Exception to the cloning limit—amplification of amplitude-squared squeezed states
Mark S. Hillery, D. Yu · Optical Society of America Annual Meeting · 1991
An amplifier consists of a collection of inverted two-level atoms. It can be used to amplify a light signal but in the process the fluctuation behavior of the lights will be modified. In particular, for sufficiently large gains, nonclassical input states will become classical at the output. Hong, Friberg, and Mandel examined the effect of amplification on sub-Poissonian photon statistics and normal squeezing. They found that both of these effects disappear at the output if the intensity gain |G|2 > 2. The gain |G|2 = 2 is known as the photon cloning limit because one gets two photons out for every one that goes in. This gain has stood as an upper limit for the amplification of nonclassical behavior.