Amplification of Quantum Entanglement
F. De Martini · Physical Review Letters · 1998
The new process of quantum injection into an optical parametric amplifier operating in entangled configuration is adopted to ``amplify'' into a large dimensionality spin- $\frac{1}{2}$ Hilbert space the quantum entanglement and superposition properties of the photon couples generated by parametric down-conversion. The structure of the Wigner function and of the field's correlation functions shows a decoherence-free multiphoton Schroedinger-cat behavior of the emitted field which is largely detectable against the squeezed-vacuum noise.