  We demonstrate that a phase-independent quantum amplifier of a polarization
qubit is a complementary amplifier of the heralded qubit amplifier [N. Gisin,
S. Pironio and N. Sangouard, Phys. Rev. Lett. 105, 070501 (2010)]. It employs
the multi-functional cloner in 1 to 2 copying regime, capable of providing
approximate copies of qubits given by various probability distributions, and is
optimized for distributions with axial symmetry. Direct applications of the
proposed solution are possible in quantum technologies, doubling the range
where quantum information is coherently broadcast. It also outperforms natural
nonlinear amplifiers that use stimulated emission in bulk nonlinear materials.
We consider the amplifier to be an important tool for amplifying quantum
information sent via quantum channels with phase-independent damping.

Quantum Physics