  Currently available quantum computers are prone to errors. Circuit
optimization and error mitigation methods are needed to design quantum circuits
to achieve better fidelity when executed on NISQ hardware. Dynamical decoupling
(DD) is generally used to suppress the decoherence error and different DD
strategies have been proposed. Moreover, the circuit fidelity can be improved
by pulse-level optimization, such as creating hardware-native pulse-efficient
gates. This paper implements all the popular DD sequences and evaluates their
performances on IBM quantum chips with different characteristics for various
well-known quantum applications. Also, we investigate combining DD with
pulse-level optimization method and apply them to QAOA to solve Max-Cut
problem. Based on the experimental results, we found that DD can be a benefit
for only certain types of quantum algorithms, while the combination of DD and
pulse-level optimization methods always has a positive impact. Finally, we
provide several guidelines for users to learn how to use these noise mitigation
methods to build circuits for quantum applications with high fidelity on IBM
quantum computers.
