Noncommuting mixed states cannot be broadcast
arXiv:quant-ph/9511010 · doi:10.1103/PhysRevLett.76.2818
Abstract
We show that, given a general mixed state for a quantum system, there are no physical means for {\it broadcasting\/} that state onto two separate quantum systems, even when the state need only be reproduced marginally on the separate systems. This result generalizes and extends the standard no-cloning theorem for pure states.
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