The fathers of thermodynamics got a lot of mileage from thought experiments about gas-filled engines conjoined to reservoirs of hot and cold. Today a few physicists are playing with quantum mechanics in hopes of finding new methods to control and create energy flow in quantum versions of the steam engine. Their research suggests that it is possible to "beat" the inviolable second law of thermodynamics with some quantum sleight-of-hand.
The second law limits the efficiency of any physical process. In essence, it states that, to perform work, energy must flow between two reservoirs set at different temperatures. The flow introduces disorder into the system. The temperature difference between the two baths determines the engine's maximum, or Carnot, efficiency, named after 19th-century French physicist Sadi Carnot.
This article was originally published with the title Law and Disorder.