Quantum Information Processing, Vol. 7, Nos. 2/3, June 2008 (© 2008)
Quantum Shared Broadcasting
and A. S. Holevo
Received November 30, 2007; accepted February 6, 2008; Published online: April 5, 2008
A generalization of quantum broadcasting protocol is presented. Here the goal is
to copy an unknown input state into two subsystems which partially overlap. We
show that the possibility of implementing these protocols strongly depends upon
the overlap among the subsystems. Conditions for approximated shared broadcast-
ing are analyzed.
KEY WORDS: quantum broadcasting; entanglement; cloning.
PACS: 03.67.Hk; 03.65.-w.
The no-cloning theorem
is an important property of quantum mechan-
ics which follows from the linear structure of the theory. In its weaker
version the no-cloning theorem formalizes the physical impossibility of
creating a machine that produces exact copies of an unknown, given quan-
tum state. More generally it prevents us to construct a machine such that,
randomly choosing one of two non-orthogonal states of a system, it will
produce perfect copies of such state.
Together with entanglement (of which it is a direct consequence) the
no-cloning theorem contributed in modifying our approach to informa-
tion theory and in reﬁning our intuition about quantum-based information
with profound consequences both in quantum computation
and in quantum communication. In particular it played an important role
in the development of quantum error correction techniques
ing one from having codes that create redundant copies of every state of
a quantum system.
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