Quantum Circuit Fragments: Efficient and verifiable format for quantum circuits

An efficient and intuitive format of quantum programs is an indispensable component to handle large-scale quantum computers. Representing and manipulating a sequence of quantum instructions as a network of quantum gates, i.e., quantum circuits, is one of the most successful approaches. Quantum circuits are intuitive since there are similar representations in classical engineering, such as electric or digital circuits. However, due to their differences from these classical circuits, naively automated manipulation and optimization for quantum circuit networks easily tend to an ill-defined format. To avoid this problem, a flexible and verifiable network format of quantum circuits is strongly demanded. In this extended poster abstract, we propose a representation with these properties, named quantum circuit fragments. In our representation, the connectivity of several types of wires in quantum circuits, qubit, control, and measurement-feedback wiring, are kept as three sets. We also provide a linear time algorithm to validate that our format can be converted to quantum circuits. Using our preliminary software to treat quantum circuit fragments, Q-Divide, we demonstrated that code complexity can be halved in practical cases. Thus, our work improves the efficiency of quantum computer development and motivates further exploration for efficient representation and manipulation of large-scale quantum programs.