Noise analysis in correlated imaging, quantum and classical

Sammy Ragy, Gerardo Adesso

We investigate the nature of correlations in Gaussian light sources used for ghost imaging. We adopt methods from quantum information theory to distinguish genuinely quantum from classical correlations. Combining a microscopic analysis of speckle-speckle correlations with an effective coarse-grained description of the beams, we show that quantum correlations exist even in 'classical'-like thermal light sources, and appear relevant for the implementation of ghost imaging in the regime of low illumination. We further demonstrate that the total correlations in the thermal source beams effectively determine the quality of the imaging, as quantified by the signal-to-noise ratio.

A. Gatti, E. Brambilla

Xiangdong Li, LI Yuanyuan, Xinghui Liu +10 more

Correlation imaging based on entangled light sources offers potential benefits over classical single-photon imaging (SPI) in noisy environments, but also faces challenges such as low brightness, long integration times, and difficulty imaging biological organisms. Here, we propose noise-resistant biologically correlated biphoton imaging (CPI) based on a super-bunching light source, addressing the challenge of severe signal-to-noise ratio degradation in conventional SPI schemes. Our CPI, based on a super-bunching light source with high brightness, broadband spectrum (400–1100 nm), and strong quantum correlation (g 2 (0) ∼ 250), delivers high-performance, noise-resistant operation by extracting correlated photon pairs between the reference and signal paths. Experimental results show that under extreme noise conditions (noise-to-signal ratio up to 600), the structural profile in conventional SPI is entirely obscured by noise. In contrast, CPI still clearly resolves the target structure. Quantitative analysis further reveals that, as noise intensity increases, the imaging visibility of CPI can be enhanced by more than two orders of magnitude compared to SPI schemes. This study confirms the exceptional robustness and practical utility of super-bunching light-based correlated imaging in high-noise environments, offering an effective technical approach for high-quality biological observation in complex optical conditions.

Emma J. Pearce, Fazilah Nothlawala, Andrew Forbes +1 more

Yanfeng Bai, Shensheng Han

The theoretical analysis of quantum noise is presented in a correlated two-photon imaging system with entangled photons. The noise is strongly influenced by the size and the entanglement degree of the source. An increase of the source size results in a remarkable decrease of the amplitude of the noise when the size is much smaller than the aperture of the lens, whereas the change will not be obvious if the size is close to the aperture. The difference of the effects from the source between correlated imaging formed with entangled photons and with partially coherent light is also discussed.