Study Of Quantum Resource Based On Linear Optics

Quantum information is a hybird area of quantum mechanics and information the-ory.The basis of quantum information is to encode information on the quantum states,which we call qubit.The quantum correlation,such as entanglement and coherence,is the key that make some quantum tasks superior than its classical counterpart.Be-cause such correlation is important,the relevant resource theory of entanglement and coherence have been built.Among various quantum systems,linear optical system has great advantages in the study of properties of quantum systems.It is because photon has weak couplings with the environment and it has very long coherent time.Besides,experiment on linear optical system is operated in room temperature.Therefore,this thesis focuses on the detection and quantification of entanglement and coherence based on linear optical systems.Chapter Five to Seven are the main parts of this thesis.Chapter 5.Application of coherence:duality relation in multipath interfer-ometersAt the beginning,the wave property of photons is characterized by interference visibility,therefore,the theories and experiments for duality relation of photons focus only on two-path interferometers.After the establishment of resource theory of quantum coherence,researchers found that wave property of photons can also be characterized by coherence.Finally,duality relation for multi-path interferometers is formulated.In this chapter,we use a three-path Mach-Zehnder interferometer to verify a new tight duality relation,where we use l1-norm coherence measure to describe the wave property of photons.Chapter 6.Realization of measurement-device-independent and universal en-tanglement witnessEntanglement witness(EW)is designed to quickly detect entanglement in a quan-tum state without state tomography.However,there are two drawbacks of EW.One is state-dependent,and the other is measurement-device-dependent.The former limits the ability of EW to detect entanglement of unknown quantum states while the lat-ter limits the accuracy of the detection results.Therefore,we experimentally realize a measurement-device-independent and universal entanglement witness and demonstrate that it can be used as an entanglement measure.This new method solves both drawbacks of EW.Chapter 7.Computer-aided experimental techniquesWith the development of computer technology,computer has gradually entered into industrial production,life and other fields,greatly improving the control accuracy and production efficiency.At the same time,more and more electronic control de-vices are introduced into the quantum information experiment based on linear optical system,which lays a foundation for the introduction of computer technology into quan-tum information experiment.In this chapter,we introduce how we design and write a hardware-device control program to be used in the experiments in Chapter 5 and 6.The usage of the program is also introduced.