  A reciprocating quantum refrigerator is analyzed with the intention to study
the limitations imposed by external noise. In particular we focus on the
behavior of the refrigerator when it approaches the absolute zero. The cooling
cycle is based on the Otto cycle with a working medium constituted by an
ensemble of non interacting harmonic oscillators. The compression and expansion
segments are generated by changing an external parameter in the Hamiltonian. In
this case the force constant of the harmonic oscillators $m \omega^2$ is
modified from an initial to a final value. As a result, the kinetic and
potential energy of the system do not commute causing frictional losses. By
proper choice of scheduling function $\omega(t)$ frictionless solutions can be
obtained in the noiseless case. We examine the performance of a refrigerator
subject to noise. By expanding from the adiabatic limit we find that the
external noise, gaussian phase and amplitude noises, reduce the amount of heat
that can be extracted but nevertheless the zero temperature can be approached.
