  Superpositions of macroscopically distinct quantum states, introduced in
Schroedinger's famous Gedankenexperiment, are an epitome of quantum
"strangeness" and a natural tool for determining the validity limits of quantum
physics. The optical incarnation of Schroedinger's cat - the superposition of
two opposite-amplitude coherent states - is also the backbone of quantum
information processing in the continuous-variable domain. However, existing
preparation methods limit the amplitudes of the component coherent states by
about 2, which curtails the state's usefulness for fundamental and practical
applications. Here we produce higher-amplitude optical Schroedinger's cats from
two such states of lower amplitudes. The protocol consists in bringing the
initial states into interference on a beamsplitter and a subsequent heralding
quadrature measurement in one of the output channels. In the experiment, we
convert a pair of negative squeezed Schroedinger's cat states of amplitude 1.25
to a single positive Schroedinger's cat of amplitude 2.15 with success
probability of ~0.2. This amplitude is comparable to the highest values
obtained for this state in any physical system. Our technique can be realized
in an iterative manner, in principle allowing creation of Schroedinger's cat
states of arbitrarily high amplitude.
