Fast and accurate quantum gates and measurements are essential for quantum computation within the limited coherence time of superconducting qubits. A quantum nondemolition (QND) readout is typically achieved through the dispersive interaction with a readout resonator. The reduction in the readout time required for qubit-state discrimination can be achieved through careful device designs, optimization of readout parameters, and the use of quantum-limited amplifiers. However, the transient response in the readout signal can degrade the readout fidelity, particularly during fast measurements. In this work, we propose enhancing readout fidelity and shortening readout time by systematically discarding the transient response. We numerically demonstrate that, with an optimal ratio between the dispersive shift and the photon decay rate, the effective readout time can be reduced by approximately $6\%\text{–}9\%$ for square pulses and $10\%\text{–}16\%$ for Gaussian pulses, while maintaining the same fidelity for the quantum efficiency $0.5\le \eta \le 1$.

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• Quantum engineering
• Superconducting qubits