  We discuss the concept and realization of a heat bath in solid state quantum
systems. First we demonstrate that, unlike a true resistor, a finite
one-dimensional Josephson junction array or analogously a transmission line
with non-vanishing frequency spacing does not strictly qualify as a
Caldeira-Leggett type dissipative environment. We then consider a set of
quantum two-level systems as a bath, which can be realized as a collection of
qubits. We demonstrate that only a dense and wide distribution of energies of
the two-level systems can secure long Poincare recurrence times characteristic
of a proper heat bath. An alternative for this bath is a collection of harmonic
oscillators, for instance in form of superconducting resonators.
