The second law of thermodynamics explains the fact that heat “flows” from higher to lower temperatures in a spontaneous process in a way that maximizes disorder. Rudolf Clausius formulated a criterion for the direction in which this process takes place in 1850 and called it entropy S. Thermodynamics is one of the most successful physical theories ever formulated. Although it was originally developed to treat steam engines and in particular the problem of converting heat into mechanical work, it survived even after the scientific revolutions of relativity and quantum mechanics. Inspired by recently developed quantum resource theories, renewed efforts have been made to understand the fundamentals of quantum scale thermodynamics1,2,3,4,5,6,7,8,9,10,11, including their links to statistical mechanics12,13,14 and information theory15,16,17,18,19,20,21,22,23,24,25. However, all these approaches assume that the system is initially not correlated with the bathroom. In fact, correlations can violate the laws of thermodynamics. Especially when there are correlations between systems, phenomena such as abnormal heat flows from cold baths to hot baths26 and storage extinction in conjunction with the extraction of work instead of heat dissipation24 become possible. These two examples indicate a violation of Clausius` second law in its formulation and Landauer`s principle of suppression of information15. Due to the interrelationship between the different laws of thermodynamics, the zero law and the first law can also be violated (see additional note 4 for simple and explicit examples of these violations).

However, it does not provide any information on the direction in which processes can occur spontaneously, i.e. the reversibility aspects of thermodynamic processes. For example, FLT cannot specify how cells can perform work in an isothermal environment. FLT does not provide information on the inability of a thermodynamic process to completely convert heat into mechanical work, nor does it provide information on why mixtures cannot separate spontaneously. This requires a principle to explain these phenomena and characterize the availability of energy. This principle is embodied in the second law of thermodynamics, which we will explain later. The Second Law of Thermodynamics (SLT) summarizes the process of converting heat into work and states that heat flows spontaneously “on one side”, that is, from a higher temperature to a lower temperature. To reformulate thermodynamics, we begin by redefining heat by correctly considering the flow of information and thus restoring Landauer`s quenching principle. In general, heat is defined as the flow of energy from the environment, generally thought of as a thermal bath at a certain temperature, to a system that is somehow different from work.

Work, on the other hand, is quantified as the flow of energy, say, to a bath or to an external agent, which could be extractable (or accessible). Imagine a thermal bath with Hamilton H B and at temperature T represented by the Gibbs state (rho _{mathrm{B}} = tau _{mathrm{B}} = frac{1}{{Z_{mathrm{B}}}}{kern 1pt} {mathrm{exp}}{kern 1pt} left( {frac{{ – H_{mathrm{{B}}}}{{kT}}} right)), where k is Boltzmann`s constant and (Z_{mathrm{B}} = {mathrm{Tr}}{kern 1pt} left[ {{mathrm{exp}}left( {frac{{ – H_{mathrm{B}}}}{{kT}}} right)} right]) is the partition function. The degrees of freedom in B are considered part of a large super thermal bath at temperature T. Then, for a process that converts the thermal bath (rho _{mathrm{B}} en {rho prime} _{mathrm{B}} ) with the fixed Hamiltonian H B, the heat transfer to the bath is quantified (see note 1) as Before diving into the three main laws of thermodynamics, it is important to understand the concept of a system and the environment. Now, armed with the correct definition of heat (as in equation (3)) and work (based on generalized free energy in equation (6)) in the presence of correlations, we present the generalized laws of thermodynamics. The first and second laws were formalized in the work of the German physicist Rudolf Clausius and the Scottish physicist William Thomson around 1860. The third law was developed by German chemist Walther Nernst from 1906 to 1912. However, scientists realized that an additional law was needed to fully describe energy changes in systems. This “law” was a fundamental understanding that was always considered true, but had to be formally explained. Since the other three laws were already numbered and the supplementary law is the basis for the other three, it was called the zero law of thermodynamics by Ralph Fowler in the 1930s. The second law of thermodynamics emphasizes the irreversibility of natural processes and, in many cases, the tendency of natural processes to lead to a spatial homogeneity of matter and energy, and in particular temperature. It can be formulated in a variety of interesting and important ways.

One of the simplest is Clausius` statement that heat does not spontaneously pass from a cooler body to a warmer body. The zero law of thermodynamics tells us whether or not heat flows between two bodies. The zero law of thermodynamics states that if a body A is in thermal equilibrium with another body B and body A is also in thermal equilibrium with a body C, this implies that bodies B and C are also in equilibrium with each other. When two bodies of different temperatures are brought together, heat begins to flow from the high-temperature body to the low-temperature body until both reach the same temperature and the heat flow process stops. At this point, both bodies should be in thermal equilibrium. The zero law process of thermodynamics is illustrated in Fig. 2.4. These concepts of temperature and thermal equilibrium are fundamental to thermodynamics and were clearly formulated in the nineteenth century. The name “zero law” was coined by Ralph H.

Fowler in the 1930s, long after the first, second, and third laws were widely recognized. The law allows the definition of temperature in a non-circular way without reference to entropy, its conjugate variable. Such a definition of temperature is called “empirical”. [8] [9] [10] [11] [12] [13] The theory of thermodynamics can be summarized in its three main laws. The zero law introduces the concept of thermal equilibrium as the equivalence relation of states, where temperature is the parameter that characterizes the different equivalence classes. In particular, the transitive property of the equivalence relation implies that if a field A is in equilibrium with a field B and B is in equilibrium with a third field C, A and C are also in equilibrium. The first law guarantees energy savings. He asserts that in a thermodynamic process, not all changes in energy are of the same nature and distinguishes work, the type of energy that allows “useful” operations such as increasing a weight, and its complementary heat, any change in energy that is not work.