Landauer's Principle

Bit erasure costs at least kT·ln2 of energy — information is physical

Double-Well Potential + Particle Distribution
Erasure Protocol: Reset to |0⟩
Left well = |0⟩
50%
Right well = |1⟩
50%
Landauer limit:
Emin = kT·ln2
= 0.208 × ε

Heat dissipated: 0.00 × ε
Landauer 1961: Logically irreversible
operations must dissipate heat.
Bit erasure: 1 bit → 0 bit
requires at least kT·ln2 energy.

Maxwell's demon paradox:
The demon's memory erasure
saves the second law — Bennett
1982: measurement is free,
erasure costs.

Verified experimentally
Bérut et al, Nature 2012