Research On The Model And Experiment Of Controlled Quantum Computing By Quantum Entanglement

Quantum computing is one of the most important development orientations for computer science in post Moore period.It works based on the principles of quantum mechanics,and using quantum effects,it dramatically reduces the time cost in some problems which are difficult for classical computing to solve.At present,studies on quantum computing mainly focus on its acceleration of computing power brought by quantum effects,it is still worth studying that whether quantum effects can bring abilities other than acceleration of computing power to quantum computing.The unique correlation in quantum entanglement is one of the quantum effects that do not exist in classical world.It enables measurement on one party’s qubit to affect the state of the other party’s qubit.This thesis studies the model of controlled quantum computing by quantum entanglement,and using this unique correlation we realize a special computing pattern,where one party’s quantum state and quantum operations are controlled by the other party.We further perform experimental verifications of our theoretical models.The results are significant for better understanding of quantum computing,building special quantum states,and exploring the special applications of distributed quantum computing.The contributions of this thesis include:1.We propose the model of controlled quantum computing by quantum entanglement,derive the experimental basis to realize it,and perform experimental verifications of the theoretical calculations.The proposed model is able to realize the control of the superposition among arbitrary quantum states and quantum operations.Aiming at the optical implementation of our model,we theoretically analyse the conditions to obtain entangled photons by spontaneous parametric down conversion with high qualities,and generate entangled photon pairs with high purity and brightness.The theoretical and experimental works in this part provide the technical support to the implementation of controlled quantum computing.2.We propose the model of remote-controlled quantum computing by quantum entanglement,and implement the model for single qubit.The proposed model is able to realize simultaneous control of the data and operation in quantum computing.We further provide a quantum circuit of this model.Using two photon’s polarization-path hyperentanglement,we design an implementation scheme of the computation on single qubit in this model,and experimentally verify the computation of six elementary single qubit quantum gates.The theoretical and experimental results in this part provide the technical method to the implementations of distributed quantum computing.3.We propose the model of quantum computing with controlled quantum oracle,and implement Grover’s algorithm in this model.We divide the circuit which is used to implement quantum algorithm dased on the quantum oracle into two parts,and separate these two parts spatially using quantum entanglement.We define these two parts as two devices to setting and solving the problem,respectively.This model enables the setter to simplify the quantum oracle according to the answer,while keeping the solver unaware of any information of the answer.It settles the problem that the quantum oracle is difficult to realize,and provides a new approach to experimentally demonstrate the advantage of quantum computing.Using two photon’s polarization-path hyperentanglement,we experimentally implement the computation of the Grover’s algorithm with four elements.The theoretical and experimental results in this part provide the technical method to the implementation of quantum algorithms based on quantum oracle.4.We propose the model of controlled superposition between wave state and particle state with a quantum multi-path beampslitter,and perform the experimental implementation of this model.We design an interferometer with a quantum multi-path beamsplitter,which is able to generate the entanglement between the photon and the quantum multipath beamsplitter in the interferometer,and in turn realize the control of the superposition between wave state and particle state in the wave-particle duality of the photon which are two special quantum states.We then study the wave-particle duality relation within this model.We design two experimental verification schemes using the polarization-path hybrid encoding and all-path encoding respectively,and perform the verification by the all-path encoding scheme.The theoretical and experimental results in this part indicate that,the the wave-particle duality relation with classical considerations is violated by the quantum superposition between wave state and particle state,and this effect is related with the interference between these two states.5.We propose the model of controlled superposition between wave state and particle state with a quantum which-path detector,and perform the experimental implementation of this model.Similar to the quantum multi-path beamsplitter,the controlled superposition between wave state and particle state is generated by the entanglement between the photon and the quantum which-path detector.We then study the wave-particle duality relation within this model.Using the polarization-path hybrid encoding,we experimentally realize the proposed model.The theoretical and experimental results in this part indicate that,the interference between these two states in this model can not violate the wave-particle duality relation between quantum coherence and path distinguishability,but it enables the observer to still obtain the photon’s entire path information,when the quantum which-path detector is partially present in the interferometer.