2023-06-23 04:00:04
Researchers show in a recent article that it is possible to coherently extend thermodynamics, initially designed to describe energy exchanges between macroscopic systems, to extremely small systems, where fluctuations and quantum properties are dominant and endow these exchanges with completely new characteristics.
Thermodynamics is a physical theory developed (In geometry, the evolute of a plane curve is the locus of its centers of…) during the 19th century with the aim of rationalizing the empirical development of steam engines, which had begun in the previous century. The objective was to transform as efficiently as possible the heat, uncontrolled energy produced by the combustion (Combustion is an exothermic chemical reaction of oxidation-reduction. When the…) of coal, in movement – to move the locomotives by example.
Image d’illustration Pixabay
Until today, optimizing the transformation of heat into “useful” energy (also called “work”), such as the movement of a vehicle (A vehicle is a mobile machine, which makes it possible to move people or loads of ‘un…) or the production of an electric current (An electric current is the displacement of a set of charge carriers…), remains one of the major applications of thermodynamics, the concepts of which are also found in heart of all major areas of modern macroscopic physics.
Nevertheless, research in this field took a new turn in recent decades, when scientists wanted to describe energy exchanges involving microscopic systems such as molecules and individual DNA strands. At these scales, the fluctuations, consequences of the disordered shocks that the molecules have between them (and which are the true nature of what, macroscopically, we call the temperature) are dominant, and the generalization (Generalization is a process which consists in abstracting a set of…) from the microscopic world of thermodynamic concepts is not self-evident.
Even more recently, the “second” quantum revolution, linked to the progress made in the precise manipulation of elementary objects (electrons, atoms, photons…), has attracted the interest of physicists towards the elaboration of a thermodynamics which would apply to quantum systems. These have unique properties, such as the emergence of quantum fluctuations, a form of fundamental uncertainty that persists even in the event of control (The word control can have several meanings. It can be used as a synonym for examination, …) perfect on the system, or coherent superpositions, for which the quantum system finds itself “simultaneously” in several different states.
In a recent work, researchers from the Physics Laboratory of the ENS de Lyon (LPENSLCNRS / ENS de Lyon) and the Computer Science Laboratory (Computer science – contraction of information and automation – is the field…) of parallelism (LIP, CNRS / ENS de Lyon / University (A university is a higher education institution whose objective is the…) Claude Bernard) were interested in the problem of formulation (Formulation is an industrial activity consisting in manufacturing products…) of thermodynamics on a quantum scale, in the presence of these phenomena without equivalents in the classical world. They showed that it is possible to develop a formalism allowing to unambiguously define the thermodynamic notions of heat and work for sets of interacting quantum systems (An interaction is an exchange of information, affects or energy between two agents within…), whatever their size and condition.
Moreover, by identifying the non-thermal energy contained in a system, the developed theory makes it possible to quantify all the resources of the quantum world which can be used as work. This includes properties analogous to classical systems, such as compressing a spring, but also purely quantum properties such as coherent superpositions of states of different energies. One of the surprising consequences of these results is that any quantum system can behave as a simultaneous source of work and heat.
Illustration of the interaction between various quantum systems.
In this artist’s view, the circular systems represent atoms while the elongated system represents an electromagnetic mode. Different colors represent different states. The exchanges of energy result in exchanges of heat and work, now defined at the level of the single quantum system, and represented respectively by “flames” and “batteries”. Note that each quantum subsystem is always capable of exchanging both heat and work.
© C. Elouard et C. Lombard Latune
To illustrate this new physics, they propose a compact “machine” where a qubit A (basic quantum system used in particular by quantum computers) is cooled (its entropy strictly decreases) thanks to the work provided by a second qubit B, hotter than A. Cooling is therefore possible thanks to the work provided by qubit B by consuming “non-thermal” resources (in our case a superposition (In quantum mechanics, the principle of superposition stipulates that the same quantum state can…) coherent state of different energies). Compared to conventional conventional refrigerators (or alternatively to “quantum” refrigerators designed so far), composed of a cold thermal bath, a hot thermal bath and a working source, everything happens as if A were playing the role of the cold thermal bath, and B simultaneously played the role of the hot bath and the source of work. These results open the way to the realization of extremely compact elementary thermal machines that might be used by quantum devices as an energy source or a system for regulating the flow of energy and entropy. Possible applications in biology around the modeling of cellular motors and the capture of solar energy (Solar energy is the energy that the sun dispenses by its radiation, directly or from…) are also possible. These results are published in the journal PRX Quantum.
Reference
Extending the Laws of Thermodynamics for Arbitrary Autonomous Quantum Systems
C. Elouard and C. Lombard Latune, PRX Quantum, published on April 18, 2023.
DOI: 10.1103/PRXQuantum.4.020309
Open archive: arXiv
1687528994
#quantum #energy #exchanges
