  We study the fluctuation-induced dissipative dynamics of the quantized center
of mass motion of a polarizable dielectric particle trapped near a surface. The
particle's center of mass is treated as an open quantum system coupled to the
electromagnetic field acting as its environment, with the resulting system
dynamics described by a quantum Brownian motion master equation. The
dissipation and decoherence of the particle's center of mass are characterized
by the modified spectral density of the electromagnetic field that depends on
surface losses and the strength of the classical trap field. Our results are
relevant to experiments with levitated dielectric particles near surfaces,
illustrating potential ways of mitigating fluctuation-induced decoherence while
preparing such systems in macroscopic quantum states.
