Spacetime curvature of the Earth deforms wave packets of photons sent from the Earth to satellites, thus influencing the quantum state of light. We show that Gaussian steering of photon pairs, which are initially prepared in a two‐mode squeezed state, is affected by the curved spacetime background of the Earth. We demonstrate that quantum steerability of the state increases for a specific range of height h and then gradually approaches a finite value with further increasing height of the satellite's orbit. Comparing with the peak frequency parameter, the Gaussian steering changes more for different squeezing parameters, while the gravitational frequency effect leads to quantum steering asymmetry between the photon pairs. In addition, we find that the influence of spacetime curvature on the steering in the Kerr spacetime is very different from the non‐rotating case because special relativistic effects are involved.

We study the dynamics of steering between two correlated Unruh-Dewitt detectors when one of them locally interacts with external scalar field via different quantifiers. We find that the quantum steering, either measured by the entropic steering inequality or the Cavalcanti-Jones-Wiseman-Reid inequality, is fragile under the influence of Unruh thermal noise. The quantum steering is found always asymmetric and the asymmetry is extremely sensitive to the initial state parameter. In addition, the steering-type quantum correlations experience "sudden death" for some accelerations, which are quite different from the behaviors of other quantum correlations in the same system. It is worth noting that the domination value of the tight quantum steering exists a transformation point with increasing acceleration. We also find that the robustness of quantum steerability under the Unruh thermal noise can be realized by choosing the smallest energy gap in the detectors.

Based on the strongly lensed gravitational waves (GWs) from compact binary coalescence, we propose a new strategy to examine the fluid shear viscosity of dark matter (DM) in the GW domain, i.e. whether a GW experiences the damping effect when it propagates in DM fluid with nonzero shear viscosity. By assuming that the DM self-scatterings are efficient enough for the hydrodynamic description to be valid, our results demonstrate that future ground-based Einstein Telescope and satellite GW observatory (big bang observer) may succeed in detecting any DM self-interactions at the scales of galaxies and clusters.

In this paper, we carry out an assessment of cosmic distance duality relation (CDDR) based on the latest observations of HII galaxies acting as standard candles and ultra-compact structure in radio quasars acting as standard rulers. Particularly, two machine learning reconstruction methods [Gaussian Process (GP) and Artificial Neural Network (ANN)] are applied to reconstruct the Hubble diagrams from observational data. We show that both approaches are capable of reconstructing the current constraints on possible deviations from the CDDR in the redshift range $$z\sim 2.3$$ z ∼ 2.3 . Considering four different parametric methods of CDDR, which quantify deviations from the CDDR and the standard cosmological model, we compare the results of the two different machine learning approaches. It is observed that the validity of CDDR is in well agreement with the current observational data within $$1\sigma $$ 1 σ based on the reconstructed distances through GP in the overlapping redshift domain. Moreover, we find that ultra-compact radio quasars could provide $$10^{-3}$$ 10 - 3 -level constraints on the violation parameter at high redshifts, when combined with the observations of HII galaxies. In the framework of ANN, one could derive robust constraints on the violation parameter at a precision of $$10^{-2}$$ 10 - 2 , with the validity of such distance duality relation within $$2\sigma $$ 2 σ confidence level.