Low-Depth Unitary Coupled Cluster Theory for Quantum Computation
Low-Depth Unitary Coupled Cluster Theory for Quantum Computation
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DOI：
10.1021/acs.jctc.1c01026
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发表时间：
2022-04-12
影响因子：
5.5
通讯作者：
Freericks, J. K.
中科院分区：
文献类型：
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作者：
Chen, Jia;Cheng, Hai-Ping;Freericks, J. K.
酉耦合簇 (UCC) 近似是通过变分量子本征解算器算法在量子计算机上进行电子结构计算的最有前途的波函数分析之一。然而，对于具有多个轨道的大型系统，所需数量的 UCC 因子仍然会导致非常深的量子电路，这可能难以实现。基于对弱相关和强相关分子的大多数 UCC 振幅都很小的观察，我们设计了一种算法，在小振幅中采用泰勒展开，用额外的测量来权衡电路深度。通过对一小组经过精确处理的 UCC 因子进行扩展，可以考虑强相关性。接近平衡时，泰勒级数展开通常效果很好，不需要包含任何精确的因子；随着分子被拉伸和相关性增加，我们发现只有少数因素需要精确处理
The unitary coupled cluster (UCC) approximation is one of the more promising wave function ansa''tzes for electronic structure calculations on quantum computers via the variational quantum eigensolver algorithm. However, for large systems with many orbitals, the required number of UCC factors still leads to very deep quantumcircuits, which can be challenging to implement. Based on the observation that mostUCC amplitudes are small for both weakly correlated and strongly correlated molecules,we devise an algorithm that employs a Taylor expansion in the small amplitudes, tradingoffcircuit depth for extra measurements. Strong correlations can be taken into account by performing the expansion about a small set of UCC factors, which are treated exactly. Near equilibrium, the Taylor series expansion often works well without the need to include any exact factors; as the molecule is stretched and correlations increase, we find only a small number of factors need to be treated exactly