Nanoscale Quantum Computers Fundamentals, Technologies, and Future Perspectives Mehmet Keçeci ORCID : https://orcid.org/0000-0001-9937-9839, İstanbul, Türkiye Received: 23.05.2025 "Article 2 of the series" Abstract: Nanoscale quantum computers (nQCs) (first defined: Keçeci, M. (2021). Nano Quantum Computer (nQC) [Unpublished doctoral dissertation II. Report]. GTU, Kocaeli, Türkiye [320, 460]) represent a revolutionary research frontier aiming to transcend current macroscopic quantum computing approaches by integrating the fundamental principles of quantum mechanics at the most elemental level of hardware. This vision seeks to create systems not only at nanometre dimensions (1-100 nm) but also where quantum effects are dominant, operating on 100% quantum principles. Potential advantages of nQCs include enhanced coherence times, significantly reduced energy consumption, higher qubit density, and improved noise resilience. Superconductivity plays a central role in achieving these goals; its various forms, from conventional BCS theory to high-temperature superconductors and the quest for room-temperature superconductivity, underpin qubits (e.g., transmons, fluxoniums) and, crucially, p-wave symmetric superconductors capable of hosting exotic, topologically protected quasiparticles like Majorana fermions. Nanostructures such as carbon nanotubes, graphene, and other two-dimensional materials are promising building blocks for qubits, interconnects, and alternatives to Josephson junctions, like quantum dot junctions (QDJs). Manufacturing technologies necessitate a transition from micro-electromechanical systems (MEMS) to nano-electromechanical systems (NEMS) and the development of nanofabrication techniques with atomic precision. Topological insulators and superconductors are novel classes of materials characterized by topological properties, such as the Z2 invariant, offering inherent protection against decoherence. However, creating stable and scalable quantum systems at the nanoscale presents significant challenges. These include quasiparticle poisoning caused by environmental radiation (cosmic rays, natural radioactivity), decoherence mechanisms limiting coherence times, and the integration of complex error correction codes (e.g., the surface code) for fault-tolerant quantum computation. Alternative computational paradigms like quantum annealing and adiabatic quantum computation also enrich research in this domain. In the future, nanoscale quantum computers are expected to spearhead groundbreaking advancements in numerous fields, from materials science and drug discovery to optimization problems and fundamental physics research. This signifies not merely a miniaturization of existing technologies but potentially the dawn of a new computational era where quantum phenomena are harnessed in their purest form. Keywords: Nano Quantum Computer, Superconductivity, Topological Quantum Materials, Majorana Fermions, MEMS, NEMS, nQCs, Nanotechnology, Coherence, Carbon Nanotubes, Quantum Error Correction, Quantum Annealing.