Single-Photon Atomic Cooling - Raizen Lab - The University of ...

y the one-way-wall through an irreversible step. The one-way-wall continues
to sweep until all atoms have encountered it, been cooled and returned to the
center of the conservative potential. This general technique is applied, for the
first time, to the specific case of cooling magnetically trapped 87 Rb, and details
of its specific implementation and results are given in Ch. 4.
1.5 Single-Photon Cooling as a Maxwell’s Demon
In 1867 James Clerk Maxwell proposed the notion of a “very observant
and neat-fingered being” and wondered if under certain circumstances it could
possibly violate the second law of thermodynamics [24]. He imagined such a
creature, later given the honorable designation of a “Maxwell’s Demon” by
Lord Kelvin [25], as operating a trap door separating two halves of a vessel
filled with gas molecules initially in thermal equilibrium. He argued that if the
demon sensed the velocity of molecules at they approached and directed fast-
moving molecules into one half of the vessel and slow-moving molecules into
the other half it would cause a temperature differential “without expenditure
of work.” A second version of the demon would simply let molecules pass
into one half of the vessel but never out of it, thus developing a pressure
differential. Such apparent violations of the second law of thermodynamics
spurred intense interest and research into “exorcising” such demons, in other
words demonstrating that they do not violate any microscopic or macroscopic
law of physics.
One enduring notion, originally proposed by Szilard [26], and later
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