Preparation Of Entangled States In Circuit QED Systems

Quantum entanglement is an important physical property in quantum mechanics,which is widely used in quantum information and quantum computation.Entangled states,as carriers of information,are the basis of quantum information and quantum computing.They can be applied to quantum teleportation,quantum key distribution,quantum dense coding and so on.Therefore,how to prepare entangled states has become a subject of great physical significance.There are many preparation schemes based on different physical systems,such as non-linear optical system,ion trap system,cavity quantum electrodynamics system and so on.In this paper,In this paper,we prepare entangled states based on circuit quantum electrodynamics(QED).Circuit QED mainly studies the interaction between artificial atoms and microwave electromagnetic fields,and artificial atoms refer to superconducting quantum circuits.Superconducting quantum circuits based on Josephson junctions are non-harmonic and have discrete energy levels.The magnetic flux-qubit circuits with three Josephson junctions selected in the system in the paper.They are insensitive to flux noise and have great non-harmonic,which can maintain discrete energy levels in ultrastrong and deep-strong coupling regimes.The magnetic flux-qubit are coupled with LC circuit.Through frequency modulation and amplitude modulation of driving field,different Hamiltonian are obtained after choosing appropriate parameters.After time evolution,the multi-qubit W and multi-qubit GHZ states(Bell states of two qubit states)are prepared.In the first chapter,we briefly introduce the basic concepts such as qubits,quantum entanglement and so on,and show the schemes of entangled states preparation based on other systems and the application value of entanglement.In the second part,the circuit QED system is introduced,including three common qubit circuit with Josephson junctions and the coupling mechanism.In the main part of this paper,we introduce the physical model for quantum simulation.And we calculate the effective Hamiltonian.Multi-body W and GHZ states are prepared after parameter modulation.Finally,a summary of the full text is given.