The Studies On Nonlocal Advantage Of Quantum Coherence

Quantum coherence arising from the superposition principle of quantum states,like quantum entanglement,is considered a useful resource in quantum information theory.Now,quantun coherence has been widely used in many fields,such as quantum biology,quantum information science,quantum thermodynamics and so on.The study of quantum coherence can not only expand the theory of quantum mechanics and deepen the understanding o_f the nature of quantum physics,but also promote the application of quantum resources in quantum information processing.Quantum steering which is introduced by Schrodinger in 1935 to analyze the EPR-paradox is another important resource.Recently,more and more studies have focused on the relationsh ip between quantum coherence and quantum steering.Based on the study of the relationship between the two resources,some scholars have proposed new concepts,such as the concept of quantum coherence of steered states and the definition of nonlocal advantage of quantum coherence.It is well known that quantum mechanics and the relativity theory are two important components of modern physics.The real world is a strictly non-inertial system,and there will always exist rotation and acceleration,so we need to take into account the effects of relativity.Therefore,the study of quantum resource theory under the framework of relativity has a very positive role in promoting the understanding of quantum mechanics,relativity and quantum information theory.On the other hand,because the quantum system is actually open,there must exist an interaction between the quantum system and the surrounding environment in the actual quantum task.Thus,the decoherence effect will be generated.Therefore,it is very important to overcome the quantum decoherence and suppress the influence of noise environment on the quantum coherence in the open quantum system(noise channel).This will be of great significance to the application of quantum coherence.In this paper,we mainly study the dynamic behavior of nonlocal advantages of quantum coherence and quantum coherence in the background of non-inertial system.In addition,four protection schemes of quantum coherence based on quantum weak measurement and measurement reversal in amplitude damping channel are proposed.The main research results are as follows:1· Nonlocal advantage of quantum coherence under relativistic frame.We investigate the influence of the Unruh effect on the achievement of nonlocal advantage of quantum coherence for two entangled Unruh-Dewitt detectors system when one of them is accelerated and interacted with a massless scalar field.In addition,we study the dynamics of quantum coherence,Bell nonlocality,steering,entanglement and quantum discord under Unruh thermal noise.The results show that:(1)nonlocal advantage of quantum coherence decreases monotonically with the increase of acceleration and suffers from a"sudden death",which indicates that such a nonlocal advantage cannot be obtained when the acceleration exceeds a certain value.(2)Furthermore,it is interesting that we found the steering-Bell nonlocality-nonlocal advantage of quantum coherence hierarchy.(3)Comparing the above quantum resources,we found that the"sudden death"behavior for the relative entropy of coherence and quantum discord do not take place.These results will help us understand and apply the nonlocal advantages of quantum coherence under relativistic effects.It require us to seek some measures to enhance its robustness.2.Protecting quantum coherence in an open system under non-inertial frames-Based on the weak measurement,we propose four strategies to protect the quantum coherence of two-bit Dirac systems under the non-inertial system.The results show that:(1)Weak measurement can indeed be used to protect quantum coherence in amplitude damping channel under non-inertial frames.(2)In scheme 3 and 4,with the increase of weak measurement intensity,the better the protection effect,the lower the success probability.(3)There are some special phenomena in the first two schemes.As the increases of weak measure strength,quantum coherence of the system cannot be improved,which is determined by the properties of weak measure.(4)In practice,we want to achieve the best effect of protection must taking into account noise channel parameters and weak measurement intensity.