Two teams of physicists are building tiny machines designed to operate with the maximum possible efficiency. According to thermodynamics, there’s an ultimate limit to the efficiency of machines known as heat engines — including steam engines and car engines — which convert heat into motion or other types of energy (SN: 3/19/16, p. 18). But real-world engines never reach that maximum efficiency, and often run well below it, because they lose energy to friction.

Now, quantum experiments are circumventing the limitations imposed by friction using specially designed shortcuts. Physicists Adolfo del Campo and Roberto Serra described two separate experiments June 25 and June 28 at the Quantum Thermodynamics meeting at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara.

The shortcuts are “a kind of quantum lubricant,” says Serra, of the Federal University of ABC in Santo André, Brazil. Similar to the way that oil can decrease friction in a standard engine, these shortcuts eliminate the friction that is present on quantum scales.

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