Thermodynamical Analogues in Quantum Information Theory

The first step in quantum information theory is the identification of entanglement as a valuable resource. The next step is learning how to efficiently exploit this resource. We learn how to efficiently exploit entanglement by applying analogues of thermodynamical concepts. These concepts include reversibility, entropy, and the distinction between intensive and extensive quantities. We discuss some of these analogues and show how they lead to a measure of entanglement for pure states. We also ask whether these analogues are more than analogues, and note that, locally, entropy of entanglement is thermodynamical entropy.