International. The third law of thermodynamics, developed in the early twentieth century, has a controversial past and a number of formulations due to Planck, Einstein and Nernst. Its most accepted version is the principle of unaffordability: it states that any process cannot reach absolute zero temperature in a finite number of steps and within a finite time.
In a study published in the journal Nature Communications in March 2017, Lluis Masanes and Jonathan Oppenheim "provide a derivation of the [unattainable] principle that applies to arbitrary cooling processes, even those that exploit the laws of quantum mechanics or involve an infinite dimension. They quantify the resources needed to cool a system to any temperature and translate these resources into the minimum time or number of steps, considering the notion of a thermal machine that obeys restrictions similar to universal computers.
They found that the obtainable temperature can scale as an inverse power of the cooling time. The results of the study also clarify the connection between two versions of the third law (the principle of unfathomability and the heat theorem), and put final limits on the speed at which information can be erased.
"Our goal is to provide definitive quantitative limits applicable to any cooling procedure, that is, we want to find a lower limit for the temperature that a system can reach after any process that uses some given resources or that lasts some given time. Therefore, we must allow the more general quantum transformation, that is, those that respect the conservation of total energy and are microscopically reversible (unitary). This general configuration includes thermodynamically irreversible protocols and also unrealistic protocols where full control of the microscopic degrees of freedom of the bathroom is required. Surprisingly, we will find here, as was found in the case of the second law, that having such an unrealistic degree of control does not seem to give an advantage over having very crude control.
The full report can be viewed by clicking here.
