  Macroscopic quantum systems (MQS) are macroscopic systems driven by quantum
rather than classical mechanics, a long studied area with minimal success till
recently. Harnessing the benefits of quantum mechanics on a macroscopic level
would revolutionize fields ranging from telecommunication to biology, the
latter focused on here for reasons discussed. Contrary to misconceptions, there
are no known physical laws that prevent the development of MQS. Instead, they
are generally believed universally lost in complex systems from environmental
entanglements (decoherence). But we argue success is achievable MQS with
decoherence compensation developed, naturally or artificially, from top-down
rather current reductionist approaches. This paper advances the MQS field by a
complex systems approach to decoherence. First, why complex system decoherence
approaches (top-down) are needed is discussed. Specifically, complex adaptive
systems (CAS) are not amenable to reductionist models (and their master
equations) because of emergent behavior, approximation failures, not accounting
for quantum compensator mechanisms, ignoring path integrals, and the subentity
problem. In addition, since MQS must exist within the context of the classical
world, rapid decoherence and prolonged coherence are both needed. Nature has
already demonstrated this for quantum subsystems such as photosynthesis and
magnetoreception. Second, we perform a preliminary study that illustrates a
top-down approach to potential MQS. In summary, reductionist arguments against
MQS are not justifiable. It is more likely they are not easily detectable in
large intact classical systems or has been destroyed by reductionist
experimental set-ups. This complex systems decoherence approach, using top down
investigations, is critical to paradigm shifts in MQS research both in
biological and non-biological systems.
