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> Can entropy ever be reversed?

I might not be understanding the science correctly, but due to the specific phrasing of the question, would "Sure--here's a schematic for an LED that converts waste heat back into photons[1]" be an acceptable answer?

[1] http://www.physorg.com/news/2012-03-efficiency.html (Previously discussed on HN)

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It uses energy to do so— just like a heat pump can heat your home with greater output than electrical input, but not no electrical input.

The more exciting detail is that computation itself doesn't increase entropy, at least not if reversible computing is use. Only errors or, rather, their correction do... So things may be more rosy than you might guess: http://arxiv.org/abs/quant-ph/9908043

Not really; it's clear from Asimov's story that the question is about a closed system. The abstract for the paper you cited implies the led was externally heated, acting as a thermo-couple. The closed-system efficiency was still <100%.

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