Realization of photon number amplifiers
Seng‐Tiong Ho, Horace P. Yuen · 1993
It was suggested by Yuen [1] that a photon number amplifier that transforms an input state with n photon number | n > to an output state with Gn photon number |Gn >, where G > 1 is the gain factor, is an ideal amplifier for direct detection of any signal whether it is classical or squeezed, phase coherent or incoherent [1].