Quantum Effects at the Nanoscale: A Comparative Study of Jaynes-Cummings-Hubbard and Bose-Hubbard Models

As the characteristic dimensions of a physical system shrink to the nanometer scale, its behavior is governed primarily by quantum mechanics rather than by classical laws. In this regime, effects such as barrier tunnelling, energy quantization, and quantum coherence play a central role in how nanoscale devices function. These phenomena are particularly prominent in platforms such as graphene and semiconductor quantum dots, where they have a pronounced impact on transport properties, optical behavior, and overall device performance. In parallel, lattice-based many-body models offer a concise theoretical framework for describing collective quantum states in engineered structures. The present work provides a conceptually oriented survey that links quantum phenomena at the nanoscale to two benchmark lattice Hamiltonians, namely the JaynesCummings-Hubbard (JCH) and Bose-Hubbard (BH) models. The approach is qualitative and literature-based: results from quantum optics, cold-atom physics, and condensed-matter research are combined to interpret how the parameters of these models relate to experimentally tunable quantities, such as coupling strengths, confinement scales, and interaction energies. The main outcome of the review is threefold. First, tunnelling, graphene, and quantum dots can be viewed as natural settings where effective Hubbard-type descriptions arise. Second, despite describing different degrees of freedom-hybrid light-matter polaritons in the JCH case and interacting bosons in the BH case, both models display analogous phase structures with insulating and superfluid-like regimes. Third, reliable implementation of these phases in nanotechnological devices requires a careful mapping between abstract Hamiltonian parameters and specific design variables. The discussion indicates that JCHand BH-type models should be regarded not only as abstract theoretical constructs but also as practical tools for guiding the design of future quantum technologies. Extensions to driven-dissipative dynamics and topological band structures are identified as promising directions for next-generation quantum simulators and nanoscale sensors.