# Today I Learned

Some of the things I've learned every day since Oct 10, 2016

## 4: Landauer’s Principle

Landauer’s Principle asserts that “any logically irreversible manipulation of information, such as the erasure of a bit or the merging of two computation paths, must be accompanied by a corresponding entropy increase in non-information-bearing degrees of freedom of the information-processing apparatus or its environment.”

The Landauer Limit, the minimum possible amount of energy required to erase a single bit, is

$kT \textrm{ln}2$

where $k$ is the Boltzmann constant and $T$ is the temperature of the system in Kelvins.

Notable is that this principle allows for the possibility of computation which requires no release of heat by being logically reversible, or by putting the required increase in entropy onto other conserved quantities in the system besides heat, such as angular momentum.