Refrigeration by Quantum Measurements

In Maxwell’s famous thought experiment, a demon operates a door between two gas reservoirs, collecting hotter particles in one and colder particles in the other. As we now know, the demon needs information to sort the particles, so the second law of thermodynamics is not violated. Similarly, quantum heat engines rely on information to operate a feedback control loop that steers the heat. Now, Michele Campisi at the University of Florence, Italy, and colleagues show theoretically that quantum refrigeration can be fueled by measurements alone, without exerting feedback control. Such a scheme is more tolerant of noise and may therefore be practically achievable.