Illustration for article titled Convert Information into Energy, Just Add Demon

Researchers in Tokyo have taken a physics law-breaking thought experiment from an 18th century Scottish theoretical physicist and made it a reality, converting energy into information using Maxwell's Demon.


James Clerk Maxwell was a Scottish mathematician and theoretical physicist who wanted to prove that the second law of thermodynamics only held statistical certainty, and could be broken. The second law states that differences in temperature, pressure, and chemical potential will equilibriate over time in a closed system.

To prove his point, Maxwell created a demon.

This imaginary demon guarded a door. The demon would allow faster-moving hot molecules of gas pass through one way, while only slower moving cold molecules could pass through the other side. One side of the door would continuously grow hotter, gaining energy, while the other cooled.


McDonald's would later attempt this with the doomed-to-fail McDLT.

The demon in Maxwell's experiment essentially took the information it had regarding the speed of molecules and converted it into energy. The demon expended no energy on his own . . . it merely opened or closed a pathway based on the information it had.

Now physicist Masaki Sano and colleagues at the University of Tokyo have taken this law-breaking thought experiment and made it a reality, making a bead climb a spiral staircase using the power generated by information.

To create a real-life version of the demon experiment, Sano and his colleagues placed an elongated nanoscale polystyrene bead, which could rotate either clockwise or anticlockwise, into a bath of buffer solution. The team applied a varying voltage around the bead, making it progressively harder for the bead to rotate a full 360 degrees in the anticlockwise direction. This effectively created a "spiral staircase" that was harder to "climb up" in the anticlockwise direction than to "fall down" in the clockwise direction, says Sano.


By itself the bead would mainly move clockwise, or down the stairs, every once in awhile making a random jump anticlockwise, or upstairs.

Then Sano and colleagues introduced their own version of Maxwell's Demon. A camera analyzed the movements of the bead, and on those rare occasions when it would move anticlockwise the electrical current shifted slightly, making it harder to turn back clockwise. Slowly but surely the bead would climb the staircase .


While the experiment isn't actually breaking the second law of thermodynamics, it does demonstrate how information can be used as a means to transfer energy. Perhaps one day such a device could be used to generate energy on a nanoscopic scale, powering the microscopic machines of the future with nothing more than a little knowledge.

"This is a beautiful experimental demonstration that information has a thermodynamic content," says Christopher Jarzynski, a statistical chemist at the University of Maryland in College Park. In 1997, Jarzynski formulated an equation to define the amount of energy that could theoretically be converted from a unit of information2; the work by Sano and his team has now confirmed this equation. "This tells us something new about how the laws of thermodynamics work on the microscopic scale," says Jarzynski.


Demonic device converts information to energy [Scientific American]

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