  Real-time control software and hardware is essential for operating quantum
computers. In particular, the software plays a crucial role in bridging the gap
between quantum programs and the quantum system. Unfortunately, current control
software is often optimized for a specific system at the cost of flexibility
and portability. We propose a systematic design strategy for modular real-time
quantum control software and demonstrate that modular control software can
reduce the execution time overhead of kernels by 63.3% on average while not
increasing the binary size. Our analysis shows that modular control software
for two distinctly different systems can share between 49.8% and 91.0% of
covered code statements. To demonstrate the modularity and portability of our
software architecture, we run a portable randomized benchmarking experiment on
two different ion-trap quantum systems.
