Stabilization Of All Bell States In A Lossy Coupled-cavity Array

As one of the main characteristics of quantum mechanics,entanglement has aroused a wide range of interests in various branches of physics,such as quantum computation,quantum communication and quantum phase transitions.However,the dissipation caused by the interaction between the quantum system and its environment is one of the remarkable obstacles to prepare entanglement in experiment.The dissipation results in the decoherent effect,which works against the interests of QIP tasks,and is inevitable at the actual situation.Fortunately,quantum dissipative schemes have been proposed theoretically,and implemented experimentally,which regards dissipation as a resource instead of resistant to it.It represents a dramatic breakthrough on quantum computation.However,the dissipation alone cannot guarantee a purely steady entangled state.Thus other means should be adopted to improve the purity of target state such as purification and feedback control.Based on a large number of theories and practices,we know that the Markovian feedback scheme based on continuous monitoring of quantum jumps is able to increase the steady-state entanglement in a model with two driven and collectively damped qubits.Since then,varieties of protocols take advantage of the combination of the quantum feedback and dissipation to generate high-fidelity entanglements.It is noteworthy that the fidelity of the entangled states in the schemes are distinctly affected by atomic spontaneous emission,and since atoms are placed at the same cavity,the local feedback control on a single atom becomes inconvenient.To overcome these problems,We propose a scheme to generate maximally entangled states based on continuous monitoring of quantum jumps.We set two ?-type atoms in an array of coupled cavities.The large-detuning limit is kept through the whole process,thus the excited levels of atoms are adiabatically eliminated,which suppresses the influence of spontaneous emission.Ultimately,the system can be stabilized in the target state and does not require precise control of the evolution time.Compared with the previous methods,our proposal can obtain all kinds of Bell states by changing the relative phase of the classical fields,and it is more convenient to manipulate atoms and more robust against atomic spontaneous emission.We make a comprehensive analysis of relevant parameters with current experimental parameters and confirm that the quantum-jump-based feedback is significantly useful to prepare entanglements with a high fidelity.