from the there's-still-plenty-of-room-at-the-bottom dept.
Quantum Mechanics Trumps the Second Law of Thermodynamics at the Atomic Scale:
Two physicists at the University of Stuttgart have proven that the Carnot principle, a central law of thermodynamics, does not apply to objects on the atomic scale whose physical properties are linked (so-called correlated objects). This discovery could, for example, advance the development of tiny, energy-efficient quantum motors. The derivation has been published in the journal Science Advances.
Internal combustion engines and steam turbines are thermal engines: They convert thermal energy into mechanical motion—or, in other words, heat into motion. In recent years, quantum mechanical experiments have succeeded in reducing the size of heat engines to the microscopic range.
"Tiny motors, no larger than a single atom, could become a reality in the future," says Professor Eric Lutz from the Institute for Theoretical Physics I at the University of Stuttgart. "It is now also evident that these engines can achieve a higher maximum efficiency than larger heat engines."
Scientists break 200-year-old principle to create atomic engines that power future nanobots:
A research team in Germany has achieved a stunning theoretical breakthrough that could reshape one of physics' oldest foundations after demonstrating that the no longer holds true for objects on the atomic scale.
Their findings, made by Eric Lutz, PhD, a physics professor and Milton Aguilar, PhD, a postdoctoral researcher at the University of Stuttgart, show that quantum systems can exceed efficiency limit defined by the Carnot principle.
The law, which was developed by French physicist Nicolas Léonard Sadi Carnot in 1824, is a central law of thermodynamics that has remained unchallenged for two centuries.
It states that all heat engines operating between the same two thermal or heat reservoirs can not have efficiencies greater than a reversible heat engine operating between the same reservoirs.
"Our results provide a unified formalism to determine the efficiency of correlated microscopic quantum machines," the two physicists stated.
According to the researchers, Carnot determined the maximum efficiency of heat engines. He developed his principle, the second law of thermodynamics, for large, macroscopic objects, such as steam turbines.
"However, we have now been able to prove that the Carnot principle must be extended to describe objects on the atomic scale – for example, strongly correlated molecular motors," the researchers stated.
However, while Carnot showed that the greater the difference between hot and cold, the higher the maximum possible efficiency of a heat engine, the principle neglects the influence of so-called quantum correlations.
Contrary to previous understandings the two researchers discovered that once you enter the quantum realm, where particles become correlated, interacting in ways that defy classical physics, the Carnot efficiency limit begins to crumble.
"These are special bonds that form between particles on a very small scale," they said. "For the first time, we have derived generalized laws of thermodynamics that fully account for these correlations."
Their results indicate that thermal machines functioning at the atomic scale are capable of converting not only heat but also correlations into usable work. What's more, these systems can generate more output, allowing the efficiency of a quantum engine to exceed the conventional Carnot limit.
Journal Reference: https://www.science.org/doi/10.1126/sciadv.adw8462
(Score: 5, Interesting) by pTamok on Saturday November 01, @09:04AM (2 children)
I don't understand it, which is fine: it gives me a target to reach for.
From a physics point of view, the small scale does have apparently counter-intuitive results. For example, individual particle interactions are insensitive to the 'arrow of time': you can run an interaction forwards or backwards and there is nothing intrinsic that tells you which way time is flowing*, but at a macroscopic scale, entropy tells you. I would expect that a proper treatment of the theory supporting this is that at a macroscopic level the behaviour will tend towards that of classical physics. There will likely be a reason why you can't scale up a microscopic 'violation' of the Second Law to macroscopic levels.
*This is not exactly true. T-symmetry [wikipedia.org] breaks down where there are charge-parity symmetry [wikipedia.org] is not conserved. Hence CPT-symmetry theory [wikipedia.org]. So you can determine which way time is flowing in our Universe by looking at CP-violations.
(Score: 2) by HiThere on Saturday November 01, @01:25PM
I expect that it *could* scale up to the macro level, but that doing so would require extreme care...so much so that the entire system that contained both the engines and the conditions necessary for them to work would, itself, meet the conditions of thermodynamics. Consider Bose-Einstein condensates as an analogy.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by VLM on Saturday November 01, @02:47PM
Thats a pretty good one line summary of the entire field of statistical thermodynamics. It works pretty well on macro scale simulated problems.
However, what's the macro-scale statistics of maybe literally one isolated anecdotal quantum particle? That question doesn't seem to make much sense in the context of Carnot and statistical thermodynamics, I'm picking on the paper about that.
Usually the way its taught in school is you learn basic thermodynamics first, then in statistical physics it turns out that if you do statistical analysis or massive simulation of many particles you end up with results that match the observed large scale stuff in the thermodynamics textbook. It butts up against fluid dynamics (everything that moves is a fluid, kinda) and information theory (like whats the "information" stored in the well known crystal lattice of ice when it melts?)
https://en.wikipedia.org/wiki/Eigenstate_thermalization_hypothesis [wikipedia.org]
So it all boils down to if you want to do "quantum thermodynamic stuff" should you look at it like really messed up fluid dynamics or look at it like observable quantum states. The ETH dudes think the former leads to madness (honestly probably correct) and the latter makes theoretical mathematical sense although it seems very hard to apply. The dudes in the article seem to be of the former camp, build it and we'll explain the results later, rather than the latter camp. Or the ETH dudes are trying to explain it from the theoretical side out and got stuck pretty well, whereas the dudes in the article are trying to go the opposite direction lets make an experiment (even if only thought experiment) and move inward to the theoretical once we get a result (if we get a result)
(Score: 0) by Anonymous Coward on Saturday November 01, @12:09PM (1 child)
... we will have to replace Schroedinger's cat with Trump's cat?
