  As we venture into the Intermediate-Scale Quantum (ISQ) era, the proficiency
of modular arithmetic operations becomes pivotal for advancing quantum
cryptographic algorithms. This study presents an array of quantum circuits,
each precision-engineered for modular arithmetic functions critical to
cryptographic applications. Central to our exposition are quantum modular
adders, multipliers, and exponential operators, whose designs are rigorously
optimized for ISQ devices. We provide a theoretical framework and practical
implementations in the PennyLane quantum software, bridging the gap between
conceptual and applied quantum computing. Our simulations validate the efficacy
of these methodologies, offering a strategic compass for developing quantum
algorithms that align with the rapid progression of quantum technology.
