The Second Law of Thermodynamics and Entropy-Decreasing Processes With $^4$He Superflows

We review on a recently proposed quantum exception to the second law of thermodynamics. We emphasize that $^4$He superflows, like any other forms of flows, shall carry entropy or heat in a thermal environment. Following that, one can use a heterogeneous $^4$He superflow loop to realize entropy-decreasing processes. We also mention that the heat content of a superflow has an unusual dependence on flow velocity, which is an important factor contributing to the entropy-decreasing processes.