ar X iv : q ua nt - p h / 02 10 09 1 v 1 1 1 O ct 2 00 2 Note on Purifications of a Qubit
نویسندگان
چکیده
This note provides an explicit parametrization of all purifications of a mixed state in dimension 2 and all joint purifications, if any, of two mixed states in the same dimension. The former is parametrized by SO(3, R), while the latter is parametrized by SO(2, R), except when the state being purified is already pure. Using this, we show how to calculate certain measures of quantum information and as a byproduct we show how to solve one variation of the classical Procustes problem. This manuscript was originally scheduled to appear on the arXiv on October 8th, 2002, but it did not due to alleged illegibility of the pdf version of the manuscript.
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