Circuit optimization of Grover quantum search algorithm

Grover algorithm is a quantum search algorithm that can find the target state efficiently. However, with the increase in the amount of searching data, the circuit of Grover algorithm is faced with complex gate decomposition problem. In today's NISQ era, resources are very limited, so the depth of circuit is an important metric. This paper introduces a two-stage quantum search algorithm based on divide-and-conquer, which can run quickly in parallel on a quantum computer. A circuit optimization method is proposed to reduce the number of iterations by using block-level oracle circuit. Combining this method with divide-and-conquer idea, it is defined as the 2P-Grover algorithm. The simulation experiment was carried out on the quantum computing framework Cirq and compared with Grover algorithm. The experimental results show that the 2P-Grover algorithm can reduce the depth of circuit by at least 1.2 times and maintain a high probability of search success.