In quantum computing, research and development of devices, architecture, optimization techniques, algorithms, and applications are evolving with eagerness in parallel. To make these work mutually beneficial, practical and accurate quantum computer simulators as system-wide design frameworks are necessary. In this paper, we focus on measurement and initialization errors of qubits. These errors are inevitable because these procedures are interfaces between classical and quantum information processing. We model the quantum non-demolition detection technique as measurement and initialization methods and implement them on Intel-QS, a high-performance quantum simulator. Our case study with quantum Fourier transform on 8 qubits configuration demonstrates the importance of taking these errors into account. That is, post-selection, which improves the initialization fidelity, can enlarge the gap between the theoretical result and incorrect outputs by 3.35 times.