Thermodynamics has shed light on engines, efficiency, and time’s arrow since the Industrial Revolution. But the steam engine has given way to small-scale, quantum, and far-from-equilibrium technologies and experiments. Nineteenth-century thermodynamics needs updating for the 21st century. Guidance comes from quantum information theory, the study of how nonclassical phenomena (e.g., entanglement) can process information in ways impossible with classical hardware. Applying quantum information theory to thermodynamics, I will show, illuminates fundamental questions (e.g., how does the second law generalize to small scales?) and motivates technologies (e.g., quantum engines). I call this combination quantum steampunk, after the steampunk genre of literature, art, and cinema that juxtaposes futuristic technologies with 19th-century settings.
I will illustrate with scrambling, equilibration in which information spreads through many-body quantum systems via entanglement. To characterize scrambling, I will introduce a quasiprobability distribution, a quantum generalization of a probability distribution. This quasiprobability has several experimental and theoretical applications. Examples include a scheme for detecting scrambling via weak measurements, which barely disturb the measured system. The quasiprobability also signals false positives in attempts to detect scrambling in open systems. Theoretically, the quasiprobability connects scrambling to nonequilibrium statistical mechanics, chaos, and uncertainty relations.
Host: Jack Harris