How long does it take to obtain a physical density matrix?
Lukas Knips, Christian Schwemmer, Nico Klein, Jonas Reuter, Géza Tóth, Harald Weinfurter · arXiv (Cornell University) · 2015
The statistical nature of measurements alone easily causes unphysical estimates in quantum state tomography. We show that multinomial or Poissonian noise results in eigenvalue distributions converging to the Wigner semicircle distribution for already a modest number of qubits. This enables to specify the number of measurements necessary to avoid unphysical solutions as well as a new approach to obtain physical estimates.