DESTRUCTION OF HIGHER-ORDER SQUEEZING BY THERMAL NOISE

We examine the influence of thermal noise on several non-classical pro perties of squeezed number states. In order to evaluate arbitrary-orde r moments of both amplitude and quadrature operators of the superposit ion, we use a normal-ordering technique based on McCoy's theorem. Our analytical results are compact formulae involving Gauss hypergeometric functions. We find that the thermal mean occupancy sufficient to dest roy squeezing to any order is less than 1/2. Other non-classical featu res of a squeezed number state, such as painwise oscillations in the p hoton number distribution, sub-Poissonian statistics and amplitude-squ ared squeezing disappear completely above this threshold.