Multi-programming mechanism on near-term quantum computing

As near-term quantum hardware has several physical limitations and unavoidable noisy quantum operations, only small circuits with shallow depths can be executed with reliable results. This leads to the quantum hardware under-utilization issue. With the growing demand to access quantum chips and limited hardware cloud service, how to utilize the quantum hardware more efficiently while maintaining the output state fidelity is becoming a timely issue. In this chapter, we introduce the multi-programming mechanism to enable parallel circuit executions on NISQ computers. One severe issue caused by the multi-programming mechanism is crosstalk, due to the growing number of simultaneous quantum operations. We first analyze the impact of crosstalk on output state fidelity when applying multi-programming mechanism. Second, we propose a Quantum Multi-programming Compiler (QuMC), which takes the hardware topology, calibration data, and crosstalk into account, to execute multiple quantum circuits simultaneously with reliability. Third, we improve our QuMC approach and present the Quantum Crosstalk-aware Parallel circuit execution (QuCP) method, which enables parallel circuit executions without the overhead of crosstalk characterization. Finally, we discuss the applications of multi-programming mechanism for NISQ computing.