In a new paper in the journal Physical Review X FQxI quantum theorist Nicole Yunger Halpern, of the University of Maryland, College Park, and colleagues have analysed entropy when defined as an extensive thermodynamic variable, as an information-theoretic uncertainty measure, and as a quantifier of irreversibility. They have then extended the concept of entropy production to the deeply quantum regime, noting that a crucial quantum effect–the idea that certain operations in the quantum realm do not compute (for instance, it makes a difference when you choose to first to measure an object's position then its momentum or vice versa)–make have an important impact. Their work has now been featured in New Scientist (subscription required). Yunger Halpern also spoke to me about this project and its implications for understanding the nature of time in quantum systems, potentially making it easier to build quantum computers, for Templeton Ideas earlier this year. Find out more.