论文标题

远程相互作用系统的变异量子模拟

Variational quantum simulation of long-range interacting systems

论文作者

Lyu, Chufan, Tang, Xiaoyu, Li, Junning, Xu, Xusheng, Yung, Man-Hong, Bayat, Abolfazl

论文摘要

当前的量子模拟器遭受了多种限制,例如相干时间,嘈杂的操作,错误的读数和某些平台上的量子连接限制。差异量子算法是近期量子模拟中最有前途的方法,可以实现与经典计算机相比的实用量子优势。在这里,我们探索具有不同级别的量子连接性的变异量子算法,用于对远程相互作用系统的基态以及自旋挤压状态的产生的数字模拟。我们发现,随着相互作用变得更加长,变化算法的效率降低,实现了较低的忠诚度并要求进行更多的优化迭代。特别是,当系统接近其关键时,效率甚至更低。即使量子和经典资源较少,远处量子位之间的连通性也可以改善结果。我们的结果表明,通过将电路层与不同级别的连通性混合可以明智地改善性能。有趣的是,层的顺序变得非常重要,并在电路开头的长距离连接分组以优于其他排列。相同的电路设计也可以用来变化产生自旋挤压状态,作为量子计量学的资源。

Current quantum simulators suffer from multiple limitations such as short coherence time, noisy operations, faulty readout and restricted qubit connectivity in some platforms. Variational quantum algorithms are the most promising approach in near-term quantum simulation to achieve practical quantum advantage over classical computers. Here, we explore variational quantum algorithms, with different levels of qubit connectivity, for digital simulation of the ground state of long-range interacting systems as well as generation of spin squeezed states. We find that as the interaction becomes more long-ranged, the variational algorithms become less efficient, achieving lower fidelity and demanding more optimization iterations. In particular, when the system is near its criticality the efficiency is even lower. Increasing the connectivity between distant qubits improves the results, even with less quantum and classical resources. Our results show that by mixing circuit layers with different levels of connectivity one can sensibly improve the performance. Interestingly, the order of layers becomes very important and grouping the layers with long-distance connectivity at the beginning of the circuit outperforms other permutations. The same design of circuits can also be used to variationally produce spin squeezed states, as a resource for quantum metrology.

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