Experimental Research On Quantum Measuremnt And Quantum Correlations Based On Linear Optics

Quantum information is the study of the information processing tasks that based on the quantum mechanical system.The basic unit of quantum information is the two-level quantum system,which commonly known as qubit.The ability to manipulate and readout the information of the single qubit is essential to implement the quantum infor-mation tasks and quantum computation.The information readout from a quantum sys-tem is done via a measurement.And the error-disturbance relations can serve as a merit of quantum measurement.When it comes to the multi-particle systems,the correlations between them is an important research area.They can act as the important resources in quantum information.For example,entanglement is an important resource in quantum information processing tasks,such as quantum teleportation,quantum error-correction,and quantum computing.One central question regarding entanglement is that in which way the quantum state may be entangled,it can help us to grasp the key features of each entanglement type.The non-locality is a resource to realize the device-independent quantum key distribution,simplify the communication complexity,it can also help us to understand the fundamental of quantum mechanics more deeply.Using the correlations between subsystem and the global system,we can develop an efficient method using linearly scaled local measurements and polynomially scaled post-processing times.By the analyses above,we conduct the following researches:1.We report an experimental implementation of a single-qubit generalized mea-surement scenario(POVM)based on a quantum walk model.We implement-ed the Trine POVM,SIC POVM and unambiguous discrimination of two non-orthogonal qubit states.2.We propose and implement an extendible method of quantum walk-based joint measurements of two noisy Pauli operators to test the error-disturbance relation for qubits introduced in[Phys.Rev.A 89,012129(2014)].Then,we formu-late and experimentally test a new universally valid state-dependent relation for three mutually unbiased observables.We therefore establish a fundamentally new method of testing error-disturbance.3.In our experiment,we prepare two four-qubit states with high fidelities and used the local filter technique to detect the entanglement types of them.Only local operations and local spectra are need in our method,which may shed light on the techniques of entanglement detection in more general way.4.I introduce the development of Bell nonlocality in linear optics.As an example,we experimental prepare a four-qubit Dicke state and test its nonlocality.How-ever,this type of experiments suffers from some loopholes.Then I describe these loopholes and the development of the loophole-free experiments.5.In such a set of states,whose correlations between neighboring particles are much more pronounced than correlations between distant systems,there exists an effi-cient method using linearly scaled local measurements and polynomially scaled post-processing times.In this study,we demonstrate the validity and the robust-ness of the reconstructed method for a four qubit state.