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We suggest a scheme to generate a macroscopic superposition state (``Schr\"odinger cat state'') of a free-propagating optical field using a beam splitter, homodyne measurement, and a very small Kerr nonlinear effect. Our scheme makes it possible to reduce considerably the required nonlinear effect to generate an optical cat state using simple and efficient optical elements.
Jeong et al. (Thu,) studied this question.