Traveling-wave parametric amplifier–induced qubit dephasing: analysis and mitigation

The mitigation of dephasing poses a significant challenge to improving the performance of error-prone superconducting quantum computing systems. Here, the dephasing of a transmon qubit in a dispersive readout regime was investigated by adopting a Josephson traveling-wave parametric amplifier as the preamplifier. Our findings reveal that the potent pump leakage from the preamplifier may lead to severe dephasing. This could be attributed to a mixture of measurement-induced dephasing, ac Stark effect, and heating. It is showed that pulse-mode readout is a promising measurement scheme to mitigate qubit dephasing while minimizing the need for bulky circulators. Our work provides key insights into mitigating decoherence from microwave-pumped preamplifiers, which will be critical for advancing large-scale quantum computers.