Superbroadcasting of continuous variable mixed states
Giacomo Mauro D’Ariano, Paolo Perinotti, Massimiliano Federico Sacchi · New Journal of Physics · 2006
We consider the problem of broadcasting quantum information encoded in the average value of the field from N to M>N copies of mixed states of radiation modes. We derive the broadcasting map that preserves the complex amplitude, while optimally reducing the noise in conjugate quadratures. We find that from two input copies broadcasting is feasible, with the possibility of simultaneous purification (superbroadcasting). We prove similar results for purification (M<=N) and for phase-conjugate broadcasting.