Maxwell’s demon in the generation of an intense and slow guided beam

We analyze quantitatively the generation of a continuous beam of atoms by the periodic injection of individual packets in a guide, followed by their overlapping. We show that slowing the packets using a moving mirror before their overlapping enables an optimal gain on the phase space density of the generated beam. This is interpreted as a Maxwell’s demon type strategy as the experimentalist exploits the information on the position and velocity of the center of mass of each packet.

Figure 1

(Color online) Schematic representation of the generation of a continuous beam by injecting packets into a guide (a), and by slowing them with a moving mirror (velocity $V$) before their overlapping (b).

Figure 2

(Color online) Representation in the single-particle phase space of one-dimensional atomic packets periodically injected in a guide (a) in the absence of slowing and (b) in the presence of slowing with the mirror moving at a velocity $V$ (dashed line). For a sufficiently long propagation distance, packets have merged and the thermal equilibrium for the corresponding beam is reached.

Figure 3

(a) The optimal mirror velocity $z^{*}\left(y\right)=V^{*}∕v_i$ normalized to $v_i$ is plotted as a function of the dimensionless parameter $y=\Delta v∕v_i$, and (b) the corresponding maximum phase space density $R_{\max }^{*}=R_{\max }\mathbf{(}y,z^{*}\left(y\right)\mathbf{)}={\rho }^{\prime }∕{\rho }_p$ of a beam generated from the packet after their optimal slowing down and normalized to the packet initial phase space density, is plotted as a function of $y$.