# Maxwell's demon demonstration turns information into energy

(PhysOrg.com) -- Scientists in Japan are the first to have succeeded in converting information into free energy in an experiment that verifies the "Maxwell demon" thought experiment devised in 1867.

Maxwell's demon was the invention of Scottish mathematician and James Clerk Maxwell, who wanted to contradict the (although the name was given to the imaginary being later). This law implies it is not possible to invent a perfect heat engine able to extract heat from a hot reservoir and use all the heat to perform work, because some of the heat must be lost to a cold reservoir.

Maxwell imagined a box containing a gas at a particular temperature (or pressure). In any gas some molecules are hotter (moving faster) and some are cooler (moving slower) than the average. In Maxwell’s thought experiment a partition with a small trapdoor is placed in the box, and the trapdoor is guarded by the imaginary being who, without expending energy, selects which molecules go through to the other side.

The demon, for example, could allow only hotter molecules to remain on the right side, or pass through to the right side, while the cooler than average molecules are allowed into the left side. The end result is that all the hot molecules end up on one side of the box, which is therefore warmer than the other side containing only cool molecules. The demon has essentially converted a mixed gas (disordered state or higher entropy) to separated gases (ordered state or lower entropy), apparently violating the second law of thermodynamics which also says entropy in an isolated system should not decrease.

In Maxwell’s thought experiment the demon creates a temperature difference simply from about the gas molecule temperatures and without transferring any energy directly to them. The temperature difference in the box could then be used to run a heat engine, with heat flowing from the hot end to the cold end, which also appears to violate the second law of thermodynamics.

In a now-classic 1929 paper on Maxwell’s demon, Hungarian physicist Leo Szilard showed that the thought experiment does not actually violate the laws of physics because the demon must exert some energy in determining whether molecules were hot or cold.

Until now, demonstrating the conversion of information to energy has been elusive, but University of Tokyo physicist Masaki Sano and colleagues have succeeded in demonstrating it in a nano-scale experiment. In a paper published in Nature Physics they describe how they coaxed a Brownian particle to travel upwards on a "spiral-staircase-like" potential energy created by an electric field solely on the basis of information on its location.

The team observed the particle using a high-speed camera. The particle had some thermal energy and moved in random directions. When it was moving up the staircase they allowed it to move freely, but when it moved down the staircase they blocked its movement via a virtual wall created by an electric field. The virtual wall therefore acted like a Maxwell’s demon, only allowing the particle to move in one direction, but not forcing or pushing it.

As the particle traveled up the staircase it gained energy from moving to an area of higher potential, and the team was able to measure precisely how much energy had been converted from information. The experiment did not violate the second law of thermodynamics because energy was consumed in the experiment by the apparatus used, and by the experimenters themselves, who did work in monitoring the particle and adjusting the voltage, but Sano said the experiment does demonstrate that information can be used as a medium for transferring energy.

The results also verified the generalized Jarzynski equation, which was formulated in 1997 by statistical chemist Christopher Jarzynski of the University of Maryland. The equation defines the amount of that could theoretically be converted from a unit of information.

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Could Maxwell's Demon Exist in Nanoscale Systems?

More information: Experimental demonstration of information-to-energy conversion and validation of the generalized Jarzynski equality, Nature Physics, Published online: 14 November 2010. doi:10.1038/nphys1821

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Nov 15, 2010
Correct me if I'm wrong, but it sounds like this isn't "converting information to energy", it's just transferring energy from one place to somewhere else, like everything else that happens in the universe.

Nov 15, 2010
The god (or demon) is in the details and definitions. And with the details and definitions used by these researchers, you are indeed wrong.

Nov 15, 2010
I am curious how this experiment differs from an article found at the following link:

Could Maxwell's Demon Exist in Nanoscale Systems?

http://www.physor...343.html

Information and quantum fluctuations seem to go hand in hand.

