Nature: Superconducting quantum interference devices (SQUIDs) take advantage of the ability of electrons to tunnel through thin insulators sandwiched between two Y-shaped superconductors. Francesco Giazotto and María José Martínez-Pérez of the National Enterprise for Nanoscience and Nanotechnology (NEST) in Pisa, Italy, examined SQUIDs’ ability to transfer heat and found that magnetic fields applied to the superconductors could control the rate of heat flow across the insulator. The two researchers heated one end of a SQUID and monitored the temperature of an electrode attached to the other end while they varied the magnetic field. They discovered that they could even make the heat flow from the cold end to the hot end, which apparently violates the second law of thermodynamics. As Giazotto explains it, the apparent violation is the result of using the magnetic field to shift the wavefunctions of the superconducting electrons. And the net heat flow is still from warm to cold, but that normal heat transfer does not cross the insulator barriers. The duo’s discovery proves a theory proposed in 1965 by Kazumi Maki and Allan Griffin. While there is some question whether the discovery will have practical applications, Giazotto believes it could be used to develop caloritronics, circuits that transmit information as heat, instead of electronics.