A sufficient set of experimentally implementable thermal operations

TL;DR

This paper demonstrates that a simple set of two thermal operations, involving energy level adjustments and two-level thermalizations, suffices to achieve all state transformations allowed by quantum thermodynamics laws, making these laws experimentally accessible.

Contribution

It shows that the complex second laws of quantum thermodynamics can be saturated with just two simple operations and an ancilla, bridging theory and experimental implementation.

Findings

Two simple operations suffice to saturate quantum thermodynamic laws.

Any state transformation allowed by second laws can be achieved with these operations.

The results establish the physical relevance of quantum second laws in experimental settings.

Abstract

Recent work using tools from quantum information theory has shown that at the nanoscale where quantum effects become prevalent, there is not one thermodynamical second law but many. Derivations of these laws assume that an experimenter has very precise control of the system and heat bath. Here we show that these multitude of laws can be saturated using two very simple operations: changing the energy levels of the system and thermalizing over any two system energy levels. Using these two operations, one can distill the optimal amount of work from a system, as well as perform the reverse formation process. Even more surprisingly, using only these two operations and one ancilla qubit in a thermal state, one can transform any state into any other state allowable by the second laws. We thus have the remarkable result that the second laws hold for fine-grained manipulation of system and bath, but can be achieved using very coarse control. This brings the full array of thermal operations into a regime accessible by experiment, and establishes the physical relevance of these second laws.