Modular construction of special mixed quantum states

  • M. MichelEmail author
  • G. Mahler


For a homogeneous quantum network of N subsystems with n levels each we consider separable generalized Werner states. A generalized Werner state is defined as a mixture of the totally mixed state and an arbitrary pure state \(\vert\psi\rangle\): \(\hat{p}_{Werner} = (1-\epsilon)\hat{1}+\epsilon\vert\psi\rangle\langle\psi\vert\) with a mixture coefficient \(\epsilon\). For this density operator \(\hat{p}_{Werner}\) to be separable, \(\epsilon\) will have an upper bound \(\epsilon_{sep}\leq1\). Below this bound one should alternatively be able to reproduce \(\hat{p}_{Werner}\) by a mixture of entirely separable input-states. For this purpose we introduce a set of modules, each contributing elementary coherence properties with respect to a generalized coherence vector. Based on these there exists a general step-by-step mixing process for any \(\epsilon_{mix}\leq\epsilon_{max}\). For \(\vert\psi\rangle\) being a cat-state it is possible to define an optimal process, which produces states right up to the separability boundary ( \(\epsilon_{max} = \epsilon_{sep} \)).


Coherence Optimal Process Quantum State Mixed State Pure State 
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© Springer-Verlag Berlin/Heidelberg 2003

Authors and Affiliations

  1. 1.Institute of Theoretical Physics IUniversity of StuttgartStuttgartGermany

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