rotor and superfluid helium
The University of British Columbia（不列颠哥伦比亚大学）；Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究所）；University of Zagreb（萨格勒布大学）；Aarhus University（奥胡斯大学）
A linear rotor trapped and coupled to the vibrational modes of an ion crystal
Freie Universität Berlin（柏林自由大学）；Universidad de Granada（格拉纳达大学）；Helmholtz Institut Mainz（美因茨赫尔姆霍兹研究所）；GSI Helmholtzzentrum für Schwerionenforschung GmbH（GSI重离子研究中心）；Johannes Gutenberg University（约翰内斯·古腾堡大学）
Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances
各向异性是粒子相互作用的基本性质。它在冷和超冷分子过程中占据核心作用，其中已经发现长程力显著依赖于超冷极性分子碰撞中的取向。最近的实验表明，出现的量子现象，如散射共振在冷碰撞制度由于量子化的分子间的自由度。虽然这些状态已被证明是敏感的相互作用的细节，各向异性的量子共振的影响，迄今为止，逃避实验观察。在这里，我们通过改变分子内部转子的量子态，利用量子共振直接测量原子-分子相互作用的各向异性。我们观察到，只有当分子受到旋转激发时，分子氢与亚稳态氦的潘宁电离才会出现碰撞能量为$k_B$ x 270 mK的量子散射共振。我们使用最先进的从头算和多通道量子分子动力学计算表明，各向异性有助于有效的相互作用，只有$H_2$分子在第一激发旋转状态，而旋转基态$H_2$相互作用纯粹各向同性与亚稳态氦。控制内部分子旋转的量子态，使我们能够打开或关闭各向异性，从而解开相互作用的各向同性和各向异性部分。这些量子现象为最先进的理论描述提供了一个具有挑战性的基准，突出了使用冷碰撞来推进粒子相互作用的微观理解的优势。
