Research On Quantum Coherence And Quantum Illumination In Curved Spacetime

Relativistic quantum information is an interdisciplinary subject that combines quantum mechanics,relativity theory,quantum field theory and quantum information science.Relativistic quantum information mainly studies the following two aspects:(1)it explores the effects of acceleration and spacetime curvature on the preparation and transmission of quantum information over long distances,and provides feasible theory for the protection of quantum information under the framework of relativity;(2)it uses quantum resource to detect gravitational effect and spacetime structure,and provides theoretical support for gravitational wave detection and precise measurement of the gravitational constant.In this paper,quantum coherence and quantum illumination strategy under the framework of relativity has been studied:Firstly,we study the distribution and generation of quantum coherence of continuous variable systems in de Sitter space.Current studies have shown that there are some non-classical correlations between two causally disconnected regions in the exponentially accelerating de Sitter space.Therefore,it is of great significance to study the dissipation,freezing,growth and other behaviors of quantum coherence in the process of propagation in this spacetime background for the protection of quantum coherence.We find that the quantum coherence of the initial accessible quantum state decreases to a non-zero value with the increase of the spatial curvature effect,but in the case of massless scalar field and conformal coupled scalar field combined with infinite curvature limit,the quantum entanglement of the initial state decreases to zero.However,the quantum coherence between the causally disconnected regions arises with the increase of the space-time curvature effect.For the massless scalar field and the conformal coupled scalar field,the quantum coherence increases rapidly to a peak value when the infinite curvature limit is combined.Using these properties,we can theoretically make an effective space curvature detector.Secondly,quantum illumination strategy in curved spacetime is studied.Previous studies have shown that photons propagating in the spacetime background of the earth will be affected by the relativistic effect.Our main result is that the quantum illumination strategy under the influence of gravity uses less resources to achieve better detection results compared with classical optical detectors.The specific content is:(i)the detection error of quantum illumination strategy and single-mode coherent emitters in curved spacetime is lower than that in flat space-time,because gravity reduces the thermal signal brought back by the reflected signal from the target region.Besides,gravity reduces the amount of resources a probe consumes;(ii)compared with the single-mode coherent state emitter,the quantum illuminated emitter uses more sub-modes for spacetime detection,therefore the space-time detection error of the quantum illumination emitter is lower than that of the coherent state emitter.Our model can be applied to the development of microwave quantum illumination technology.Finally,we have made a simple summary and prospect.