Improving cutoff frequency estimation via optimized π-pulse sequence

• Published in: Chinese physics B Vol. 34; no. 1; pp. 10309 - 10314
• Main Authors: Zheng, Wang-Sheng, Zhang, Chen-Xia, Gong, Bei-Li
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.01.2025
• Subjects: environment parameters estimation; optimized; pulse sequence; quantum Fisher information
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/ad9ba1

The cutoff frequency is one of the crucial parameters that characterize the environment. In this paper, we estimate the cutoff frequency of the Ohmic spectral density by applying the π -pulse sequences (both equidistant and optimized) to a quantum probe coupled to a bosonic environment. To demonstrate the precision of cutoff frequency estimation, we theoretically derive the quantum Fisher information (QFI) and quantum signal-to-noise ratio (QSNR) across sub-Ohmic, Ohmic, and super-Ohmic environments, and investigate their behaviors through numerical examples. The results indicate that, compared to the equidistant π -pulse sequence, the optimized π -pulse sequence significantly shortens the time to reach maximum QFI while enhancing the precision of cutoff frequency estimation, particularly in deep sub-Ohmic and deep super-Ohmic environments.