Abstract: Grover algorithm is a quantum search algorithm that can find the target state efficiently. However, with the increase of the amount of searching data, Grovers quantum circuit is faced with the complex gate decomposition problem. In todays NISQ era, resources are very limited, so circuit depth 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 2P-Grover algorithm. The simulation experiment was carried out on the quantum computing framework Cirq.  The experimental results show that, compared with Grover algorithm, the 2P-Grover algorithm can reduce the circuit depth by at least 1.2 times and maintain a high probability of search success.

Key words: quantum circuit, Grover algorithm, QPSA algorithm, quantum information, Cirq framework