QuCloud: A New Qubit Mapping Mechanism for Multi-programming Quantum Computing in Cloud Environment

For a specific quantum chip, multi-programming improves overall throughput and resource utilization. Previous studies on mapping multiple programs often lead to resource under-utilization, high error rate, and low fidelity. This paper proposes QuCloud, a new approach for mapping quantum programs in the cloud environment. We have three new designs in QuCloud. (1) We leverage the community detection technique to partition physical qubits among concurrent quantum programs, avoiding the waste of robust resources. (2) We design X-SWAP scheme that enables inter-program SWAPs and prioritizes SWAPs associated with critical gates to reduce the SWAP overheads. (3) We propose a compilation task scheduler that schedules concurrent quantum programs to be compiled and executed based on estimated fidelity for the best practice. We evaluate our work on publicly available quantum computer IBMQ16 and a simulated quantum chip IBMQ50. Our work outperforms the state-of-the-art work for multi-programming on fidelity and compilation overheads by 9.7% and 11.6%, respectively.