The Quantum Engine

Modern engines are imperfect. The limitations imposed by the laws of physics do not allow achieving maximum efficiency, and some part of the energy is inevitably lost. There is, however, a curious way around these restrictions, and more recently it has been proven.

©Depositphotos

The efficiency of any engine depends on how much energy it loses during operation. Steam engines have not been widely used, therefore, because too much heat has gone not to transformation into kinetic energy (that is, into motion), but into the surrounding space.

The actual nature of the steampunk was partially prevented by nature itself, in particular - the second law of thermodynamics, according to which any closed system tends to uniform dissipation of energy-heat. This imposes certain limitations on almost any engine.

An almost insurmountable obstacle on the way to the most effective (ideal) engine is also friction in the performance of mechanical work - about the air environment, the details of the mechanism, etc.

Thus, some of the energy released during the conversion of fuel is irretrievably lost, which leads to a decrease in the efficiency of this or that engine. Systems to avoid friction and energy loss in macroscopic (that is, in large, like an automotive internal combustion engine) systems are quite difficult.

There is a logical question: can we circumvent the limitations of the macrocosm by "descending" into the microcosm?

One atom is enough

As shown by a number of studies devoted to the creation of quantum engines, it is possible. The fact is that on a quantum scale thermodynamic processes are very different. This even led scientists to the need to create a theory that would unite quantum mechanics and thermodynamics.

Within the framework of the development of such a theory of physicists, the problem of creating a quantum engine attracted, which could work absolutely without loss of energy, avoiding not only friction, but also heat exchange with the external environment. In other words, such an engine would achieve maximum efficiency.

The latest and one of the most impressive works in this direction is the research of scientists from the United States, Great Britain and Italy published in the Scientific Reports magazine, which theoretically substantiates the possibility of such an engine having adiabatic properties (i.e., lacking heat exchange with the external environment).

In particular, physicists managed to adapt Otto's cycle-the thermodynamic process, describing the action of an ideal internal combustion engine-to the scale of the micro world. They were allowed to do this by modern achievements of theoretical physics. For example, scientists have used an experimentally proven fluctuation theorem that accurately corrects the second law of thermodynamics and admits that entropy (energy dissipation) with time cannot only increase in some systems, but also decrease.

The four stages of the Otto cycle, adapted to quantum scales in which heat enters the oscillator, then goes out by doing mechanical work / ©Depositphotos

Using the so-called "shortcuts to adiabaticity," scientists showed how the engine could work based on the Otto-sized cycle of an atom. A "piston" in it would be a quantum harmonic oscillator surrounded by two microscopic chambers for supplying heat to the working body (oscillator) and its cooling. The work itself, as in the standard, non-quantum cycle of Otto, would be accomplished by compressing and expanding the working fluid.

The absence of friction would be ensured by "superadiabaticity" - a state simulating the operation of the engine in slow adiabatic processes. Calculations of scientists demonstrate that such a motor would have been very slow, but its cycle would be reversible and finite in time, which would allow it to still do some work.

And what does all this mean?

The theoretical basis for the concept of the working "super adiabatic" quantum engine is a step forward on the way to implementing the old dream of physicists - building the engine with maximum efficiency when giving out maximum power. This, of course, is not a perpetual motion machine, but also a very impressive and far more realistic prospect.

Also, this work of scientists seems useful in the development of quantum thermodynamics - a theory that would reconcile the thermodynamic processes and the physics of elementary particles.

"Thermodynamics describes processes involving many particles at once, and its quantum adaptation must also adequately reflect the many-body processes. The implementation of such concepts - like what we proposed in our work - will allow us to better control these processes, "says Mauro Paternostro of the University of Queens, UK, one of the authors of the study.

However, the practical implementation of the proposed scheme of the quantum engine is also not something fantastic and remote, the authors of the study believe. Moreover - the scientists intend to experimentally implement the engine they invented in the very near future.

Paternostro and his colleagues are already negotiating with representatives of some scientific organizations in Europe to test their theory. In particular, they want access to certain equipment to first catch a single atom with a laser, and then subject it to thermal transformations of the Otto cycle.

If physicists succeed in proving their rightness in practice, this can lead to the widespread dissemination of the most effective micro motors of quantum and nanoscale, the range of applications of which can be quite impressive.