A new perspective on causality, locality and duality in entangled quantum nano systems

Interference with or without entanglement has been recognized as a key resource for quantum computing and quantum communications systems, as for example discussed by Nielsen and Chuang(1) and numerous other works. Multiple paths between sources and detectors require an understanding of the underpinning wave-particle duality issue in the interference effects. Recently a new axiom (particle and its wave function psi(r, t) cannot be coincident or co-located at space-time point (r(k), t(k)) unless psi(r, t) = delta(r-r(k), t-t(k)) the Dirac delta function) has been suggested(2) and justified, which explains duality without Niels Bohr's complementarity principle, thus eliminating the role of the observer, avoiding complicated "which way" (welcher-weg) considerations and observer subjectivity. This greatly simplifies analysis and design of multi-path quantum systems and restores objectivity. The same paper also suggested in the context of entanglement new concepts of (a) "total causality" that includes entanglement as a cause to locally and causally explain "action at a distance", and (b) "partial causality" that excludes entanglement as a cause and thereby introduces the perception of strange phenomena of non-locality, retro-causality and quantum erasure, which are nevertheless very important. This paper reviews and then applies the axiom to bring much needed clarity to certain confusing and much debated aspects of developments in non-interaction measurements, counterfactual communications and quantum computers. These potential clarifications and simplifications of analysis and design of multi path systems may help developers of future quantum communication and quantum computer systems.