Generation and reconstruction of Schrodinger cat states of light in a cavity by quantum nondemolition measurements

Application of the quantum nondemolition (QND) method to Schrodinger cat states is described. Phase cat states of trapped light is generated by QND measurement of the photon number parity of a coherent field initially injected into the cavity. The measured Wigner function of a cat state at four different delays between preparation and measurement is presented. The Wigner function exhibits two positive, ideally Gaussian, peaks corresponding to the two classical components of the state. Quantitative analysis of the decoherence process is also presented. Generalization of this experiment to the preparation of non-local cat states located at the same time between two different cavities is discussed.