Somehow I don't see Trump's cat surviving past its current term!
--
Just because you have the right to remain insane doesn't make it a good idea!
(Score: 3, Insightful) by c0lo on Sunday November 02, @01:40AM
Cat? No, the correct term in the context is pussy
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by VLM on Saturday November 01, @02:28PM (4 children)
My understanding of the whole topic boils down to there is no such thing as a Carnot cycle as isolated quantum atomic (in the database sense) actions.
If, on a large macroscopic scale, you have two reversible adiabatic and two isothermal actions, THEN the large macroscopic scale system seems to have certain behaviors including a max efficiency as per Carnot regardless of design or working fluid, etc.
Everyone knows what adiabatic and isothermal mean in a large system. There's long wordy rules-lawyering explanations but adiabatic means the engine part during this part of the cycle is well insulated so the internal temp will undergo some swings. Isothermal means the temp is constant because its perfectly poorly insulated. Both processes are very idealized and no chemical changes occur (LOL) and there's no phase changes (LOL). Carnot is basically a simplified mental model of a continuous operation car engine type device.
So what does abiabatic and isothermal mean if you only have a couple quantum thingies very much non-thermalized with a dose of Heisenberg uncertainty principle? Doesn't mean a whole hell of a lot, I guess. Whats the "temperature" of a reservoir that contains a very small number of non-thermalized quantum particles. What is "heat" at the quantum level around Heisenberg limits? Well the Carnot model doesn't seem to apply.
Now what remains to be seen is we already have giant macroscopic systems made entirely of abstracted quantum particles like steam engines and IC engines etc and nobody has found a way to stick very large collections of quantum particles together to make a human sized engine that violates Carnot. Or, by very careful rules lawyering, a fuel cell that oxidizes fuel generating some heat can exceed Carnot because its "not really a Carnot Engine" in the abstract mental model sense. I mean in a hand waving way, batteries are a way to turn chemical potential energy into electricity without using heat so they're not limited by Carnot either.
The abstract and intro below help a lot:
https://link.springer.com/article/10.1140/epjp/s13360-025-06211-5 [springer.com]
My gut level guess of how this will pan out is you'll have some rules lawyering about the precise definition of Carnot cycle limits to eliminate quantum foolishness from being considered as itty bitty steam engines, and there will be some quantum scale micromachine thats more efficient than a steam engine kinda like fuel cells.
Yeah in a certain sense incandescent bulbs and LEDs are "the same" they turn electrical energy into light with some waste heat, some more than others. But as an operating principle a high efficiency LED is not just a silicon filament running at a trillion degrees to reach the same efficiency specs as an incandescent at a theoretical trillion degrees. They operate in totally different unrelated ways so its not useful to discuss how a LED is an incandescent with a really hot resistive filament or describe an incandescent as a LED with quantum tungsten diode junctions.
In the long run this will be interesting, and possibly have some real-world impact, but its a false dilemma to even bring Carnot into the discussion.
Some discussion of related stuff is very old indeed. I remember reading decades ago in Feynman's Lectures about how a quantum "Maxwells Demon" can't be built out of rachets and pawls because they would heat up in operation until thermal jitter made them not work reliably anymore (essentially melt or evaporate).
There's probably some analogy with the double slit experiment from the oldest days of QM, where you're not actually changing oceanographic geophysics tides and waves at a large scale, regardless of the outcome of the microscopic experiment. Thats kind of the entire point, the rules are different down there.
(Score: 3, Interesting) by VLM on Saturday November 01, @02:51PM (1 child)
Oh I just thought of the perfect analogy:
abiabatic is like the perfect electrical insulator, isothermal is like the perfect electrical conductor, and this quantum heat engine stuff is like semiconductor transistors and tunneling electrons thru band gaps and similar electrical quantum woo woo.
I guess there is some benefit to drinking my morning tea before shitposting as it took about two glasses to gin that up.
(Score: 2) by sjames on Sunday November 02, @06:11AM
Nice turn of phrase. I'll make a note of it.
(Score: 1) by khallow on Saturday November 01, @03:46PM (1 child)
The rule lawyering has already begun. The exceptions mentioned in the paper are already classified and quantified as loss of quantum correlations. While I haven't gone through these papers (or other papers in references), it sounds like they've already come up with quantum versions of these heat engines.
One thing that is interesting is the possibility for very efficient heat transfer. For example, create 10 to the ludicrous power of quantum correlations in one place, transfer them to another place via electricity or EM radiation like light, and then locally cool a distant location via breaking of those correlations.
(Score: 1) by khallow on Saturday November 01, @03:51PM
(Score: 2) by Subsentient on Saturday November 01, @05:51PM
Research discrediting the second law of thermodynamics tends to result in researchers committing suicide by shooting themselves in the back of their head, three times.
"It is no measure of health to be well adjusted to a profoundly sick society." -Jiddu Krishnamurti
(Score: 4, Interesting) by maxwell demon on Saturday November 01, @05:58PM (1 child)
Looking at the paper, I notice the following sentence (emphasis by me):
Correct me if I'm wrong, but to me that sounds as if they explicitly assume a system that violates the first law of thermodynamics, which is energy conservation.
I'm not surprised that if you explicitly violate the first law of thermodynamics, you can also find a violation of the second law of thermodynamics.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 3, Funny) by c0lo on Sunday November 02, @01:46AM
You traditionalist you
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by istartedi on Saturday November 01, @07:35PM (1 child)
Has Quantum Mechanics appointed a lot of judges?
Appended to the end of comments you post. Max: 120 chars.
(Score: 2) by c0lo on Sunday November 02, @01:49AM
Oh, well, you may be onto something here, but "a lot" is relative and QM is not yet reconciled with GR.
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford