Quantum Circuit Resizing via Serial Execution

Quantum systems with limited physical qubits cannot execute quantum circuits with more logical qubits than physically-available ones, leading to compile-time errors. As it is unrealistic to expect quantum systems to provide sufficient qubits in the near future, there is a pressing need to explore strategies to execute large circuits on small systems, as current systems are comparatively small in comparison to the needs of the existing and emerging quantum algorithms/circuits. In this work, we analyze quantum programs to identify qubits that can be reused mid-program to execute the circuit with fewer qubits; this process is termed as resizing or serialization. Based on our analysis, we then propose a compiler-driven approach that selects the most beneficial qubits for circuit resizing, and provide proof of work for the algorithm. The results with our proposed circuit resizing indicate that it can i) execute large circuits that cannot originally fit into small number of physical qubits in current quantum systems, ii) significantly improve PST (Probability of Successful Trial) by 2.1X, and iii) and 53% reduction in circuit execution time when both the original and our serialized programs can fit into the target quantum hardware.