Traditional processors are typically based on silicon, however, researchers have developed experimental processors based on alternative materials such as carbon nanotubes, graphene, and alloys made of elements from groups three and five of the periodic table. Further, transistors made out of a single sheet of silicon atoms one atom tall and other 2D materials have been researched for use in processors.
The progress of processors has followed Moore's law closely, the theory that the number of transistors in processors will double every two years.
Photonic processors are based on using light to make computations instead of semiconducting electronics. Processing is done by photodetectors sensing light produced by lasers inside the processor.
^Sun, Chen; Wade, Mark T.; Lee, Yunsup; Orcutt, Jason S.; Alloatti, Luca; Georgas, Michael S.; Waterman, Andrew S.; Shainline, Jeffrey M.; Avizienis, Rimas R.; Lin, Sen; Moss, Benjamin R. (December 2015). "Single-chip microprocessor that communicates directly using light". Nature. 528 (7583): 534–538. doi:10.1038/nature16454. ISSN 0028-0836.