Nov 15, 2010
The god (or demon) is in the details and definitions. And with the details and definitions used by these researchers, you are indeed wrong.

Okay, well explain how then.

Nov 15, 2010
There are spin characteristics of some molecules that are unipolar (diode like in the point of interaction) and/or non-neutral (not specifically balanced), and therefore.... their interactives can and will seemingly violate the second THEORY of thermodynamics.

It's almost an argument on semantics, but not quite. And there's the rub.

Nov 15, 2010
This all seems to me to be "much ado about nothing". Why do they want to do this? Given the empirical reality and theoretical underpinnings of entropy as context for all that ever happens, what are these guys trying to prove? I know of only two apparent exceptions to the universal principal of "everything has a cost", and they don't apply in the context of this article. [the first is life itself, because your mother paid the price there; the second is the 'power of positive thinking', because your brain is already expending the energy, so nothing is gained by choosing to be negative, but much is gained by choosing to be positive.]

The fact is 'information' is ultimately an emergent property of structures which always have to be somewhere and made out of something. Those structures required energy expenditure to get to be where they are and the shape they are. Amen!

Nov 15, 2010
Living things increase order in themselves at the cost of increasing disorder in the environment.
Where's the evidence that "choosing to be positive" violates thermodynamics?

Nov 15, 2010
eventually the particle would lose its initial energy by repeated bouncing against the staircase? Or does it get enough from the Zero point field to get going (for example in a circular staircase loop)??? In that case the Zero point energy field that accounts for Brownian motion and its virtual particles would pay for it and the zero point field would "cool"down?

Nov 15, 2010
Think of a room divided in half by a "one way" ceiling. The room is full of bouncing balls. Balls that are only bouncing a little don't make it through the ceiling. Those trapped above the ceiling are bouncing lower, but have the excess stored as potential energy that will be returned to kinetic energy if the one-way ceiling is removed.

Now bring that back to the context of molecules and heat. You have created two reservoirs, hot and cold, with a temperature differential that can be used to do work. You created this energy only by employing the "ceiling's" (Maxwell's demon's) information. Information to energy. The difference in this research since the last installment mentioned by @TM above is they actually did it.

Nov 15, 2010
Seems to me the energy it takes to create and maintain the electrical field that acted as the "demon" violates the thought experiment. It takes energy to sort out the low energy particles.

Nov 15, 2010
@Doug, only if the amount of energy used to maintain the "demon" is directly related to the energy gain from information. If the two are unrelated, generating energy from information is just beyond our reach technologically, but very possible.
*start crazy talk*
What if the "boundary" of our universe had a "demon" filtering anti-matter explaining CP violation?

Nov 15, 2010
We can burn books to get energy. Maybe one day there is a button on Kindle that lets one turn a crappy novel into pure energy.

Nov 15, 2010
A sentient "Demon" that can sort out or flick switches to allow things to pass... yep, still sounds as stupid as it did when I studied it years and years ago. The little "Demon" needs energy to operate. What the hell is up with people missing the concept of a closed system when it comes to thermodynamics. ARRGGHHHHhhhh... IT'S PROBABLY ONE OF THE MOST POINTLESS THOUGHT EXPERIMENTS I CAME ACROSS DURING MY YEARS OF STUDY.

Sorry, but yeah... it's ridiculous.

So then, who has actually read this paper? Where is the energy coming from to determine the direction of the particle and the energy to create the electrical field.

From the wording in this article it sounds scarily like the people doing the experiment actually used their own eyes and brains to make the decision of when to flick a switch to block the particle... if that's the case then good luck trying to calculate the energy used by their brains that was related to the decision path.

Nov 15, 2010
.."entropy in an isolated system should not decrease."
The average entropy of an isolated system is always lower than the maximum possible entropy (the difference is greater for an ever larger spatial extension) and so, by choosing the maximum entropy configuration as my initial condition, entropy will always fall in an isolated system...All classic experiments choose a low (often lowest) entropy configuration as the initial condition...

