Figure 1: The model.
From: Truly work-like work extraction via a single-shot analysis
The system can be in any of the states 1,…,N, each assigned an energy level (horizontal lines) h=(h1,…,hN). Two elementary operations modify the system: (a) LT. This lifts or lowers the energy levels h to a new configuration h′, but leaves the state (circle) intact. If the system is in state n, the work cost of the LT is defined as 
. (b) Thermalization with respect to a heat bath of temperature T. This changes the initial probability distribution (bars) q=(q1,…,qN) over the states, into the Gibbs distribution G(h), but leaves the energy levels h intact, and has no work cost. We build up processes by combining LTs and thermalizations.
