  We study theoretically how loss impacts the amplification and squeezing
performance of a generic quantum travelling wave parametric amplifier. Unlike
previous studies, we analyze how having different levels of loss at signal and
idler frequencies can dramatically alter properties compared to the case of
frequency-independent loss. We find that loss asymmetries increase the
amplifier's added noise in comparison to the symmetric loss case. More
surprisingly, even small levels of loss asymmetry can completely destroy any
quantum squeezing of symmetric collective output quadratures, while nonetheless
leaving the output state strongly entangled.
