Posts Tagged ‘Maxwell’s demon

Maxwell’s Demon Meets Nonequilibrium Quantum Thermodynamics

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 Following measurements of a spin system driven out of thermal equilibrium (red), Serra and colleagues’ Maxwell's demon (blue) implements feedback control on the system’s dynamical state [2]. The control is similar to that of a parachute, smoothening the transition of the system from one state to another and rectifying the associated entropy production.
Experimental rectification of entropy production by a Maxwell’s Demon in a quantum system
P. A. Camati, J. P. S. Peterson, T. B. Batalhão, K. Micadei, A. M. Souza, R. S. Sarthour, I. S. Oliveira, R. M. Serra

Maxwell’s demon explores the role of information in physical processes. Employing information about microscopic degrees of freedom, this “intelligent observer” is capable of compensating entropy production (or extracting work), apparently challenging the second law of thermodynamics. In a modern standpoint, it is regarded as a feedback control mechanism and the limits of thermodynamics are recast incorporating information-to-energy conversion. We derive a trade-off relation between information-theoretic quantities empowering the design of an efficient Maxwell’s demon in a quantum system. The demon is experimentally implemented as a spin-1/2 quantum memory that acquires information, and employs it to control the dynamics of another spin-1/2 system, through a natural interaction. Noise and imperfections in this protocol are investigated by the assessment of its effectiveness. This realization provides experimental evidence that the irreversibility on a non-equilibrium dynamics can be mitigated by assessing microscopic information and applying a feed-forward strategy at the quantum scale.

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Written by physicsgg

December 5, 2016 at 8:30 pm

Maxwell’s demon as a self-contained, information-powered refrigerator

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Scientists created a nano-scale device that may facilitate the design of future computers, for example.

An autonomous Maxwell's demon. When the demon sees the electron enter the island (1.), it traps the electron with a positive charge (2.). When the electron leaves the island (3.), the demon switches back a negative charge (4.). Image: Jonne Koski.

An autonomous Maxwell’s demon. When the demon sees the electron enter the island (1.), it traps the electron with a positive charge (2.). When the electron leaves the island (3.), the demon switches back a negative charge (4.). Image: Jonne Koski.

In 1867, Scottish physicist James Clerk Maxwell challenged the second law of thermodynamics according to which entropy in a closed system must always increase. In his thought experiment, Maxwell took a closed gas container, divided it into two parts with an inner wall and provided the wall with a small trap door. By opening and closing the door, the creature – ‘demon’ – controlling it could separate slow cold and fast warm particles to their respective sides, thus creating a temperature difference in contravention of the laws of thermodynamics.

On theoretical level, the thought experiment has been an object of consideration for nearly 150 years, but testing it experimentally has been impossible until the last few years. Making use of nanotechnology, scientists from Aalto University have now succeeded in constructing an autonomous Maxwell’s demon that makes it possible to analyse the microscopic changes in thermodynamics. The research results were recently published in Physical Review Letters. The work is part of the forthcoming PhD thesis of MSc Jonne Koski at Aalto University.

‘The system we constructed is a single-electron transistor that is formed by a small metallic island connected to two leads by tunnel junctions made of superconducting materials. The demon connected to the system is also a single-electron transistor that monitors the movement of electrons in the system. When an electron tunnels to the island, the demon traps it with a positive charge. Conversely, when an electron leaves the island, the demon repels it with a negative charge and forces it to move uphill contrary to its potential, which lowers the temperature of the system,’ explains Professor Jukka Pekola.

What makes the demon autonomous or self-contained is that it performs the measurement and feedback operation without outside help. Changes in temperature are indicative of correlation between the demon and the system, or, in simple terms, of how much the demon ‘knows’ about the system. According to Pekola, the research would not have been possible without the Low Temperature Laboratory conditions.

‘We work at extremely low temperatures, so the system is so well isolated that it is possible to register extremely small temperature changes,’ he says.

‘An electronic demon also enables a very large number of repetitions of the measurement and feedback operation in a very short time, whereas those who, elsewhere in the world, used molecules to construct their demons had to contend with not more than a few hundred repetitions.’

The work of the team led by Pekola remains, for the time being, basic research, but in the future, the results obtained may, among other things, pave the way towards reversible computing.

‘As we work with superconducting circuits, it is also possible for us to create qubits of quantum computers. Next, we would like to examine these same phenomena on the quantum level,’ Pekola reveals.

J. V. Koski, A. Kutvonen, I. M. Khaymovich, T. Ala-Nissilä and J. P. Pekola: On-chip Maxwell’s demon as an information-powered refrigerator.

The abstract of the article can be read at

Check also Sebastian Deffner’s Viewpoint: Exorcising Maxwell’s Demon at


See also, how Maxwell’s demon converts information to energy with the help of nanotechnology.

Written by physicsgg

January 14, 2016 at 12:47 pm

Physics ‘demon’ reveals fundamental heat of forgetting

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Read also: Wiping data will cost you energy

by Stephen Battersby
WE’RE used to the waste heat produced by electrical wires and car brakes. Not so familiar is the heat created by erasing a digital memory. Now an experiment inspired by a metaphorical demon has measured this fundamental heat, which will one day impose a limit on the power of computers.

Maxwell’s demon, named after the 19th-century physicist James Clerk Maxwell, is a conundrum that seems to break a basic law of physics by creating a perpetual motion machine. Maxwell reasoned that his demon could control a gate dividing a box of gas molecules, some moving fast, others slow. By opening the gate at opportune moments, the demon could fill one side of the box with hot gas, the other with cold, creating a temperature difference. That difference could drive an engine, producing useful work without appearing to expend enough energy.

In 1961, Rolf Landauer proposed that the key to the conundrum was the demon’s memory. As the creature gathers information on the motion of molecules, it must erase a previous memory. Landauer suggested that the process of erasure dissipates heat. This expended heat could balance out the useful work gained by the demon and ensure it does not, in fact, get something for nothing.

Not everyone agreed with this explanation. Now Eric Lutz of the University of Augsburg in Germany and colleagues have shown that there is indeed a minimum amount of heat produced per bit of erased data. This so-called Landauer limit is proof that the demon does not get a free lunch. “We exorcise the demon,” says Lutz.

Rather than bell, book and candle, the “exorcists” use a laser that can set the position of a small glass bead. The laser is focused to give the bead two stable positions, left and right or 0 and 1. The resulting one-bit memory can store a 0 or 1, but memories are always erased by resetting to 0. The team found that the heat generated by erasing the bit is never less than the Landauer limit (NatureDOI: 10.1038/nature10872).

That has deep implications for the microchip industry, says Lutz. Right now, chips produce about 1000 times more heat per bit than the limit, due to resistance in their wires. Chipmakers are working on this but there will come a point where it can be reduced no more. “Silicon-based technology is predicted to attain the Landauer limit in 20 to 30 years,” says Lutz. Then the ability to squeeze ever more bits on a chip will depend on finding better ways to cool them, as they glow with the fundamental heat of forgetting…..
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Written by physicsgg

March 8, 2012 at 12:36 pm

Posted in Thermodynamics

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Maxwell’s Demon and Data Compression

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Akio Hosoya , Koji Maruyama , Yutaka Shikano

The protocol of data compression for demon’s memory. The dashed blocks express the trivial initial memory state “0” after data compression

In an asymmetric Szilard engine model of Maxwell’s demon, we show the equivalence between information theoretical and thermodynamic entropies when the demon erases information optimally. The work gain by the engine can be exactly canceled out by the work necessary to reset demon’s memory after optimal data compression a la Shannon before the erasure…..
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Written by physicsgg

October 24, 2011 at 6:53 pm