Fig. 2: Cross-correlation of sensor network.
From: Long-baseline quantum sensor network as dark matter haloscope
a Diagram of the cross-correlation between the atomic magnetometers located in station A (Suzhou) and station B (Harbin). The blue dots and red dots represent the cross-correlation from the magnetometers in the same station and different stations, respectively. b Two-dimensional cross-correlation spectrum of two sensors. c, d The network sensitivity as a function of correlators number \({{{{{{{\mathcal{N}}}}}}}}\). As an example, The magnetic sensitivity of network at 10.1 Hz increases with increasing correlators number and can be fitted with the function of \({{{{{{{{\mathcal{N}}}}}}}}}^{-a}\) (a ≈ 0.25). Distribution of the signal-to-noise ratio (SNR) of the cross-correlation spectrum between two sensors: e two sensors in Suzhou station; f two sensors in Harbin; g one sensor in Suzhou station and the other in Harbin station. The SNR distributions in e and f are asymmetrical due to the common-mode magnetic noise (≈5 fT/Hz1/2) of the shield room that only contributes to the positive part of the SNR. In contrast, the SNR distribution of two sensors from different stations is symmetrical without common-mode noise.
