Study Of Quantum State Transfer In Circuit QED

Quantum information science is the interdisciplinary subject of quantum mechanics and information science,it is one of the hot spot of scientific research in recent years.Quantum information science includes quantum computation and quantum communication,who's basic unit is a quantum bit(qubit).Quantum coherence and entanglement can be used for quantum information processing,such as information coding,transmission,and calculation,etc.Circuit QED is considered to be one of the most promising candidates for implementing quantum information processing.Quantum state transfer plays an important role in quantum information processing.A qutrit has a larger Hilbert space than a qubit and can be used to encode more information.This paper mainly discusses how to transfer an arbitrary quantum state of single qutrit and N qutrits in circuit QED.In this paper,we first introduce the background and the motivation of research.As the foundation for our two theoretical research works,we introduce some knowledge of quantum information and circuit QED,which includes qubit and qutrit,superconducting qubit and resonator in circuit QED,and effective Hamiltonian,etc.Our first research scheme is information transfer of a qutrit in circuit QED.This scheme has the following advantages:(i)The setup is extremely simple.Only one cavity is required,thus no inter-cavity crosstalk needs to be considered.(ii)No photon is excited in the cavity,thus the cavity decoherence is greatly suppressed and high fidelities can be achieved by using a cavity with low quality factor.(iii)Neither classical pulse nor measurement is needed.Our second research scheme is transferring arbitrary states of N qutrits in circuit QED.This scheme has many advantages shown as follows:(i)only one cavity is required to implement N qutrits information transfer,there is no intercavity crosstalk to be considered;(ii)the cavity is mostly in the vacuum state during the transfer operations,photon decay in the cavity is greatly suppressed,so that a cavity with even a low quality factor can be used to achieve high-fidelity QST;(iii)any classical pulse,measurement,or other auxiliary system is not required so that operating errors can be reduced.We use numerical simulation to study the feasibility of the two schemes.Our numerical simulation shows that high-fidelity quantum state transfer can be achieved with state-of-the-art circuit quantum electrodynamics technology.