All machinery, big and small, uses some form of energy to carry out its function. Cars use gasoline, computers use electricity and plants use light. The way that energy is used in a machine is known as energy coupling. For instance, in a car the chemical potential energy stored in gasoline is coupled to the turning of the wheels. In a computer, electrical potential energy is coupled to the logical computations carried out by the processor. Similarly, plants couple the energy from light to the synthesis of energy containing sugars, which in turn provide the fuel for most of the biomolecular nanotechnology in existence, i.e. life.

A major problem in useful coupling results from the second law of thermodynamics (entropy) which says that no coupling can be 100% efficient. That is, some energy is always lost in each coupling event. Still, some coupling is more efficient that other coupling. Even our most fuel efficient engines use most of the energy produced by burning fuel to create heat, with only a fraction resulting in useful motion. In contrast, molecular motors in our muscles and brains known as actomyosin complexes couple energy from ATP into mechanical motion with nearly 100% thermodynamic efficiency. This is possible because the nanoscale heat engine is able to efficiently couple the energy stored in an ATP molecule to the formation of a local temperature near absolute zero. However, coupling that nanoscale motion to macroscale motion such as muscle contraction lowers the efficiency to about 60%. While this value is still much greater than our best macroscale engines, it illustrates the difficulties involved in converting nanoscale energy into macroscale motion.

Quantum computing is a mysterious sounding method that can best be understood as an approach to computation that seeks to use coupling on the smallest possible scale (quantum coupling) to carry out logical operations. For instance, spin-spin coupling in nuclear magnetic resonance is a quantum mechanical phenomena in which the spin states of 2 particles are shared. Such quantum coupling is being used to develop Quantum Computers at IBM and in a search for Quantum Consciousness by Stuart Hameroff.