D. Energy Recovery

According to the fundamental principles of information processing there is no need for power dissipation as long as no information is observed or thrown away [29,58]. ^D.1 It was also shown that, in principle, any logical function can be realized without dissipating any energy. The basic idea of lossless computation is to prevent the interaction with the thermal environment as far as possible, i.e., to make the computations adiabatic.

Clearly, lossless computation is based on idealized assumptions, and in a real-world scenario, especially, in a CMOS VLSI technology it will be difficult to realize. Consequently, there is a lot of controversy about the potential leverage. Yet, in particular points of interest adiabatic concepts may offer considerable improvements in terms of power efficiency.

Footnotes

...fredkin,A0600. ^D.1

For example, when two M-bit numbers are multiplied, the multiplication requires no energy and neither does the truncation of the 2M-bit result to M bits, provided, the energy of the removed bits is recycled. However, when a result is observed, its energy is lost, i.e., converted to thermal energy.