Enlarging optical entanglement

We present two experiments aimed at constructing larger entangled states out of smaller ones. The meaning of "larger" is different in these experiments. In the first one, the new state contains as much entanglement as the initial one (one ebit), but one of its parts is made macroscopic by means of phase space displacement. We discuss whether such a state can be considered a true "Schroedinger cat" and why this state is robust to losses in spite of its macroscopicity. In the second experiment, we apply the photon annihilation operator to both channels of the two-mode squeezed state, thereby achieving a larger amount of both squeezing and entanglement. Both experiments have their own circle of applications in quantum information technology and fundamental physics.