Decoherence in Molecular Electron Spin Qubits: Insights from Quantum Many-Body Simulations
Decoherence in Molecular Electron Spin Qubits: Insights from Quantum Many-Body Simulations
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DOI：
10.1021/acs.jpclett.0c00193
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发表时间：
2020-03-19
影响因子：
5.7
通讯作者：
Zhang, Xiao-Guang
中科院分区：
文献类型：
--
作者：
Chen, Jia;Hu, Cong;Zhang, Xiao-Guang
量子态由波函数描述，其相位不能直接测量，但在干涉和纠缠等量子效应中起着至关重要的作用。相对相位信息的损失，称为退相干，是由量子系统与其环境之间的相互作用引起的。退相干可能是通往可靠量子计算道路上最大的障碍。在这里，我们通过对典型磁性分子中中心电子自旋量子比特与附近核自旋相互作用的理论研究，表明退相干即使在孤立的分子中也会发生，尽管并非所有的相位信息都会丢失。剩余相干性是分子依赖的，它为解释实验提出的核自旋扩散势垒提供了微观上的合理化。附近分子对退相干的贡献对分离具有重要的依赖性，在中距离处达到峰值。远处的分子只影响长期的行为。由于剩余相干性计算简单，且与相干时间有很好的相关性，因此可以作为磁性分子相干性的描述符。这项工作将有助于建立增强分子自旋量子比特相干性的设计原则，并有助于激发进一步的理论工作。
Quantum states are described by wave functions whose phases cannot be directly measured but which play a vital role in quantum effects such as interference and entanglement. The loss of the relative phase information, termed decoherence, arises from the interactions between a quantum system and its environment. Decoherence is perhaps the biggest obstacle on the path to reliable quantum computing. Here we show that decoherence occurs even in an isolated molecule, although not all phase information is lost, via a theoretical study of a central electron spin qubit interacting with nearby nuclear spins in prototypical magnetic molecules. The residual coherence, which is molecule-dependent, provides a microscopic rationalization for the nuclear spin diffusion barrier proposed to explain experiments. The contribution of nearby molecules to the decoherence has a nontrivial dependence on separation, peaking at intermediate distances. Molecules that are far away affect only the long-time behavior. Because the residual coherence is simple to calculate and correlates well with the coherence time, it can be used as a descriptor for coherence in magnetic molecules. This work will help establish design principles for enhancing coherence in molecular spin qubits and serve to motivate further theoretical work.