Quantum statistics of a two-mode SU(1,1) interferometer
Ulf Leonhardt · Physical Review A · 1994
A comprehensive formalism for a two-mode SU(1,1) interferometer (a nondegenerate parametric amplifier, a degenerate four-wave mixer, or a phase-conjugating mirror) is presented. The device changes the quantum state of the two incident modes by an SU(1,1) transformation. Apart from phase shiftings, the quadrature wave functions are Lorentz transformed. A transformation formula in the Fock space of the two modes is derived. Hybrids of s and -s quasiprobability distributions are changed by the inverse-mode transformation. It is related to quantum noise in phase conjugation. Linear amplification caused by Gaussian reservoirs corresponds exactly to a heuristic nondegenerate-parametric-amplifier model. It allows a simple geometrical explanation for the sensitivity of squeezing or quantum superposition with respect to phase-sensitive amplification.