The protection of entanglement and fidelity of cluster states under amplitude damping decoherence by means of weak measurement is investigated. Employing the prior weak measurement and post weak measurement reversal, the decoherence of system can be prohibited effectively, and the fidelity is improved obviously. Besides, the evolution of entanglement and fidelity are dependent on the weak measurement strength P. By choosing some proper values of P, the entanglement and fidelity can be protected optimally.
Recently Song et al., Phys. Rev. A 80, 012331 (2009), have discovered that certain two-qutrit entangled states interacting with multi-local decoherence undergo distillability sudden death whereas their locally equivalent states do not exhibit such behavior. We have found that their basic equation of motion missed some terms and therefore the subsequent calculations and conclusions are not correct/valid except that distillability sudden death may occur. We provide the missing terms and point out the corrections which must be done in the literature to remove confusion. Moreover, we have studied this feature for certain entangled states under global, collective and multi-local decoherence. We have found that entanglement sudden death and distillability sudden death may happen under global and multi-local noises. Moreover, local unitary transformations can not avoid distillability sudden death.
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