Quantum coding
Abstract
A theorem is proven for quantum information theory that is analogous to the noiseless coding theorem of classical information theory. In the quantum result, the von Neumann entropy S of the density operator describing an ensemble of pure quantum signal states is equal to the number of spin1/2 systems (``quantum bits'' or ``qubits'') necessary to represent the signal faithfully. The theorem holds whether or not the signal states are orthogonal. Related results are also presented about the fidelity of quantum coding and about representing entangled quantum states.
 Publication:

Physical Review A
 Pub Date:
 April 1995
 DOI:
 10.1103/PhysRevA.51.2738
 Bibcode:
 1995PhRvA..51.2738S
 Keywords:

 03.65.Bz;
 05.30.d;
 89.70.+c;
 Quantum statistical mechanics;
 Information theory and communication theory