  In this work we present two techniques that tremendously increase the
performance of tensor-network based quantum circuit simulations. The techniques
are implemented in the QTensor package and benchmarked using Quantum
Approximate Optimization Algorithm (QAOA) circuits. The techniques allowed us
to increase the depth and size of QAOA circuits that can be simulated. In
particular, we increased the QAOA depth from 2 to 5 and the size of a QAOA
circuit from 180 to 244 qubits. Moreover, we increased the speed of simulations
by up to 10 million times. Our work provides important insights into how
various techniques can dramatically speed up the simulations of circuits.
