The terms "subquantum" and "quantum" are not universally defined or used in the same way across different scientific contexts. However, I can provide you with a general perspective on the hierarchy of nature based on our current understanding.
Subquantum Level: This term is sometimes used to refer to the hypothetical level of reality that lies beneath or provides the foundation for the quantum level. It implies the existence of more fundamental entities or processes that underlie quantum phenomena. Some theories propose that there could be subquantum structures or dynamics that give rise to the observed behavior of quantum systems. These theories attempt to explain the origins of quantum mechanics and resolve some of its foundational puzzles, such as the measurement problem or the nature of wave-particle duality. However, it's important to note that there is no widely accepted or experimentally confirmed theory of the subquantum level at this time.
Quantum Level: The quantum level, also known as the quantum realm or quantum domain, refers to the realm of physics that deals with phenomena on very small scales, typically on the order of atoms and subatomic particles. Quantum mechanics is the theoretical framework that describes the behavior of particles and systems at this level. It is a probabilistic theory that accounts for wave-particle duality, superposition, entanglement, and other quantum phenomena. Quantum mechanics has been extensively tested and validated through experiments and is an essential part of our understanding of the physical world.
It's important to note that our current understanding of nature is primarily based on the principles and formalism of quantum mechanics, and it has been remarkably successful in explaining a wide range of phenomena. However, the nature of the subquantum level, if it exists, remains an open and active area of research in theoretical physics. The exploration of theories beyond quantum mechanics, such as hidden variables theories or approaches that incorporate ideas from quantum gravity, aims to provide a deeper understanding of the fundamental structure of reality.