Nov 16, 2010
I am giving up on Maxwell's Demon. It is like trying to create a perpetual motion machine. Not even God can do that!

Nov 16, 2010
Good call on putting energy into electric barrier, does this electric field work like a spatially controlled asymmetric Cassimir force?

Nov 16, 2010
Think of the demon as a ratchet with a little paddle attached, it can only turn in one direction. Sometimes, by pure chance, a particle hits the correct side of the paddle and turns the ratchet one notch on, repeat.

Nov 16, 2010
Think of the demon as a ratcheted wheel with a little paddle attached, it can only turn in one direction. Mostly particles will be hitting both sides of the paddle, but sometimes, by pure chance, a particle hits just the correct side of the paddle and turns the ratchet one notch on, repeat.

Nov 16, 2010
A sentient "Demon" that can sort out or flick switches to allow things to pass... yep, still sounds as stupid as it did when I studied it years and years ago.

I could say the same about talking monkeys, but that would be rude. This isn’t about open/closed systems because the total energy is constant here (neglecting the energy required to feed the demon, of course). This is about entropy, taking a sample of randomly moving particles and sorting those with one kind of motion from another, to produce an energy differential…which can then be used to do work. If it takes less energy to feed the demon than the potential energy differential you create with it, you win.

But there are better ways to get useful work out of thermal energy (imagine being able to get electrical energy from the air simply by cooling it down). This could be done with nanotech, by creating a sheet with nanomagnets on springs inside nanoinductors that are set oscillating by the collisions of air molecules.

Nov 16, 2010
@MaxwellsDemon

The odds of the demon creating work are very minute, however the odds are there.
Yes, there are more reliable ways to create useful work.
Does that violate the 2nd Law; the answer must be yes, once in a great, great while.

Good work on coming up with ideas involving nanotech.

What I do not understand is the philosophy behind the word 'information.'

Is not everything made out of pure energy. Why would information be different?
It sounds to me like a conversion of one form of energy to another.

Nov 16, 2010
Phideaux,
Living things increase order in themselves at the cost of increasing disorder in the environment.
Where's the evidence that "choosing to be positive" violates thermodynamics?

There is no 'violation' of thermodynamics.

The point is that the human brain is always operating, even while we are asleep, so it makes sense to use that energy for thoughts that are life enhancing rather than despondent and destructive. That is a 'no brainer' if anything is :-)

Although various figures get touted about, it is common to see 20% given as the proportion of our energy intake which is used within the brain. That is a huge amount when compared to the size and mass of the brain in relation to the rest of the body [1.5 kg of brain as against 72 kg total body weight for me. My understanding is that most of this energy goes to into pumping sodium and potassium ions back across the the cell membrane after a depolarisation wave has gone through.

Nov 19, 2010

Is not everything made out of pure energy. Why would information be different?
It sounds to me like a conversion of one form of energy to another.

Yes, that's exactly what the article says. They also say, at the very end: "The results also verified the generalized Jarzynski equation, which was formulated in 1997 by statistical chemist Christopher Jarzynski of the University of Maryland. The equation defines the amount of energy that could theoretically be converted from a unit of information."

As for people talking about violations of the 2nd law of thermodynamics ... the article specifically points out that there is no violation ... energy is expended by the apparatus and the researchers themselves. The point is the conversion of energy from information into potential energy within the system in the form of the elevation of the particle on the helical "staircase".

Nov 19, 2010
@Auxon

The headline to the article should have been more exciting, like: Information and Energy Proven To Be The Same, or a more eye catching headline.

This experiment is really big news. It provens energy and information/communication are of the same just in the event someone wanted to know or questioned the idea.

I agree with the blogger 'MaxwellsDemon' above that the 2nd law could be violated (by accident/by chance or however it was stated).
In order for that to happen, there would have to be a reason why.

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