Experimental Investigation Of Quantum Correlations And Bohmian Trajectories

The quantum correlations,for example EPR steering and quantum contextulity,draw an important distinction between quantum mechanics and the world as described by classical mechanics.EPR steering describes the ability of one party to remotely affect another's state through local measurements.One of the most distinguishable properties of EPR steering is its asymmetric aspect,which is different from the symmetry concepts of entanglement and Bell nonlocality.And the quantum contextuality means that the outcomes of measurements,in a system no less than three dimensions,are depending on the context in which they are measured.Even the single particle system can exhibit quantum contextuality,and the verification process of quantum contextuality can be independent of the initial state.As a kind of quantum resources,they have an important role in various quantum information tasks,and have received more and more attention.Quantum steering and quantum contextuality are all belong to the foundational concepts in quantum theory.It is helpful for us to get a profound understanding of quantum correlation to study the EPR steering and quantum contextuality.On the one hand,it has an important theoretical value:it can further enrich the content of quantum theory and deepen peoplc's understanding of the nature of quantum phenomena.On the other hand,it also has an important application value:it can help us make better use of these quantum resources to perform quantum information tasks.Although quantum mechanics have achieved great success in many fields since its establishment,the physical world described by quantum theory is probabilistic and indefinite,which is totally different from people's intuition and accustomed to feelings.However,the "guided wave" hidden variable theory developed by Bohm et al.which is an ontological interpretation of quantum mechanics.They interpretation of the quantum mechanical formalism with its model of particle plus "guiding" wave:a quantum system consists of a wave and a particle,the wave evolves according to Schrodingers equation and the particle according to a guidance condition that makes the particle motion to be dependent on the wave evolution.Thus,in contrast to the Copenhagen formulation,the Bohmian formulation allows for an easy visualization of quantum phenomena in terms of trajectories that has important demystifying or clarifying consequences.During my PhD,I mainly carried out some experimental researches on the basic problems of quantum information such as one-way EPR steering,quantum contextuality and Bohmian trajectories:1.Demonstration of multisetting one-way Einstein-Podolsky-Rosen steering in two-qubit systemsEinstein-Podolsky-Rosen(EPR)steering,also called as quantum steering,stands between quantum entanglement and Bell nonlocality in the hierarchy,and possesses the asymmetric feature which may provide potential applications for the one-sided device-independent quantum key distribution.In this work,the steerability is quantified by the steering radius,which represents a necessary and sufficient steering criterion.The demonstrated one-way steering in the simplest bipartite quantum system is of funda-mental interest and may provide potential applications in one-way quantum information tasks.2.Experimental investigation of quantum contextualityContextuality is the critical resource behind fault-tolerant universal quantum com-putation,and its experimental research is an important subject in the field of quantum information.Moreover,contextuality offers a distinctive perspective on the striking properties of the quantum world by pointing out scenarios in which notions such as preparations and states play no role.The contextual correlations are demonstrated on quantum three-dimensional states encoded in the spatial modes of single photons gen-erated from a defect in a bulk silicon carbide.We have observed for the first time the optimal form of quantum state-independent contextuality respecting the condition of no-signaling between the measurements in the same context,which is essential to make sense of any test of contextuality.Platonic graphs have good symmetry,which gives rise to the largest quantum-classical difference.Among these solids we refer particu-larly to the icosahedron to build the four-dimension quantum contextuality experiment.Our quantum-correlation experiment sheds a new light on the conflict between quantum and classical physics.Our results reflect that different graphs have different power to demonstrate contextual correlations,which open a way for exploring quantum proper-ties with graphs as a start point and indicate that graph theory as it stands more physics than precedented thoughts.3.Experimental nonlocal steering of Bohmian trajectoriesThe concept of quantum trajectories in Bohmain mechanics allows us to under-stand the motion of microscopic particle in a similar way to the description of particles by Newtonian mechanics,which can be constructed using the technique of weak mea-surements.In our work,we further developed a method to reconstruct the Bohmain tra-jectory of entangled photons.We have experimentally demonstrated non-local steering of Bohmian trajectories.The results show a distinct signature of the non-local nature of BM,by showing the superluminal impact on the velocity of a particle,mediated by the quantum potential,or pilot wave.The phenomenon we observe also yields an intuitive picture of the steering:changing the path of a particle from a distance.4.Observing Bohmian momentum transfer in double-slit "which-way" mea-surementsThe single-particle Young's double-slit experiment is the quintessential example of the wave-particle duality of quantum mechanics.Making a "which-way" measurement(WWM)to identify which slit a particle goes through in a double-slit apparatus will reduce the visibility of interference fringes.In this work,we used the Bohmian proba-bility distribution to experimentally quantify the momentum transfer,which is observed to be not a momentum kick that occurs at the point of the WWM,but nonclassically accumulate during the propagation of the photons.We further confirm a quantitative relation between the loss of visibility consequent on a WWM and the late-time momen-tum transfer.The results of our work give an intuitive picture thataids understanding of wave-particle duality and complementarity.