Computing local invariants of qubit systems

  title={Computing local invariants of qubit systems},
  author={Markus Grassl and Martin R{\"o}tteler and Thomas Beth},
  journal={Physical Review A},
We investigate means to describe the nonlocal properties of quantum systems and to test if two quantum systems are locally equivalent. For this we consider quantum systems that consist of several subsystems, especially multiple quantum bits, i.e., systems consisting of subsystems of dimension 2. We compute invariant polynomials, i.e., polynomial functions of the entries of the density operator that are invariant under local unitary operations. As an example, we consider a system of two quantum… 

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