Abstract

A simple optical arrangement using polarization rotators and a single-pass parametric amplifier is being used to evade backaction noise in a measurement of a quadrature component of the light field.¹ The transmitted field component is left in an eigenstate with an eigenvalue equal to the measured field value. The degree of precision for this eigenvalue can be made arbitrarily high as the optical losses are decreased and the parametric gain is increased. Measurement of the field is accomplished by a homodyne detection of a polarization component orthogonal to the incident and transmitted field. A pulse mode-locked Nd:YAG laser is used as a light source for the measured field and as a pump for the KTP parametric amplifier. If a direct detection measurement is made, instead of homodyne detection, the transmitted light is left in a state which has the properties of a Schrodinger cat,² or more precisely, a Schrodinger kitten since the feasible experiments will only allow a small number of photons per cat. This catlike state can be transformed by a parametric amplifier into a state that is nearly the superposition of two coherent states. A homodyne measurement can demonstrate the quantum coherence of these two states.

© 1989 Optical Society of America