Efficient Scheme For Creating A W-type Of Entangled Coherent State In Multi-microwave Cavities Without Measurement

W-type entangled coherent states have important applications in quantum communication.Previous works require performing measurement in the preparation of such W states.We here propose an efficient scheme for creating a W-type entangled coherent state of three microwave cavities without need of measurement.This scheme is based on a circuit-QED setup,which consists of three microwave cavities coupled to a threelevel superconducting flux qubit.Because no measurement is required,the W state can be generated deterministically.In addition,the circuit complexity is greatly reduced because of using only one qutrit to couple the three cavities.Numerical simulations show that high-fidelity production of this W state is feasible with current circuit QED technology.This scheme is universal and can be extended to create the W-type entangled coherent state in a system consisting of three microwave or optical cavities coupled to a three-level natural or artificial atom.This paper is organized as follows.In chapter 1,we introduce the research background,research content and significance.In chapter 2,a brief introduction of superconducting qubit is presented.In chapter 3,some basic theory is introduced.In chapter 4,we show how to prepare the W-type optical entangled coherent state.In chapter 5,we present investigation on the experimental feasibility.In chapter 6,a brief summary is presented.