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Bures volume of the set of mixed quantum states

Hans-Juergen Sommers·Karol Zyczkowski
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Abstract

We compute the volume of the N^2-1 dimensional set M_N of density matrices of size N with respect to the Bures measure and show that it is equal to that of a N^2-1 dimensional hyper-halfsphere of radius 1/2. For N=2 we obtain the volume of the Uhlmann 3-D hemisphere, embedded in R^4. We find also the area of the boundary of the set M_N and obtain analogous results for the smaller set of all real density matrices. An explicit formula for the Bures-Hall normalization constants is derived for an arbitrary N.

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Hans-Juergen Sommers, Karol Zyczkowski. 2005-02-17. Bures volume of the set of mixed quantum states. https://doi.org/10.1088/0305-4470/36/39/308

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