Optics for low-energy communication inside digital processors: quantum detectors, sources, and modulators as efficient impedance converters.

I argue that optics can reduce the energy for irreversible communication of logic-level signals inside digital switching and processing machines. This is because quantum detectors, quantum sources, and modulators can perform an effective impedance transformation that matches the high impedances of small devices to the low impedances encountered in electromagnetic propagation. Current physics and device concepts are sufficient to realize this advantage over electrical communications given appropriate integration technology. This energy argument suggests that all except the shortest intrachip communications should be optical.