论文标题
通过优化的信息完整的广义测量值来缓解Adapt-VQE的测量开销
Mitigating the measurement overhead of ADAPT-VQE with optimised informationally complete generalised measurements
论文作者
论文摘要
Adapt-VQE是一种可用于构造分子模拟的紧凑型Ansätze的鲁棒算法。它可以显着减少相对于其他方法(例如UCCSD)的电路深度,同时达到了更高的准确性,并且没有遭受所谓的贫瘠高原,这阻碍了许多硬件效率的Ansätze的各种优化。但是,在其标准实施中,它以梯度评估的形式引入了相当大的测量开销。在这项工作中,我们通过利用最近引入的能源评估方法来减轻此测量开销,该方法依赖于自适应信息完整的广义测量值(AIM)。除了提供一种有效的方法来测量能量本身外,还可以重复使用信息完成(IC)测量数据,以估计Adapt-VQE操作员池中操作员的所有换向器,仅使用经典的后处理。我们详细介绍了AIM-ADAPT-VQE计划,并通过几个H4 Hamiltonians和运营商池进行调查。我们的数值模拟表明,可以使用用于评估能量的测量数据可以重复使用以实施适应性VQE,而无需对此处考虑的系统进行其他测量开销。此外,我们表明,如果能量是在化学精确度中测量的,则最终电路中的CNOT数接近理想的电路。凭借稀缺的测量数据,AIM-ADAPT-VQE仍然以很高的可能性收敛到基态,尽管在某些情况下会增加电路深度。
ADAPT-VQE stands out as a robust algorithm for constructing compact ansätze for molecular simulation. It enables to significantly reduce the circuit depth with respect to other methods, such as UCCSD, while achieving higher accuracy and not suffering from so-called barren plateaus that hinder the variational optimisation of many hardware-efficient ansätze. In its standard implementation, however, it introduces a considerable measurement overhead in the form of gradient evaluations trough estimations of many commutator operators. In this work, we mitigate this measurement overhead by exploiting a recently introduced method for energy evaluation relying on Adaptive Informationally complete generalised Measurements (AIM). Besides offering an efficient way to measure the energy itself, Informationally Complete (IC) measurement data can be reused to estimate all the commutators of the operators in the operator pool of ADAPT-VQE, using only classically efficient post-processing. We present the AIM-ADAPT-VQE scheme in detail, and investigate its performance with several H4 Hamiltonians and operator pools. Our numerical simulations indicate that the measurement data obtained to evaluate the energy can be reused to implement ADAPT-VQE with no additional measurement overhead for the systems considered here. In addition, we show that, if the energy is measured within chemical precision, the CNOT count in the resulting circuits is close to the ideal one. With scarce measurement data, AIM-ADAPT-VQE still converges to the ground state with high probability, albeit with an increased circuit depth in some cases.