In the spirit of quantum nondemolition measurement we show that repeatedly measuring the atomic state of a trapped ion subjected to suitable vibronic couplings it is possible to extract interesting nonclassical states. The possibility of generating angular momentum Schrödinger cat is demonstrated.
We discuss a simple implementation of a quantum nondemolition measurement of the vibronic state of a trapped ion. This scheme allows the production of Fock states associated to the center-of-mass motion and the determination of the population distribution of the trap levels, and is based on the vibronic level dependence of the frequency of Rabi oscillations between two internal states of the ion, induced by a resonant carrier field. The same scheme can be used to produce a Schr\"odinger-cat-like state after a single interaction between the trapped ion and the carrier pulse, followed by the detection of the ionic internal state. \textcopyright{} 1996 The American Physical Society.
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.