Generation of optical ‘Schrödinger cats’ from photon number states

Schrödinger's fat cats The Schrödinger's cat thought experiment illustrates the idea that quantum physics allows atoms to remain in superpositions of states. The cat is imagined in a box along with a radioactive atom engineered to release a poison when it decays. In the 'classical' world the cat is either dead or alive but with the 'box' closed, in the quantum world the cat is both dead and alive at the same time. A 'cat' state of freely propagating light is defined as a quantum superposition of well separated quasi-classical states; such states may be useful for quantum information processing and in experiments to test quantum theory. Recent experiments succeeded in producing optical Schrödinger's 'kittens', too small to be of practical use. Now a combination of theory and experiment has been used to develop a protocol that generates squeezed Schrödinger cat states that are large enough to be useful for applications.