Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, I-43124, Parma, Italy.
INFN, Sezione di Milano-Bicocca, gruppo collegato di Parma, I-43124, Parma, Italy.
Nat Commun. 2023 Mar 24;14(1):1653. doi: 10.1038/s41467-023-36852-y.
Improving the performance of molecular qubits is a fundamental milestone towards unleashing the power of molecular magnetism in the second quantum revolution. Taming spin relaxation and decoherence due to vibrations is crucial to reach this milestone, but this is hindered by our lack of understanding on the nature of vibrations and their coupling to spins. Here we propose a synergistic approach to study a prototypical molecular qubit. It combines inelastic X-ray scattering to measure phonon dispersions along the main symmetry directions of the crystal and spin dynamics simulations based on DFT. We show that the canonical Debye picture of lattice dynamics breaks down and that intra-molecular vibrations with very-low energies of 1-2 meV are largely responsible for spin relaxation up to ambient temperature. We identify the origin of these modes, thus providing a rationale for improving spin coherence. The power and flexibility of our approach open new avenues for the investigation of magnetic molecules with the potential of removing roadblocks toward their use in quantum devices.
提高分子量子比特的性能是释放第二次量子革命中分子磁性的关键里程碑。由于振动导致的自旋弛豫和退相干的控制对于达到这一里程碑至关重要，但这受到我们对振动的性质及其与自旋的耦合缺乏理解的阻碍。在这里，我们提出了一种协同方法来研究一个典型的分子量子比特。它结合了非弹性 X 射线散射来测量晶体主要对称方向上的声子色散和基于 DFT 的自旋动力学模拟。我们表明，晶格动力学的经典德拜图像不再适用，而能量在 1-2meV 之间的分子内振动在环境温度下对自旋弛豫有很大的影响。我们确定了这些模式的起源，从而为提高自旋相干性提供了依据。我们的方法具有强大的功能和灵活性，为研究磁性分子开辟了新的途径，有可能消除其在量子器件中的应用障碍。
