Maxwell's Demon: Cooling of Atoms and Efficient Isotope Separation

Stephen Travis Bannerman

Tsung-Yao Wu, Aishwarya Kumar, Felipe Giraldo +1 more

M. Jerkins, Isaac Chavez, Uzi Even +1 more

Isotope separation is one of the grand challenges of modern society and holds great potential for basic science, medicine, energy, and defense. We consider here a new and general approach to isotope separation. The method is based on an irreversible change of the mass-to-magnetic moment ratio of a particular isotope in an atomic beam, followed by a magnetic multipole whose gradients deflect and guide the atoms. The underlying mechanism is a reduction of the entropy of the beam by the information of a single-scattered photon for each atom that is separated. We numerically simulate isotope separation for a range of examples, including lithium, for which we describe the experimental setup we are currently constructing. Simulations of other examples demonstrate this technique's general applicability to almost the entire periodic table. We show that the efficiency of the process is only limited by the available laser power, since one photon on average enables the separation of one atom. The practical importance of the proposed method is that large-scale isotope separation should be possible, using ordinary inexpensive magnets and the existing technologies of supersonic beams and lasers.

Mark G. Raizen

Recent work provides a general two-step solution to trapping and cooling of atoms. The first step is magnetic stopping of paramagnetic atoms with the use of a sequence of pulsed fields. The second step is single-photon cooling, which is based on a one-way barrier. This cooling method is related intimately to the historic problem of "Maxwell's Demon" and subsequent work by L. Szilard. Here, I discuss the connections between single-photon cooling and information entropy. I also outline future application of these methods to fundamental tests with hydrogen isotopes.

D. Steck

Stephen Travis Bannerman, Gabriel Price, Kirsten Viering +1 more

We demonstrate a general and efficient informational cooling technique for atoms that is an experimental realization of a one-dimensional Maxwell's demon. The technique transfers atoms from a magnetic trap into an optical trap via a single spontaneous Raman transition that is discriminatively driven near each atom's classical turning point. In this way, nearly all of the atomic ensemble's kinetic energy in one dimension is removed. We develop a simple analytical model to predict the efficiency of transfer between the traps and provide evidence that the performance is limited only by particle dynamics in the magnetic trap. Transfer efficiencies up to 2.2% are reported. We show that efficiency can be traded for phase-space compression, and we report compression up to a factor of 350. Our results represent a 15-fold improvement over our previous demonstration of the cooling technique.