Improvement by laser quenching of an ‘atom diode’: a one-way barrier for ultra-cold atoms

Abstract

Abstract. Different laser devices working as "atom diodes" or "one-way barriers" for ultra-cold atoms have been proposed recently. They transmit ground state level atoms coming from one side, say from the left, but reflect them when they come from the other side. We combine a previous model, consisting of the stimulated Raman adiabatic passage (STIRAP) from the ground to an excited state and a state-selective mirror potential, with a localized quenching laser which produces spontaneous decay back to the ground state. This avoids backwards motion, provides more control of the decay process and therefore a more compact and useful device.PACS numbers: 32.80. Pj, 42.50.Vk, Atom optics is devoted to the understanding and control of coherent atomic waves interacting with electromagnetic fields or material structures, and much of its current development is inspired by analogies with electronics and photonics. Many optical elements such as lenses, mirrors, splitters, or interferometers have been proposed and demonstrated [1,2]. Ultra-cold atoms can also be transported coherently along waveguides, and this opens up the possibility to develop atom circuits or chips [3,4,5]. To that end, basic circuit elements and operations have to be implemented; among them, an important one is the "diode" or "one-way barrier", which lets atoms, typically in the ground state, pass in one direction but blocks them in the opposite direction, within a "working" velocity range. Such a device may have a significant impact for trapping and cooling in waveguides or other geometries. In a series of recent papers [6,7,8,9], the present authors and coworkers have proposed and analyzed the properties of different laser devices and atom-level schemes which achieve on paper the goal of oneway transmission. The possibility to use them for phase-space compression in a cooling procedure complementary to the existing ones [7,8] is an exciting prospect that deserves

Single-photon atomic cooling

“…Therefore the Zeeman Hamiltonian (Eq. 2.20) can be written in a more useful form, in this case, by taking the projection of J and I along F 21) where the terms in the angled brackets refer to an expectation value. This can be written more compactly as 22) where B has been taken alongẑ and g F is given by…”

“…the increase in potential energy of the atom [21]. This is completely analogous to the fact that the work done by an ideal elevator is equal to the change in the potential energy of its occupants.…”

Optimizing the catching of atoms or molecules in two-dimensional traps

“…An atom diode is a device which can be passed by the atom only in one direction whereas the atom is reflected if coming from the opposite direction. Such a device has been studied theoretically [5][6][7][8] and also experimentally implemented as a realization of a Maxwell demon [9,10].…”

“…If the atom crosses the diode from left to right then this is an irreversible process, the atom cannot go back, that is, the atom is caught between the diode and the trap wall. Note that the implementations of an atom diode presented in [3,[5][6][7][8] are designed in such a way that the internal state of the atom is changed during the passing of the diode but it will be restored at the end in such a way that the atom is in the same internal state before and after crossing the diode. The diode, which is in principle a semipenetrable barrier, behaves like a wall for the captured atom and continues moving to the left without changing its velocity.…”

“…In an ideal setting, the walls of the box consist of atom diodes: If the atom has crossed a wall of the box and the kinetic energy of the atom is lower than the threshold energy of the "diodic" wall (called the threshold energy of the box in the following) then the atom is irreversibly caught by the box. Note that in the ideal case the caught atom is in the same internal state as before the catching (see also [5][6][7][8]). In such a way, a similar effect as shown in Fig.…”