  Superconducting coupler architecture demonstrates great potential for
scalable and high-performance quantum processors, yet how to design efficiently
and automatically 'Qubit-Coupler-Qubit (QCQ)' of high performance from the
layout perspective remains obscure. In this work, this issue is studied for the
first time resulting in three key findings. Firstly, we acquire the crucial
zero-coupling condition that is only dependent on the geometric design of the
layout. Secondly, the upper bound of the qubit-qubit effective coupling is
found as $0.0822~ \omega_l/\beta_s^2$ which surprisingly depends only on the
artificially pre-decided quantities $\omega_l, \beta_s$ instead of specific
layouts. Thirdly, we propose an optimal layout design procedure to reach the
very upper bound, leading to efficient and high-performance layout design. The
effectiveness of the procedure has been demonstrated scrupulously using
electromagnetic simulation experiments. As a stirring application, we report a
state-of-the-art 3202 um long-range and scalable QCQ layout that is especially
crucial to quantum error correction. Our work provides practical guides to
optimize the performance of the existing coupler architecture, find out novel
layouts, and further advance the progress of quantum chip design automation.
