Here we present qFlex, a flexible tensor network-based quantum circuit simulator. qFlex can compute both the exact amplitudes, essential for the verification of the quantum hardware, as well as low-fidelity amplitudes, to mimic sampling from Noisy Intermediate-Scale Quantum (NISQ) devices. In this work, we focus on random quantum circuits (RQCs) in the range of sizes expected for supremacy experiments. Fidelity f simulations are performed at a cost that is 1/f lower than perfect fidelity ones. We also present a technique to eliminate the overhead introduced by rejection sampling in most tensor network approaches. We benchmark the simulation of square lattices and Google’s Bristlecone QPU. Our analysis is supported by extensive simulations on NASA HPC clusters Pleiades and Electra. For our most computationally demanding simulation, the two clusters combined reached a peak of 20 Peta Floating Point Operations per Second (PFLOPS) (single precision), i.e., 64% of their maximum achievable performance, which represents the largest numerical computation in terms of sustained FLOPs and the number of nodes utilized ever run on NASA HPC clusters. Finally, we introduce a novel multithreaded, cache-efficient tensor index permutation algorithm of general application.

在这里，我们介绍基于弹性张量网络的量子电路模拟器qFlex。qFlex可以计算对于验证量子硬件必不可少的精确幅度，以及低保真幅度，以模拟从有噪声的中级量子（NISQ）设备进行的采样。在这项工作中，我们专注于至高无上实验预期的大小范围内的随机量子电路（RQC）。逼真度f仿真的执行成本为1 / f低于完美的保真度。我们还提出了一种消除大多数张量网络方法中拒绝采样所带来的开销的技术。我们以正方形格子和Google Bristlecone QPU的模拟为基准。我们的分析得到了NASA HPC集群Pleiades和Electra的广泛模拟的支持。对于我们最需要计算的模拟，两个群集的组合达到了每秒20 Peta浮点运算（PFLOPS）（单精度）的峰值，即达到其最大可实现性能的64％，这代表了在持续时间方面最大的数值计算FLOP和所利用的节点数曾经在NASA HPC集群上运行。最后，我们介绍了一种新颖的多线程，高效缓存的张量索引置换算法。