As the paper points out, there are a bunch of ways in which reversible computers will lose energy, even under ideal circumstances. It's also important not to g

As the paper points out, there are a bunch of ways in which reversible computers will lose energy, even under ideal circumstances. It's also important not to gloss over the fact that reversible circuits (e.g. CSWAP) are tremendously difficult to create, so it's unlikely we'll be seeing computers built from them anyway; and without reversible circuits at the logic gate level, you don't really gain the expected energy benefits.