Multiple studies and reviews confirm that squeezed light is routinely produced using nonlinear optical processes such as parametric down-conversion and four-wave mixing.
The claim states that squeezed light is produced using nonlinear optical processes such as parametric down-conversion. Papers [0], [1], [2], [5], and [8] all directly support this by detailing the generation of squeezed states through nonlinear optical processes like parametric down-conversion or four-wave mixing. There are no papers refuting this well-established physical principle.