An efficient approach to precise quantum noise spectroscopy.

Quantum noise spectroscopy is a critical technique for characterizing noise responsible for decoherence in quantum systems, enabling extraction of the noise power spectral density, a key metric for understanding and mitigating environmental influences. However, theoretical models often assume ideal control pulses with instantaneous rise times. In any realistic experimental implementation, control pulses have finite rise times, and discounting this fact leads to errors in the reconstructed noise spectrum. Furthermore, our analysis demonstrates that control fields shift the peak of the filter function—-a tool for isolating frequencies of interest in the noise spectrum—away from the target frequency, reducing spectral sensitivity. We develop a fast, iterative algorithm to both account for realistic rise times and eliminate this deviation. Our findings highlight the importance of careful pulse engineering and theoretical understanding of physical limitations for accurate quantum noise spectroscopy in quantum computing platforms. The results have direct implications for the design of future characterization protocols that are necessary for the development of robust quantum technologies.