### Abstract

Decoherence is believed to deteriorate the ability of a purification scheme that is based on the idea of driving a system to a pure state by repeatedly measuring another system in interaction with the former and hinder for a pure state to be extracted asymptotically. Nevertheless, we find a way out of this difficulty by deriving an analytic expression of the reduced density matrix for a two-qubit system immersed in a bath. It is shown that we can still extract a pure state if the environment brings about only dephasing effects. In addition, for a dissipative environment, there is a possibility of obtaining a dominant pure state when we perform a finite number of measurements.

Original language | English |
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Pages (from-to) | 042114-1-042114-12 |

Number of pages | 12 |

Journal | PHYSICAL REVIEW A |

Volume | 77 |

Publication status | Published - 2008 |

### All Science Journal Classification (ASJC) codes

- Atomic and Molecular Physics, and Optics

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## Cite this

Militello, B., Messina, A., Yuasa, & Nakazato (2008). Estimation of the repeatedly projected reduced density matrix under decoherence.

*PHYSICAL REVIEW A*,*77*, 042114-1-042114-12.