  We analyze the experimental error budget of parametric resonance gates in a
tunable coupler architecture. We identify and characterize various sources of
errors, including incoherent, leakage, amplitude, and phase errors. By varying
the two-qubit gate time, we explore the dynamics of these errors and their
impact on the gate fidelity. To accurately capture the impact of incoherent
errors on gate fidelity, we measure the coherence times of qubits under gate
operating conditions. Our findings reveal that the incoherent errors, mainly
arising from qubit relaxation and dephasing due to white noise, limit the
fidelity of the two-qubit gates. Moreover, we demonstrate that leakage to
noncomputational states is the second largest contributor to the two-qubit
gates infidelity, as characterized using leakage-randomized benchmarking. The
error budgeting methodology we developed here can be effectively applied to
other types of gate implementations.
